Portable device for delivering medicaments and the like

A portable device for delivering a medicament or the like into the body of a human or animal subject, the device comprising:

• a medicament compartment containing the medicament or the like to be delivered;
• delivery means comprising an orifice through which the medicament or the like is expelled from the device;
• an internal combustion engine which provides the motive force by which the medicament is expelled from the device;
• a body comprising a cylinder, a piston located within the cylinder, and a cylinder head;
• a fuel reservoir, said reservoir comprising sufficient fuel to power a plurality of combustion cycles of the engine;
• a fuel inlet to admit fuel from the reservoir into the engine, and further comprising
• (i) means for causing compression of the fuel/combustion-supporting gas mixture within the combustion chamber;
• (ii) restraining means which serves to keep the piston in place against the pressure of the compressed fuel/combustion-supporting gas mixture, but which is insufficient to restrain the piston when the mixture is ignited;
• and
• (iii) a weak return means which is only just sufficient to overcome the inherent resistance of the piston when the device has been fired.