Needleless injector

Abstract

A needleless injector has a syringe body having an opening at one end, a piston housed within the syringe body for urging a liquid within the syringe body through the opening and a ram for driving the piston. A shock absorbing component is provided for reducing an initial transfer of force from the ram to the piston. The initial rate of pressure increase on the liquid is reduced, thereby controlling the rate of collapse of gas bubbles in the liquid.

1 - 18 . (canceled) 
     
     
         19 . A needle-free injector syringe, comprising:
 a piston housed within a syringe body;   a power source for applying an initial force to a ram to initiate delivery of a liquid and collapse of a bubble in the liquid;   wherein during a first stage of the delivery, a reduced force is applied by the ram to a piston thereby causing the bubble to collapse in a slow, controlled manner; and   further wherein during a subsequent stage of the delivery, the ram and piston are configured in the device so as to transfer substantially all energy of the ram to the piston.   
     
     
         20 . The needle-free injector syringe of  claim 19 , wherein the piston and ram are configured in the device so as to provide reduced force during the first stage by movement of the ram towards the piston causing compression of a closed volume of gas. 
     
     
         21 . The needle-free injector syringe of  claim 19 , further comprising:
 an additional component positioned between the ram and the piston which component is configured to cause an initial transfer of force from the ram to the piston which force is substantially smaller than a subsequent impact force between the ram and the piston.   
     
     
         22 . The needle-free injector syringe of  claim 21 , wherein the piston and ram are configured in the device so as to cause an initial transfer of force due to friction between the ram and the component causing a force to be applied to the piston. 
     
     
         23 . The needle-free injector syringe of  claim 22 , wherein the component is connected to the ram. 
     
     
         24 . The needle-free injector syringe of  claim 22 , wherein the component is connected to the piston. 
     
     
         25 . The needle-free injector syringe of  claim 22 , wherein piston movement causes formulation pressure to increase to from 1 to 6 Mpa. 
     
     
         26 . The needle-free injector syringe of  claim 21 , wherein the component comprises a cylinder, in which an end of the ram is slidably received. 
     
     
         27 . The needle-free injector syringe of  claim 26 , wherein the cylinder forms part of the piston. 
     
     
         28 . The needle-free injector syringe of  claim 27 , wherein the cylinder is closed at one end, the closed end lying adjacent the piston. 
     
     
         29 . The needle-free injector syringe of  claim 26 , wherein the cylinder is open at both ends. 
     
     
         30 . The needle-free injector syringe of  claim 26 , wherein the internal opening of the cylinder has a constant internal diameter. 
     
     
         31 . The needle-free injector syringe of  claim 30 , wherein the bubble present within the liquid collapses to about 1/20 or less of an original size. 
     
     
         32 . The needle-free injector syringe of  claim 31 , wherein the increase in pressure occurs within 200 μs. 
     
     
         33 . A needle free injector, comprising
 a piston housed within a syringe body;   a ram for driving the piston thereby causing liquid to be driven out of an exit opening of the syringe;   a component between the ram and the piston;   wherein the ram, piston, and component are configured such that;   during a first stage of the delivery, the component causes a reduced force to be applied to the piston; and   during a subsequent stage of the delivery, substantially any remaining energy of the ram is transferred to the piston.   
     
     
         34 . The needle free injector of  claim 33 , wherein the reduced force is a result of friction between the ram and the component. 
     
     
         35 . The needle free injector of  claim 34 , wherein the component is connected to an element chosen from the ram and the piston. 
     
     
         36 . The needle free injector of  claim 33 , wherein the reduced force moves the piston toward the exit opening. 
     
     
         37 . The needle free injector of  claim 36 , wherein the movement of the piston causes formulation pressure to increase to from 1 to 5 MPa. 
     
     
         38 . The needle free injector of  claim 37 , wherein the component comprises a cylinder, in which an end of the ram is slidably received. 
     
     
         39 . The needle free injector of  claim 38 , wherein the cylinder forms part of the piston. 
     
     
         40 . The needle free injector of  claim 39 , wherein the cylinder is closed at one end, and that closed and is positioned adjacent to the piston. 
     
     
         41 . The needle free injector of  claim 38 , wherein the cylinder is open at both ends. 
     
     
         42 . The needle free injector of  claim 41 , wherein the cylinder has a constant internal diameter. 
     
     
         43 . The needle free injector of  claim 42 , wherein the liquid formulation contains a bubble and pressure increase collapses the bubble to about 1/20 or less of its size prior to pressure being applied. 
     
     
         44 . The needle free injector of  claim 43 , where the pressure increase occurs within 200 μs. 
     
     
         45 . A needle free injector, comprising:
 a syringe body comprising an exit opening at one end;   a piston housed within the syringe body for urging a liquid within the syringe body through the exit opening;   a ram for driving the piston; and   a component positioned within the needle-free injector between the ram and the piston, the component configured to control an initial force applied to the liquid to be reduced thereby controlling bubble collapse speed immediately prior to extrusion of the liquid from the exit opening.   
     
     
         46 . The injector of  claim 45 , wherein the pressure in the syringe body increases to a pressure of about 1 to about 5 Mpa upon applying a force to the ram. 
     
     
         47 . The injector of  claim 46 , wherein pressure applied to the liquid collapses bubble size to 1/20 or less of its size prior to pressure being applied. 
     
     
         48 . The injector of  claim 47 , wherein pressure increase occurs within 200 μs. 
     
     
         49 . The injector of  claim 45 , wherein the component comprises a cylinder, in which an end of the ram is slidably received. 
     
     
         50 . The injector of  claim 49 , wherein the cylinder is open at both ends. 
     
     
         51 . The injector of  claim 50 , wherein the cylinder has a constant internal diameter. 
     
     
         52 . The injector of  claim 51 , wherein the cylinder has a length of between 1 mm and 5 mm.