Injection device

A pressure-operated injection device comprising:

• a housing,
• means to support in said housing an ampul having a plunger and a discharge opening,
• a ram slidably mounted in the housing coaxially with the supporting means for actuating said plunger,
• means to bias the ram to a retracted position,
• an accumulating chamber in said housing for accumulating gas,
• a source of gas under pressure,
• a first passage connecting the chamber and the ram,
• a first pressure actuated valve means controlling said first passage,
• said first valve means being spring biased to the closed position, opening responsive to a predetermined pressure and remaining open responsive to a pressure ranging from said predetermined pressure to a predetermined lower pressure,
• a second passage connecting the accumulating chamber to the source of gas under pressure,
• a second valve means controlling said second passage,
• means respeonsive to the opening movement of the first valve means to close the second valve means when the first valve means open and prevent further gas from entering the accumulating chamber, and
• a manually controlled valve in said second passage upstream of said second valve.

A pressure-operated injection device comprising a housing,

• means to support in said housing an ampul having a plunger and a discharge opening,
• a ram slidably mounted in the housing coaxially with the supporting means for actuating said plunger,
• means to bias the ram in a retracted position,
• a source of gas under pressure,
• said housing having a cylindrical cavity having a top wall, a bottom wall and a side wall, a gas accumulating chamber in the housing, a first passage connecting the chamber with the top of the cavity, a second passage connecting the source of gas with the chamber and third passage connecting the upper portion of the cavity with the ram,
• a piston in said cavity having an upper face facing the top of the cavity,
• a first valve member controlling the first passage, operatively connected to the upper face of the piston and having exposed to pressure in said first passage an upper face having a diameter smaller than the diameter of the piston,
• a second valve member to control said second passage operatively connected to the piston and movable to a position closing the second passage,
• resilient means to bias the piston upwardly to maintain the first valve member closed until a predetermined gas pressure is exerted on the upper face of the first valve member to initiate the downward movement of the piston and expose the piston to the gas pressure to accelerate the downward movement of the piston and the closure of the second valve member and prevent the return of the piston upwardly to close the first valve member until the gas pressure drops substantially below said predetermined pressure in order to supply gas under pressure to said ram to advance it and to provide for exhausting gas back through the first and third passage to the accumulating chamber on the retraction of the ram,
• means to connect said accumulating chamber to the atmosphere to exhaust gas therefrom as the ram retracts, and
• a normally closed manually controlled valve in said second passage upstream of said second valve member controlling the second passage.