Patent ID: 7854720

Claim:
A needle-free injection device, comprising, a housing; a piston disposed at least partially within the housing, the piston having a forward end and a rearward end, the piston being configured to advance relative to the housing from a rearward-most position to a forward-most position during delivery of an injection, so as to cause injectable fluid to be expelled out through an injection orifice; a pressurized gas source configured to deliver pressurized gas to act upon the rearward end of the piston; a seal at the rearward end of the piston, the seal being configured to seal a variable-volume gas chamber defined within the housing between the rearward end of the piston and the pressurized gas source; and an impingement on an interior surface of the variable-volume gas chamber, wherein the impingement is configured to compromise the piston seal upon advancement of the piston to the forward-most position, so as to de-pressurize the variable-volume gas chamber after delivery of an injection.