Patent Description:
The re-use of medical equipment that is intended to be single-use is a source of great concern, because such re-use can lead to the transfer of contagious diseases. Syringes comprising a syringe barrel having an elongate tip and a fluid passageway, which is typically the Lumen of a needle attached to the syringe through which fluid exits the syringe, are an example of such devices. Such syringes further comprise a plunger having proximal end upon which a user applies force to advance the plunger into the barrel and a proximal end with a distal portion. After use, some amount of fluid typically remains in what is referred to as dead space between the distal portion and the elongate tip of the barrel.

Attempts have been made to prevent the re-use of syringes by providing breakable plunger rods as part of the syringe assembly, examples of which being disclosed in <CIT>) and in United States Patent Publication Number <CIT>). Such breakable plunger rod assemblies provide a breakable connection between the main body of the plunger rod and the proximal distal portion. Such breakable connections possess sufficient structural integrity to resist breakage during normal use, but break upon application of additional force. Thus, alter injection of the liquid contents of the syringe into a patient or into a suitable container or device such as through the pierceable septum of a catheter connector, a user applies additional force on the thumb press of the plunger rod. This additional force causes the breakable connection to shear, mechanically disconnecting the main body of the plunger rod from the distal portion, and hence disabling further use of the syringe.

After the breakable connection activates (i.e., breaks), the main body of the plunger rod moves forward at a relatively high speed and strikes the distal portion. This creates a contact impulse that compresses the distal portion and forces out fluids that remain within the dead space between the distal portion and the passageway of the elongate tip of the medical device. These fluids can be expelled at high speeds, resulting in a spray from the tip of the opening or lumen if a needle is attached to the syringe. Such a spray poses a risk of spreading contaminating fluids or blood.

It would be therefore desirable to provide syringes and breakable plunger rod assemblies that mitigate the risk of liquids spraying from the nozzle of a medical device when the plunger rod is disabled.

<CIT> discloses a single-use syringe comprising a barrel having a proximal end, a distal end and an inside surface, and a plunger rod having a proximal portion and a distal portion connected by a disengageable connection.

Preferred embodiments are included as dependent claims.

Embodiments of the invention pertain to a syringe including a barrel and a plunger. The barrel includes a barrel having a fluid chamber, an inside surface, a proximal end, a distal end and a tip extending from the distal end having a passageway in fluid communication with the chamber. According to the invention, the plunger includes a proximal portion connected by a breakable connector to a distal portion. The proximal portion may have a flange upon which a user may push along a longitudinal centerline of the plunger rod. In one or more embodiments, the distal portion has a distal end with a stopper that provides a slidable seal with the inside surface of the barrel for expelling fluids from the passageway. The breakable connection breaks when the force applied by the user exceeds a breaking force. In one or more embodiments, an impulse reduction system is disposed between the stopper and the flange to reduce the contact impulse that occurs between the proximal portion and the distal portion when the breakable connection breaks.

According to the present invention, the impulse reduction system comprises a first braking surface that is disposed on the proximal portion, and a second braking surface that is disposed on the distal portion. The braking surfaces are designed to slidingly engage with each other to create a motion-resistive force between the proximal portion and the distal portion. In another embodiment, the first braking surface is sloped with respect to the longitudinal centerline of the plunger rod. In another embodiment, the second braking surface is sloped with respect to the longitudinal centerline of the plunger rod. The surfaces may be roughened to increase the coefficient of friction between the surfaces, and hence the braking force.

In another example not being part of the present invention, the impulse reduction system comprises an elastic element, such as a spring or similar device, disposed within a gap that separates the proximal portion from the distal portion along the longitudinal centerline.

Before describing several exemplary embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description and drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways.

A convention employed in this application is that the term "proximal" denotes a direction closest to a practitioner, while the term "distal" denotes a direction furthest from the practitioner.

According to a one embodiment of the invention depicted in <FIG> and <FIG>, a syringe <NUM> includes a barrel <NUM> having an internal surface <NUM> defining a fluid chamber <NUM>, a distal end <NUM>, a proximal end <NUM>, a distal tip <NUM>, and a breakable or collapsible plunger rod <NUM>. The collapsible plunger rod <NUM> may be slidably disposed within the barrel <NUM>. The plunger rod <NUM> includes a distal portion <NUM>, a proximal portion <NUM> and a stopper <NUM> connected to the distal portion <NUM>. The distal portion <NUM> and the proximal portion <NUM> are connected to each other via collapsible or breakable connection <NUM>. The stopper <NUM> is slidably positioned in fluid tight engagement with the internal surface <NUM>, and is able to slide distally and proximally along longitudinal centerline <NUM>. By moving the plunger rod distally, the stopper <NUM> may force fluids out of fluid passage way or opening <NUM> in the distal tip <NUM>. By moving proximally, the stopper <NUM> may draw fluids through the fluid passageway <NUM> and into the fluid chamber <NUM>. It will be appreciated by those skilled in the art that the distal tip <NUM> of the syringe <NUM> may be releasably or permanently connected to a needle assembly via a hub <NUM> as is known in the art. Such needle assemblies include, but are not limited to, Luer lock type needle assemblies and Luer slip type needle assemblies. It is further within the purview of this invention to include a needle assembly having a one piece construction wherein the cannula and the hub are formed of one piece.

A proximal end of the proximal portion <NUM> may include a thumb flange <NUM> that a user may push to move the plunger rod <NUM> and stopper <NUM> distally, or pull upon to move the plunger rod <NUM> and stopper <NUM> proximally. An impulse reduction system <NUM> is disposed on the plunger rod <NUM> between the stopper <NUM> and the flange <NUM> to reduce the contact impulse between the proximal portion <NUM> and the distal portion <NUM> generated when the breakable connection <NUM> breaks. Although <FIG> and <FIG> show an impulse reduction system <NUM> that utilizes friction surfaces, it will be appreciated that any suitable impulse reduction system <NUM> may be utilized within the syringe <NUM>.

As shown in <FIG>, the breakable connection <NUM> may include protuberances <NUM> that are transverse to the longitudinal centerline <NUM>, and which connect overlapping regions of the proximal portion <NUM> with corresponding regions on the distal portion <NUM>. <FIG> show the collapsible plunger rod <NUM> prior to the breakable connection <NUM> breaking. <FIG> and <FIG> show the collapsible plunger rod <NUM> alter the breakable connection <NUM> has been activated. The protuberances <NUM> are manufactured to withstand typical-use shear forces generated when a user draws fluids into fluid passageway <NUM>, or expels them through opening <NUM> during normal use in medical procedures. However, upon the application of a certain breaking force indicated by arrow F in <FIG>, which should not be so small as to risk unintentional activation of breakable connection <NUM> during application of force during normal use, nor too great as to place undue strain on the user, the breakable connection <NUM> activates. That is, when a user presses down upon thumb flange <NUM> with the intent to disable the syringe <NUM> using an additional force, the protuberances <NUM> shear away from distal portion <NUM>. Thus, the breaking force is the total force that includes the force applied under normal use plus some additional force required to break the breakable connection. As a result, proximal portion <NUM> mechanically disconnects from distal portion <NUM>, collapsing the plunger rod, effectively disabling distal portion <NUM> and thus rendering syringe <NUM> unusable.

The breaking force depends on various dimensions of the syringe barrel and plunger, the viscosity of the liquid being delivered and the mechanical and hydraulic forces encountered by the filling and delivery process. If the breakable connection is too weak, the proximal and distal portions will separate during normal use of the syringe and if the force required to break the breakable connection is too high the user may not be able to easily break the breakable connection as intended. The skilled artisan can select the appropriate materials and/or connections to provide the proper breaking force to cause the connection to break and the plunger rod to collapse for a particular syringe design and/or use.

To prevent spraying from fluid passageway <NUM> or lumen of a needle attached to the syringe that would otherwise result from most distal end <NUM> of proximal portion <NUM> impacting distal portion <NUM> after activation of breakable connection <NUM>, plunger rod <NUM> is provided an impulse reduction system <NUM>. As shown in <FIG>, one or more first braking surfaces <NUM> may be provided on the proximal portion <NUM>, which may be located within the distal region of the proximal portion <NUM>. The first braking surface <NUM> may be slightly sloped with respect to the longitudinal centerline <NUM> so that the first braking surface <NUM> becomes more distant from the longitudinal centerline <NUM> along the distal direction. The first braking surface <NUM> may define a relatively rough finish to increase the coefficient of friction of the first surface <NUM>. The distal portion <NUM> is provided one or more corresponding second braking surfaces <NUM>, which are aligned with the first braking surfaces <NUM>, and which may be provided within the proximal region of the distal portion <NUM>. The second braking surfaces <NUM> may also define roughened surfaces to increase their coefficients of friction. The braking surfaces <NUM>, <NUM> may be located adjacent to the breakable connection <NUM>.

As shown in <FIG> and <FIG>, when the breakable connection <NUM> activates, the proximal portion <NUM> moves along the longitudinal centerline <NUM> with respect to the distal portion <NUM>. There thus exists, immediately after activation of breakable connection <NUM>, relative motion between the proximal portion <NUM> and distal portion <NUM>, which brings the braking surfaces <NUM>, <NUM> into contact with each other. The first braking surface <NUM> thus slides against the second braking surface <NUM>. The friction developed between the first braking surface <NUM> and the second braking surface <NUM> creates a motion-resistive force between the proximal portion <NUM> and distal portion <NUM>. The wedge-shaped alignment of the first braking surface <NUM> and the second braking surface <NUM> with respect to the longitudinal centerline <NUM> causes the motion-resistive force to increase as a function of distal movement of the proximal portion <NUM> along the longitudinal centerline <NUM> with respect to the distal portion <NUM>. This motion-resistive force tends to slow the relative motion between the proximal portion <NUM> and the distal portion <NUM>, and hence acts as a shock absorber that reduces contact impulse between the proximal portion <NUM> and distal portion <NUM>.

It will be appreciated that, prior to activation of the breakable connection <NUM>, a gap <NUM>, which will be called the contact gap, exists between the proximal portion <NUM> and distal portion <NUM> through which the proximal portion <NUM> travels alter activation of the breakable connection <NUM>. Absent any sort of impulse-reduction system <NUM>, when this contact gap closes, contact between the respective surfaces that composed the contact gap leads to an impulse that compresses stopper <NUM>, and which thus leads to a sharp ejection of material from fluid passageway <NUM>. The exact location of this contact gap, and its width along the longitudinal centerline <NUM>, will depend upon the specific geometric configurations of the proximal portion <NUM> and distal portion <NUM>. For the embodiment depicted in <FIG>, and with specific reference to <FIG>, the contact gap <NUM> extends from the most distal end <NUM> of proximal portion <NUM> along the longitudinal centerline <NUM> to surface <NUM> on the distal portion <NUM>. The width, as measured along longitudinal centerline <NUM>, of contact gap <NUM> may be greater than the gap <NUM>, also measured along longitudinal centerline <NUM>, that separates the most distal end of first braking surface <NUM> from the most proximal end of second braking surface <NUM> prior to activation of the breakable connection <NUM>. As a result, the impulse reduction system <NUM> has ample distance along the longitudinal centerline <NUM> to develop a braking force that slows the relative movement between the proximal portion <NUM> and the distal portion <NUM>, and which thus reduces the contact impulse between the proximal portion <NUM> and distal portion <NUM> to reduce spraying of fluids from the fluid passageway <NUM>.

Other types of shock-absorbing mechanisms may be utilized to reduce the impulse developed between the proximal portion and distal portion. For example, an elastic element may be disposed within a gap separating the proximal portion from the distal portion. As the elastic element is compressed by the proximal portion, the elastic element reduces the speed of relative motion between the proximal portion and distal portion, and thereby reduces the contact impulse between the proximal portion and the distal portion.

An example not being part of the present invention utilizing an elastic element is depicted in <FIG>. A collapsible plunger rod <NUM> is similar to the collapsible plunger rod <NUM> discussed above, having a proximal portion <NUM> connected to a distal portion <NUM> by way of a breakable connection <NUM>. A compressible elastic element <NUM> is disposed in a gap between the proximal portion <NUM> and the distal portion <NUM>. Specifically, the elastic element <NUM> is disposed adjacent to the breakable connection <NUM>, and just forward of the breakable connection in the distal direction. When the breakable connection <NUM> shears from the distal portion <NUM>, the proximal portion <NUM> begins to advance in the distal direction. As the proximal portion <NUM> advances, it compresses a first arm <NUM> of the elastic element towards a second arm <NUM> of the elastic element. The elastic element <NUM> creates a force that resists this compression, and which thus slows the forward velocity of the proximal portion <NUM>. The elastic element <NUM> thus acts as a shock absorber that reduces the shock associated with the activation of the breakable connection <NUM>, and which thus reduces the contact impulse of the proximal portion <NUM> impacting the distal portion <NUM>.

An alternative example not being part of the present invention utilizing elastic elements as shock absorbers is depicted in <FIG>. A collapsible plunger rod <NUM> utilizes springs <NUM> disposed in gaps between proximal portion <NUM> and distal portion <NUM> to reduce the contact impulse of the proximal portion <NUM> striking the distal portion <NUM> when the breakable connection <NUM> activates. In particular, the springs <NUM> may be disposed proximally adjacent to the breakable connection <NUM>. Of course, for both embodiments depicted in <FIG> and <FIG>, any suitable elastic device or devices may be used to slow the relative motion between the proximal portion and the distal portion.

It is within the purview of the present invention to include plunger rods and stoppers which are separately fonned or integrally formed of the same material or different materials such as in two-color molding, or separately formed of the same or different materials and joined together by mechanical means, adhesives, ultrasonic welding, heat sealing or other suitable means. Stoppers are preferably made of elastomeric material such as natural rubber, synthetic rubber, thermoplastic elastomers and combinations thereof. It is understood that the plunger of the present embodiment merely illustrates these many possibilities.

In use, the syringe of this embodiment can be filled from a vial, ampoule or other suitable container using known safe procedures. According to embodiments of the invention, the plunger can be moved back and forth along the barrel as many times as necessary to properly fill the syringe barrel. For example, the syringe barrel may be filled with sterile water and then the sterile water can be injected into a vial containing a lyophilized medication which is then drawn back into the syringe barrel. Many single-use syringes in the prior art only allow one proximal motion of the plunger with respect to the barrel. With these single-use syringes, once the plunger is moved in a distal direction with respect to the barrel it can no longer be withdrawn. Therefore, mixing sterile water and a lyophilized medication as described above is not possible.

Claim 1:
A syringe (<NUM>) comprising:
a barrel (<NUM>) having a fluid chamber (<NUM>), an inside surface (<NUM>), a proximal end (<NUM>), a distal end (<NUM>) and a tip (<NUM>) extending from the distal end (<NUM>) having a passageway (<NUM>) in fluid communication with the chamber (<NUM>); and
a plunger rod (<NUM>) adapted to slidingly engage the inside surface (<NUM>) of the fluid chamber (<NUM>),
the plunger rod (<NUM>) including a proximal portion (<NUM>) having a first braking surface (<NUM>), a distal portion (<NUM>) having a second braking surface (<NUM>), and a connector (<NUM>) joining the proximal portion (<NUM>) and the distal portion (<NUM>) adapted to break upon application of a breaking force to the plunger rod (<NUM>), a contact gap (<NUM>) extending between the proximal portion (<NUM>) and distal portion (<NUM>) through which the proximal portion (<NUM>) travels after activation of the breakable connection (<NUM>), wherein the second braking surface (<NUM>) slidingly engages with the first braking surface (<NUM>) to create a motion resistive force between the proximal portion (<NUM>) and the distal portion (<NUM>) upon breaking of the connector (<NUM>), characterized in that the syringes comprises a gap (<NUM>) separating the most distal end of the first braking surface (<NUM>) from the most proximal end of the second braking surface (<NUM>) along the longitudinal centerline (<NUM>) prior to activation of the breakable connection (<NUM>), wherein a width of the contact gap (<NUM>), as measured along the longitudinal centerline (<NUM>), is greater than the gap (<NUM>) measured along the longitudinal centerline (<NUM>).