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Reverse thread carpule dental safety syringe

  • US 5,330,440 A
  • Filed: 10/21/1992
  • Issued: 07/19/1994
  • Est. Priority Date: 10/21/1992
  • Status: Expired due to Term
First Claim
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1. A dental syringe and carpule combination comprising:

  • (a) a hollow elongated barrel having a first end and a second end;

    (b) a handle, spring and piston plunger combination, said plunger having a first end and a second end, the first end being adjacent the handle, said plunger reciprocating within the barrel, the handle slidably extending through the first end of the barrel, the second end of the plunger removed from the handle releasably engaging with a first end of a piston in the carpule;

    (c) a carpule receiving cavity in the barrel proximate to the second end of the barrel in alignment with the plunger;

    (d) threaded carpule head engagement means at the second end of the barrel opposite the handle and plunger for releasably engaging corresponding threads on a second end of a carpule;

    (e) a hollow liquid containing carpule having a piston end proximate to the second end of the plunger and a head end proximate to the second end of the barrel, the carpule having in a first interior end thereof a slidable piston which at a first end releasably engages with the second end of the plunger, and at a second opposite end releasably engages with the head end of the carpule, the head end of the carpule having threads for releasably engaging with the carpule head engagement means of the barrel, and threads on the carpule head for enabling a correspondingly threaded hub of a double pointed dental needle to be releasably affixed to an exterior end of the head;

    (f) a double pointed hollow needle and hub threadedly engaged with the threads on the head of the carpule, one end of the needle penetrating into the interior of the carpule and the other end extending from the end of the carpule head and the second end of the barrel, whereby when the piston is engaged and moved by the plunger in the direction of the carpule head and needle, liquid in the carpule is pumped through the hollow of the needle, and when the plunger and piston reach the end of the second head end of the carpule, the second end of the piston engages the carpule head so that when the handle, plunger and piston are rotated, the head and needle are threadedly disengaged from the second end of the barrel and when the handle, plunger and piston are moved in a direction away from the second end of the barrel, the carpule head and needle are withdrawn into the interior of the carpule.

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