Patent Application
20080033347
While this invention is satisfied by embodiments in many different forms, there are shown in the drawings and will herein be described in detail, preferred embodiments of the invention with the understanding that the present disclosure is to be considered exemplary of the principles of the invention and not intended to limit the invention to the embodiments illustrated. The scope of the invention will be measured by the appended claims and their equivalents.
Referring to
A prior art needle assembly 32 includes a cannula 33 having a proximal end 34, a distal end 35 and lumen 37 therethrough. A hub 38 includes an open proximal end 39 containing a cavity 40 and a distal end 41 attached to proximal end 34 of the cannula so that the lumen of the cannula is in fluid communication with the cavity in the hub. The needle assembly is removably attached to the syringe through frictional engagement of the interior surface of the cavity in the hub and the exterior surface of tip 27. The hub also includes radial projections 43 on its proximal end for engaging thread 31 to hold the needle assembly securely to the barrel. The prior art syringe assembly further includes a resilient stopper 44 connected to an elongate plunger rod 45.
Liquid in a syringe barrel can experience very high pressures during the injection process. This is especially true in the case of high viscosity medications and/or needle cannula having a lower diameter lumen. To seal the interface between the needle hub and the syringe against these high pressures, a frusto-conically shaped engagement surface 30 on tip 27 frictionally engages a frusto-conically shaped engagement surface 42 in hub cavity 40. When the diameter of the engagement surface 42 is on the small end of its tolerance range and the diameter of the engagement surface 30 of the barrel tip is on the large end of its tolerance range, it can be seen that the barrel tip will not move as far into the cavity of the needle hub thus leaving more empty space in the hub cavity. Although the seal created by the frusto-conically shaped engagement surfaces is very effective, the components must be designed to accept all anticipated tolerance variations of the barrel tip and hub cavity so that the distance the barrel engages the hub cavity will vary throughout the tolerance range thus varying the amount of unoccluded space in the hub cavity. As can be seen in
Other prior art syringe assemblies have attempted to minimize and reduce the variability of dead space by providing frusto-conically shaped engagement surfaces which are at much larger angles with respect to the longitudinal axis of the barrel to shorten the variation in the dead space based on tolerances. The best control of dead spaces can be achieved with a flat engagement surface positioned approximately at an angle 90° with respect to the longitudinal axis of the barrel. This configuration best controls dead space caused by tolerance variation, and can overcome inherent dead space in the luer slip barrel tip. However, imperfections on the mating surfaces or variations in the flatness of these surfaces can result in a seal between the hub and the barrel which may leak initially or over a period of time. Also, the quality of the seal is directly related to the amount of force applied to the hub while engaging it to the barrel.
Referring to
A needle assembly 67 includes a hub 68 having a body portion 69 including a proximal end 70, a distal end 71 and a conduit 73 therethrough. A proximally facing annular surface 74 on the body portion contacts the annular surface on the barrel forming a primary seal between the hub and the barrel. Annular surface 74 is preferably flat. The hub also includes an outwardly projecting annular sealing ring 75 sealingly engaging the circular sidewall of the collar forming a secondary seal between the hub and the barrel.
In this embodiment, the annular sealing ring is an o-ring contained in annular groove 76 around the body portion of the hub. As will be more fully explained hereinafter, the outwardly projecting annular sealing ring can be any structure which is resilient enough to deflect upon installation of the needle assembly to the barrel so that the annular sealing ring deflects upon contact with circular sidewall portion of the collar. These structures are all within the purview of the present invention. The o-ring and other structures for the annular sealing ring taught herein are merely representative of these many possibilities.
Needle assembly further includes a cannula 96 having proximal end 97, a distal end 98 preferably having a sharp distal tip 95 and a lumen 99 therethrough. The proximal end of the cannula is connected to the distal end of the hub so that the lumen is in fluid communication with the chamber in the barrel. The cannula may be integrally formed with the hub such as by injection molding using thermoplastic materials or separately formed, as in this embodiment, and attached to the hub. In this embodiment adhesive 77 is used to attach the cannula to the hub, and the cannula is made of metal, preferably stainless steel.
Structure for releasably engaging the hub to the collar including hub engaging structure on the collar and complimentary collar engaging structure on the hub is provided. In this embodiment structure for releasably engaging the hub and collar includes at least one thread 57 on an inside surface 61 of the circular shaped sidewall 59. The thread may be either right-handed or left-handed, and it also may be a multiple-lead thread. The hub includes at least one thread engaging the projection. In this embodiment, there are two thread engaging projections 78, preferably on opposite sides of the hub.
The syringe assembly may also include an elongate plunger rod 82 having a proximal end 83, a distal end 84 and a stopper 87 at the distal end of the plunger rod. A stopper is slidably positioned in fluid tight engagement with the inside surface of the barrel for displacing fluid from the chamber through the cannula by relative motion of the plunger with respect to the barrel. The stopper desirably includes a distally facing projection 88 for partially occluding the conduit in the hub when the stopper is in its distal most position inside the barrel to further reduce dead space.
The needle assembly may further include an elongate, hollow needle shield 91 having a distal end 92 and open proximal end 93 removably engaged to the hub so that the needle shield covers the cannula.
The needle assembly maybe installed or removed from the barrel by grasping the needle shield and rotating the hub in the appropriate direction to install or disengage the needle assembly. During installation, rotation of the hub will cause the needle engaging projections of the hub to follow the thread until proximally facing annular surface 74 of the hub contacts distally facing annular surface 58 of the barrel to form primary seal between the hub and the barrel. In this position, outwardly projecting annular sealing ring 75 is deflected as illustrated in
It should be noted that the proximally facing annular surface 74 when it is flat on the hub and the distally facing annular surface 58 when it is flat on the barrel need not be aligned exactly at 90° from the longitudinal axis. A broad range of angles will work with the angles of 88° to 92° being desired and 90° being preferred.
An elongate barrel 249 includes an inside surface 251 defining a chamber 252 and an open distal end 255 and a collar 256. The collar includes an inside surface 261 having at least one thread engaging projection. In this embodiment there are two thread engaging projections 262 facing inwardly for engaging thread 281 on hub 268. The components of this embodiment function similarly to the embodiment of
There are many ways to configure the hub and the collar of the barrel including a hub having an additional skirt which surrounds the collar of the syringe barrel. With this construction, the outside of the collar may include at least one thread or at least one thread-engaging projection while the inside of the hub skirt will include the other of a thread or at least one thread-engaging projection. The engagement between the hub and the collar, in all configurations, can include a thread or thread-like structure on the hub and a thread or thread-like structure on the collar. All of these structures are within the purview of the present invention and the embodiments taught hereinabove are merely representative of these many possibilities.
