Abstract:
A dental syringe system having a syringe body containing a needle assembly wherein the syringe body serves as a protective shield after medication is injected. A reusable plunger assembly pushes a slidable seal of a carpule and the needle out for medication delivery and then pulls the needle back within the syringe body after the medication is delivered. The needle assembly, syringe body, carpule carrier and carpule are disposable and the plunger is reusable.

Description:
PRIORITY APPLICATION 
     This application is related to U.S. Provisional Application Ser. No. 60/282,023 filed on Apr. 6, 2001, entitled “DENTAL SYRINGE WITH DISPOSABLE NEEDLE ASSEMBLY AND REUSABLE PLUNGER ASSEMBLY” and assigned to all the above named inventors, and incorporated by reference herein, with priority claimed for all commonly disclosed subject matter. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a dental safety syringe having a needle containment safety apparatus and method to protect medical personnel and others from the risk of accidental percutaneous needlestick injuries. 
     2. Prior Art 
     Because dental healthcare personnel are at risk of contracting diseases from accidental needle sticks a variety of safety syringes have been developed. Many of the safety syringes have a shield that is placed over the extended needle after medicine has been injected. For example Talonn et al. U.S. Pat. No. 5,522,812 has a shield that is manually placed over the end of an extended needle. Other shields are positioned by sliding a cylindrical shield down the body of the syringe, such as described in Stanners, U.S. Pat. No. 5,403,288. In such designs the hand of the person sliding the shield in place is close to the needle thereby providing some chance of a needle stick. 
     Another approach for providing a shield of protection from needle sticks is based on moving the extended needle in the proximal direction (retracting the needle) until the needle is contained within the cylindrical body of the syringe. Haber et al. U.S. Pat. No. 4,931,040 modifies the conventional carpule allowing a needle to be retracted and locked within the cylinder of the carpule. Because the Haber invention keeps a person&#39;s hand at a greater distance from the extended needle than the above slidable shield devices, the chances of a needle stick are decreased. However the complex modifications to the carpule used by Haber may make the invention too expensive. Another example of retracting the needle within the syringe is described by Sak, U.S. Pat. No. 5,501,670 but requires a special and complex needle retracting unit. 
     Hence there is a need to provide an improved dental safety syringe for healthcare personnel that provides for safe disposal and has reduced complexity and cost. 
     SUMMARY OF THE INVENTION 
     A dental safety syringe that is adapted for use with existing conventional carpules and does not have the complexity of prior art safety syringes has been invented. The novel dental safety syringe of the present invention is easy to operate and an improvement over prior art devices. 
     In accordance with the present invention a dental syringe for dispensing medication from a carpule with a proximal slidable seal and a distal seal is comprised of a carpule carrier adapted for holding the carpule wherein the carpule carrier has external threads on the proximal end; a syringe assembly having a syringe body containing a slidable needle assembly wherein the syringe assembly has external threads on the proximal end and wherein the syringe assembly is adapted for receiving the carpule carrier, and a plunger assembly adapted for coupling to both of said external threads and having a means for retracting the slidable needle assembly safely inside the syringe body after medication has been dispensed. 
     A method embodiment of a dental safety syringe for use with a carpule wherein the carpule has a proximal slidable seal and a distal seal comprises the steps of providing a carpule carrier for holding the carpule wherein the carpule carrier has threads on the proximal end, inserting the carpule into the carpule carrier, attaching a plunger assembly to the threads of a syringe assembly, inserting the distal end of the carpule carrier in a syringe assembly wherein the syringe assembly has syringe body and a needle assembly, pushing the needle assembly so that a needle fully extends outside the syringe body and is in a condition for delivering medication, attaching the plunger assembly to the syringe assembly, delivering medication to target tissue; and retracting the needle assembly inside the syringe such that an accidental needle stick is not possible. When the plunger assembly is detached from the combination of the carpule assembly and the syringe assembly, the plunger is available for reuse. The combination of the carpule assembly and syringe assembly, where syringe body securely contains retracted needle, is in condition for disposal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other, emphasis instead being placed upon clearly illustrating the principles of the invention. Furthermore, like reference numerals designate corresponding parts throughout several views. 
     FIG. 1 is illustrates the elements of an embodiment of a dental safety syringe showing the prominent features of each element in accordance with the present invention. 
     FIG. 2 illustrates a first step in assembling the components of FIG.  1 . 
     FIG. 3 illustrates a second step in assembling the components of FIG.  1 . 
     FIG. 4 illustrates a third step in assembling the components of FIG.  1 . 
     FIG. 5 illustrates a fourth step in assembling the components of FIG.  1 . 
     FIG. 6 illustrates a fifth step in assembling the components of FIG.  1 . 
     FIG.  7 . illustrates a sixth step in assembling the components of FIG.  1 . 
     FIG.  8 . illustrates a seventh step in assembling the components of FIG.  1 . 
     FIG.  9 . is a drawing of elements of a second embodiment of a dental syringe in accordance with the present invention. 
     FIG. 10 illustrates the elements of FIG. 9 partially assembled. 
     FIG. 11 illustrates a first step in assembling the components of FIG.  10 . 
     FIG. 12 illustrates a second step in assembling the components of FIG.  10 . 
     FIG. 13 illustrates a third step in assembling the components of FIG.  10 . 
     FIG. 14 illustrates a fourth step in assembling the components of FIG.  10 . 
     FIG. 15 illustrates a fifth step in assembling the components of FIG.  10 . 
     FIG.  16 . illustrates a sixth step in assembling the components of FIG.  10 . 
     FIG.  17 . illustrates a seventh step in assembling the components of FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The figures representing a safety syringe are shown as cross sections of components that comprise the present invention. Referring to FIG. 1, a syringe  100  is shown as three elements that will be assembled. The disassembled elements are shown to provide an understanding of the function of the safety dental syringe in accordance with the present invention and describe how the syringe would be used to injected medicine. A plunger assembly  110  is has a plunger shaft  4  with a thumb ring  1  on one end and a harpoon  3  on the other end. The harpoon  3  is attached to the plunger shaft after the shaft has been inserted through a hole in a threaded finger grip  2 . The end of the plunger shaft  110  having the thumb ring  1  is called the proximal end of the plunger assembly and the finger grip  2  end of the plunger shaft is called the distal end of the plunger shaft. The terms “proximal” and “distal” have the same meaning when referring to other elements of the safety syringe. Two sets of interior threads are on the inside of the distal end of the plunger assembly  110  and the threads are used to couple a carpule assembly  120  and a syringe assembly  130  as will be seen below. 
     The carpule assembly  120  has a carpule carrier  5  for holding a carpule  6 . The carpule  6  is a cylinder with seals at both ends to contain medication. A distal seal  7  on the distal end of the carpule will allow medicine to exit the carpule when the distal seal is pierced by a needle as will be seen. A slidable proximal seal  8  is initially located on the proximal end of the carpule. When medicine is forced out of the medication compartment  9  the slidable proximal seal is forced towards the distal end of the carpule  6 . The carpule  6  is a conventional or standard container for holding and dispensing medicine. As shown there is an opening at the distal end of the threaded carpule carrier for receiving the carpule. A wedge shaped ridge  121  that extends inwardly is located on the distal end of the carpule carrier. The ridge serves one element of a latch for coupling the carpule carrier to a groove in a needle carrier  13 . 
     A third part of the safety syringe is a syringe assembly  130 . The syringe assembly  130  has a threaded internal stop  10  inserted in the proximal end of a syringe body  11 . The threads of the internal stop will be coupled to one of the thread sets on the finger grip  2 . The distal end of the threaded internal stop, that is inserted inside the syringe body  11 , provide a stop for keeping a needle hub  13  from leaving the syringe body as will be seen in the discussion of FIG.  7 . The needle hub  13  has a needle  14  with a lumen going through the center of the hub and the needle is securely attached to the needle hub. The combination of the needle hub  13  and needle  14  are referred to as a needle assembly  12 . It should be noted that there is a notch  131  facing outward on the proximal end of the needle hub  13  and the notch serves as a second part of a snap latch that attaches the carpule carrier  120  to the needle hub. 
     FIGS. 2-8 illustrate steps for assembly and disassembly of the safety syringe of the present invention. It is helpful to note before discussing the steps that both the carpule assembly  120  and syringe assembly  130  are disposable, but that the plunger assembly  110  is reusable. 
     A first step (or operation  1 ) for the assembly of the safety syringe  100  is to attach the plunger assembly  110  to the carpule assembly  120 . FIG. 2 illustrates external (on the outside and at the proximal end) threads of the threaded carpule carrier  5  secured to the first set of interior threads of the threaded finger grip  2  where the first set of threads is the set having the smallest diameter. The first step is attaching carpule assembly  120  to the plunger assembly  110  by placing the proximal end of the carpule assembly inside the distal end of the plunger assembly  110  and screwing the units together until the carpule assembly and plunger assembly are firmly attached. Note that there is a space between the second set of threads (interior threads) of the threaded finger grip  2  and the outside of the proximal end of the carpule assembly  120 . 
     Referring now to FIG. 3 for a second step of assembly. The combination of the plunger assembly  110  and carpule carrier  120  is inserted in an opening on the proximal end of the syringe assembly  130 . The combination is pushed in the distal direction until the needle is completely extruded out of a tapered opening at the distal end of the syringe body  11  and the tapered end of the needle assembly  12  fits within the tapered opening of the syringe body. Next, step  3 , the syringe assembly is securely attached to the second set of threads on the plunger assembly  110 . After step  3  is completed both the syringe assembly  130  and the carpule assembly  120  are securely attached to the plunger assembly  110  as illustrated in FIG.  4 . Also during step  3  the proximal end of the needle  14  pierces the distal seal  7  of the carpule  6  so that medication may be delivered through the lumen of the needle. In addition when step  3  is completed the wedge shaped ridge  121  snaps into the groove  131  of the needle hub  13  thereby locking the distal end of the threaded carpule carrier  5  to the proximal end of needle assembly  12 . 
     Step  4 , illustrated in FIG. 5, is the step of pushing the harpoon  3  of the plunger assembly  110  into the proximal slidable seal  8  of the carpule. After the harpoon  3  is attached to the proximal slidable seal  8 , medicine is injected into target tissue by pushing the plunger shaft  4  in the distal direction using the thumb ring  1  and threaded finger grip  2 , step  5 . After the medicine is injected the disassembly steps begin. 
     As illustrated in step  6  of FIG. 7, the carpule assembly  120  is pulled, using the plunger assembly, in the proximal direction until the needle hub reaches the stop within the syringe assembly  130 . It should be noted that the needle assembly and carpule assembly are locked together with the wedge shaped ridge  121  and the groove  131 . As shown in FIG. 7, it is necessary to separate the syringe assembly  130  from the plunger assembly  110  by unscrewing the threaded finger grip  2  from the syringe assembly  130  before pulling the carpule assembly  120  in the proximal direction and towards the proximal end of the syringe body  11 . When step  6  is complete the needle  14  is completely inside the syringe body  11  and the syringe body now serves as a shield for protection from a needle stick. The final step of disassembly, step  7 , is detaching by unscrewing the plunger assembly  110  from the threads on the proximal end of the carpule assembly  120 . After step  7  is complete the syringe assembly  130  and the carpule assembly  120  are coupled together forming a disposable unit. Because force is required to move the needle assembly the needle is secured in the retracted position. The plunger assembly  110  is now available for reuse. 
     A second embodiment of the present invention is illustrated in FIG. 9 with the assembly and disassembly steps shown in FIGS. 10-17. For the second embodiment a modified finger grip  15  becomes part of the syringe assembly  130  and the threaded sleeve  16  replaces the finger grip  2  of the first embodiment. The syringe body  11  still serves as a shield as in the first embodiment and the ridge  121  and groove  131  are used to lock the carpule assembly  120  to the needle hub  13 . 
     FIG. 9 illustrates the three elements of the second embodiment of the dental safety syringe of the present invention. The carpule assembly of FIG. 9 has the threaded carpule carrier  5  and the carpule  6  as previously illustrated in FIG. 1. A modified syringe assembly  130  has the syringe body  11 , the needle assembly  12 , the threaded internal stop  10  but now has a threaded finger grip  15 . The plunger assembly  110  has the plunger shaft  4  with the harpoon  3 , the thumb ring  1  but now has a threaded sleeve  16 . The arrangement for assembly of the three elements  110 ,  120 , and  130  is illustrated in FIG.  10 . 
     FIGS. 10-17 illustrate steps for assembling and disassembling of the second embodiment of the present invention. FIG. 10 illustrates an alignment of the elements before assembly. First the carpule assembly  120  is attached to the plunger assembly  110  by screwing the units together, step  1  as illustrated in FIG.  11 . Next, step  2  the distal end of the carpule assembly  120  is inserted into the proximal end of the syringe assembly  130  as shown in FIG.  12 . After the carpule assembly  120  and needle assembly  12  are pushed forward, the threaded sleeve  16  is securely reversibly coupled the threaded finger grip  15  by locking tabs on the threaded sleeve  16  to a groove in the threaded finger grip, step  3 . A bayonet type coupling for step  3  would be understood by those skilled in the art. During step  3  the harpoon  3  is pierces and is attached to the proximal slidable seal  8  of the carpule  6  and the proximal end of the needle penetrates the distal seal making medication available for delivery. After medication is injected into target tissue, step  4  shown in FIG. 14 the disassembly steps begin. 
     To disassemble the threaded sleeve  16  with the bayonet type coupling is detached from the threaded finger grip  15  and the carpule assembly is pulled in the proximal direction, step  5  as shown in FIG.  15 . Next the proximal slidable seal is pulled in the proximal direction until the needle hub  13  reaches the stop in the syringe assembly  130  as shown in FIG. 16, step  6 . When the threaded sleeve is unscrewed from the external threads on the proximal end of the carpule assembly  120 , the plunger assembly  110  is separated from the combination of the carpule assembly  120  and the syringe assembly  130 . The above combination is disposable. The plunger assembly  110  is now ready for re-use. As in the first embodiment the syringe body serves as a shield from the needle. In addition the disposable elements for both embodiments are the syringe assembly  130  and the carpule assembly  120 . 
     All such modifications and variations of the embodiments of the dental safety syringe are intended to be included herein and are within the scope of this disclosure that is protected by the following claims.