Claims for Patent: 6,135,979

Summary for Patent: 6,135,979

Title:	Spring-powered dispensing device for medical purposes
Abstract:	A dispensing device, such as a needleless injector, comprising a spring, which provides an energy store, and a dispensing member movable, to effect a dispensing, under the force of the spring. A latch has a first position in which it restrains movement of the dispensing member and a second position in which it permits such movement. A trigger is operable by the user for moving the latch from the first position to the second position. A safety mechanism, preferably in the form of an appropriately shaped slot in the dispensing member, is effective before the device has been completely assembled to prevent movement of the latch to the second position.
Inventor(s):	Weston; Terence Edward (Eye, GB)
Assignee:	Weston Medical Limited (Eye, GB)
Application Number:	09/178,991
Patent Claims:	1. An injector for dispensing a liquid, which comprises a spring, which provides an energy store, a dispensing member movable, to effect dispensing, under the force of the spring, latch means having a first position in which it restrains movements of the dispensing member and a second position in which it permits such movement, trigger means operable by the user for causing the latch means to move from said first position to said second position, and a safety mechanism effective before the device has been completely assembled to prevent movement of the latch means to said second position, wherein the safety mechanism is provided by a slot extending into the dispensing member from an exterior surface thereof, the slot being defined in part by a pair of latch-engaging surfaces, the latch means having a safety position in which it cannot be caused to move to the said second position by operation of the trigger, in which it engages one of the surfaces, and engaging the other of the surfaces when in its said first position. 2. An injector according to claim 1, wherein the said one surface is substantially perpendicular to the intended direction of movement of the dispensing member, and the said other surface is inclined to the said direction of movement so that the movement of the dispensing member in the said direction exerts a force on the latch means, when the latch means is in its said first position, urging it towards its said second position. 3. An injector according to claim 1, having an outer casing surrounding the dispensing member and latch means, the outer casing having an aperture therethrough in the region of the latch means, the aperture providing access to permit insertion of a tool into the interior of the outer casing to move the latch means from its safety position to its said first position. 4. An injector according to claim 1, which is a needleless injector. 5. An injector according to claim 4, comprising a chamber containing a liquid to be injected and provided with an outlet orifice at one end thereof and a piston movable in the chamber to expel the said liquid through the outlet orifice, the dispensing member being spaced from the piston when the latch means is in its said first position and striking the piston to effect movement thereof when the latch means is moved to its said second position. 6. A device according to claim 1, wherein the spring is a gas spring. 7. A device according to any claim 1, wherein the spring is a mechanical spring. 8. A device for dispensing a material or article, which comprises a spring, which provides an energy store, a dispensing member movable, to effect dispensing, under the force of the spring, latch means having a first position in which it restrains movement of the dispensing member and a second position in which it permits such movement, trigger means operable by the user for causing the latch means to move from said first position to said second position, and a safety mechanism effective before the device has been completely assembled to prevent movement of the latch means to said second position, said safety mechanism being provided by said latch means having a safety position in which is cannot be caused to move to said second position by the operation of the trigger, and wherein the dispensing member has a pair of latch-engaging surfaces therein, the latch means engaging one of the surfaces when in its safety position, and the other of its surfaces when in said first position. 9. A device according to claim 8, wherein the dispensing member has a slot extending into it from an exterior surface thereof, the slot being defined in part by the said pair of surfaces. 10. A device according to claim 8, wherein the said one surface is substantially perpendicular to the intended direction of movement of the dispensing member, and the said other surface is inclined to the said direction of movement so that the movement of the dispensing member in the said direction exerts a force on the latch means, when the latch means is in its said first position, urging it towards its said second position. 11. A device for dispensing a material or article, which comprises a spring, which provides an energy store, a dispensing member movable, to effect dispensing, under the force of the spring, latch means having a first position in which it restrains movement of the dispensing member and a second position in which it permits such movement, trigger means operable by the user for causing the latch means to move from said first position to said second position, and a safety mechanism effective before the device has been completely assembled to prevent movement of the latch means to said second position, said safety mechanism being provided by said latch means having a safety position in which is cannot be caused to move to said second position by the operation of the trigger, and an outer casing surrounding the dispensing member and latch means, the outer casing having an aperture therethrough in the region of the latch means, the aperture providing access to permit insertion of a tool into the interior of the outer casing to move the latch means from its safety position to its said first position. 12. A device according to claim 8, which is in the form of a needleless injector. 13. A device for dispensing a material or article, which comprises a spring, which provides an energy store, a dispensing member movable, to effect dispensing, under the force of the spring, latch means having a first position in which it restrains movement of the dispensing member and a second position in which is permits such movement, trigger means operable by the user for causing the latch means to move from said first position to said second position, and a safety mechanism effective before the device has been completely assembled to prevent movement of the latch means to said second position, said device further comprising a chamber containing a liquid to be injected and provided with an outlet orifice at one end thereof and a piston movable in the chamber to expel the said liquid through the outlet orifice, the dispensing member being spaced from the piston when the latch means is in its first position and striking the piston to effect movement thereof when the latch means is moved to its second position. 14. A device according to claim 8, wherein the spring is a gas spring. 15. A device according to claim 8, wherein the spring is a mechanical spring.