TH10462B - Syringe - Google Patents

Abstract

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Claims (13)

1. A syringe consists of a tubular body, one end closed and the other open; a piston rod, which can be accommodated within the body to create a variable volume chamber; and a needle shackle, which is designed to support and hold a hollow needle. This shackle is supported by or within the wall of the body and can move significantly in a direction parallel to the main axis of the body between two positions: a first position where the needle extends from one end of the body and its interior contacts the chamber, and a second position where the outer end of the needle is retracted. The shackle has extensions that selectively engage with the wall of the body at the first and second positions to maintain its position, and can also be supported through the wall of the body at the second position to engage the piston rod, preventing axial movement of both the shackle and the piston rod relative to the body. 2. A syringe as claimed in claim 1, whereby the needle holder is able to rotate around an axis significantly parallel to its direction of motion, and such projection extends radially from the needle holder, whereby the rotation of the needle holder causes such projection to pass through the wall of the barrel and engage with the piston rod. 3. A syringe as claimed in claim 1 or claim 2, whereby the needle holder can be supported in a tube provided on or in the wall of the barrel and can move along the tube to allow movement between the first and second positions. 4. A syringe as entitled in claim 3, with a longitudinal groove formed to accommodate a sliding protrusion. 5. A syringe as claimed in claim 4, where grooves are formed with transverse projections at positions corresponding to the positions of both the first and second projections, where rotation of the needle support causes these projections to engage with the corresponding grooves when in the first and second positions. 6. A syringe as claimed in claim 5, where a hole is provided in the wall adjacent to the transverse groove at the second position to allow the projection to pass through the wall in order to engage the piston rod. 7. A syringe as claimed in claim 6, where the hole is made to the required size, flexible deformation of the protrusion and/or edge of the hole to allow the protrusion to pass through the wall. 8. A syringe as claimed under any of the preceding claims, whereby the piston rod shall be formed with a radially curved surface along its length which shall engage with the protrusion when engaged to prevent such axial movement of the piston rod. 9. A syringe as claimed in claim 8, where the curved surface is positioned in such a way that when the piston rod is fully supported within the barrel, the curved surface can be engaged by another part. 10. A syringe as claimed in claim 8 or claim 9, where multiple curved surfaces are provided along the length of the piston rod. 11. A syringe as claimed under claim 8, claim 9, or claim 10, where the curved surface is provided with an indentation on the side of the piston rod. 12. A syringe as claimed under any one of Claims 8, 9, or 10, where such curved surface is formed by radially protruding edges provided along the length of the piston rod. 13. A syringe as claimed under any of the preceding claims, whereby such projection includes an extension which can be supported through the wall of the barrel and can be attached to the piston rod.