fig1 a , b , c show three stages ( a — before starting , b — middle position and c — end position ) of a working needle - free syringe . referring to fig1 a , the fluid 4 medicine or vaccine ( or any other bioactive agent , e . g ., vitamins or minerals ) is contained in a container 1 made of plastic , glass or metal . the amount of the fluid accumulated in container 1 is determined by the position of piston or stopper or plunger 2 and flow regulator 3 , in this case a rubber washer through which the fluid will flow under sufficient pressure or , alternatively , by physically contacting or piercing washer 3 with a pointed or conical end of stopper 2 or similar device . container 1 may be filled with fluid , and then stopper 2 , which frictionally contacts the inner wall of container 1 , may be inserted to contain the fluid . thus , the end of stopper 2 that exerts pressure on the fluid 4 may be pointed , e . g ., conical , or flat depending on the volume of fluid to be injected and whether or not it is necessary to pierce . fig1 a shows the positions of the stopper 2 and washer 3 at rest . no external forces except for atmospheric pressure are exerted on stopper 2 . subsequently the pressure in the fluid beneath the piston is equal to the atmospheric , no expansion forces are applied to the washer 3 and the opening in washer 3 is closed . fig1 b shows the middle step of pressure fluid 4 where the elastic washes 3 is deformed but the pressure is still not enough to open the piercing of the elastic washer . fluid is released when the stoper &# 39 ; s motion deforms or expands washer 3 which is subjected to pressure equal to the pressure of the fluid inside container 1 . when the expansion of washer 3 reaches the critical level , a puncture orifice is formed in washer 3 and opens , and the fluid dose begins exiting the container . the velocity of the exiting fluid is determined by the pressure developed by the fluid provided the pressure exceeds the critical level to force the washer open so that the fluid can escape . the require minimal fluid velocity is primarily determined by the elasticity of the material and the thickness of the washer 3 . this feature assures additional stability of the washer position in the course of the fluid exit . fig2 a , b , c also show three stages ( a — before starting , b — middle position and c — end position ) of a working needle - free syringe , but the regulator of the pressure is located on the end of the container 1 . so the end of the container 1 is made from a sterile plastic material which works the same way as the elastic washer that is described in fig1 , or a microvalve is installed in the end of the body of the syringe which also opens under the required pressure . both the plastic end and the microvalve simultaneously function as nozzles . in fig3 a , 3b , and 3 c , a device utilizes two sources of energy to drive the piston 2 , 3 and stopper 9 . fig3 a , b , c ( a — start position , b — energy of the spring and compressed gas release to drive the piston forward to apply pressure to the medicine , c — mechanism to return the energy to the start position ). the syringe in this case actually contains the pistons : solid or hollow piston 3 which contacts the inside of hollow piston 2 , which partially covers piston 3 , which impacts piston ( stopper ) 9 . a chamber 11 is formed between piston 3 and the inner wall of piston 2 and contains compressed gas . a spring 14 is provided to force piston 2 and piston 3 in a direction toward stopper 9 to compress the fluid . a spring 16 holds spring 14 in place by retention in button 15 of piston housing 1 . actuating mechanism 13 is provided to hold spring 14 , piston 2 and piston 3 in start position until desired for use , and when activated by pushing the button 15 which pushes the lever 12 so that it no longer holds the pistons 2 , 3 and the energy of spring 14 is released to drive the piston 2 with the piston 3 forward without releasing gas pressure yet . compressed gas is provided in chamber 11 to further provide force on the piston 3 to eject the fluid before there is a substantial drop in the energy being exerted on stopper 9 by piston 3 . a retaining mechanism 4 having a lip is provided on the lateral portion of piston 2 to hold piston 3 in a position by contact with a receiving slot in the piston 3 so that the gas in chamber 11 remains compressed until the retaining mechanism is released once the piston reaches the piston shown in fig3 b . the retaining mechanism is released once because it is spring - like and it moves outward into receiving slots 5 of the inner wall of the housing , thereby allowing the compressed gas to exert force on the piston 3 propelling it further against the stopper 9 . this dual - energy providing system allows a fairly rapid and continuous pressure to be exerted so that the fluid 8 is ejected at a substantially uniform pressure and velocity through the nozzle mechanism which is shown and described in fig1 and fig2 . thus , unlike with prior art devices , there is no or insubstantial slowing of fluid velocity toward the end of the spring or gas action because a second energy force replaces energy lost by the spring as it uncoils . in operation , the pressure exerted on stopper 9 as well as the pressure exerted by the piston 2 on the fluid located beneath the piston increases . the stopper 9 with seal 10 is moved downward toward exit end of container 7 by force , e . g ., by a spring and compressed air , or other means . fig3 c shows the mechanism to return the energy to the start position . instead of the container 7 , the cylinder 17 is threaded onto the housing 1 . the screw 18 , rotated by lever 19 , moves the piston 3 , piston 2 and spring 14 back to the start position and simultaneously compresses the gas in chamber 11 . fig4 shows a system that has three types of energy . two types of energy and the mechanism to start them are the same as the system in fig3 . however , a ball 20 is fit in a hollow piston 3 , which provides a third type of additional energy . ball 20 is retained by ball holder 21 in the pre - injection position . when the device is activated , holder 21 releases ball 20 , which provides additional force via inertia to drive piston 3 forward to deliver the dose of fluid . the ball may be used in conjunction with the spring and compressed gas , or may be used in conjunction with either of those . the exit section of the device may simultaneously contain more than one exit port with regulators of pressure working as nozzles . the exit section of the syringe that contacts the skin is made from soft elastic material for reducing the impact effect of the inertia the pistons .
the present invention relates to a needle - free syringe which has a closer that can be released or otherwise opened such that a greater percentage , and preferably all of the desired dose of fluid vaccine or other active agent is injected at a substantially uniform velocity . the dose is delivered by applying sufficient pressure to the fluid , which is stored in a suitable container , to push it toward a pressure - releasable closure such that the desired dose or volume of fluid is ejected from the device to the appropriate layer of the body .