Needle free hypodermic injector and ampule for intradermal, subcutaneous and intramuscular injection

A needle free hypodermic injector comprising an injector assembly and at least one medicament containing ampule removably attachable to said injector assembly, said injector assembly comprising an elongated hand manipulatable housing, said housing comprising:

• a main body portion containing a mechanical impact impulse means comprising a drive rod linearly reciprocatable within said housing between a cocked position and an injection position, a compressible drive spring linearly concentric about a rear portion of said drive rod, said spring being confined between a stationary abutment within said housing and a projection substantially midway along said drive rod whereby rearward displacement of said drive rod compresses said spring, a latch mechanism cooperating with said projection to releasably hold said drive rod in a cocked position wherein said spring is compressed, a release means to release said latch mechanism when injection is desired, and a cocking means cooperating with said drive rod and operable to draw said drive rod in a rearward direction to said cocked position thereby compressing said spring and engaging said latch mechanism;
• a forward nose portion adapted to removably receive said at least one ampule and having detent means to releasably secure said ampule to said injector assembly when said impact impulse mechanism is in said cocked position, said at least one ampule comprising a body having a forward end and a rearward end, a substantially planar upper surface and a stepped lower surface having a forward facing step face therein, said body having formed therein behind said step face a horizontally disposed substantially cylindrical medicament chamber open at said rearward end and narrowing to at least one jet orifice in said step face, said chamber being sized and positioned to receive a forward end of said drive rod when said ampule is secured to said injector assembly and said latch mechanism is released, said chamber further containing a sealing plunger providing a means to retain medicament in said chamber, said plunger adapted to be engaged by said drive rod upon release of said latch mechanism, whereby said drive rod drives said plunger forward within said chamber forcing said medicament under pressure through said jet orifice for injection into a skin surface held against said ampule.