Patent ID: 7740607

Claim:
A piston housing for use with an injection device, the piston housing comprising: a first module defining a first chamber and having a distal end and a proximal end, the first module having an orifice proximate the distal end of the first module, the orifice being in fluid communication with the first chamber; a second module defining a second chamber and having a distal end and a proximal end, the distal end of the second module being coupled to the proximal end of the first module, the second module having a first piston configured to couple to the injection device; a second piston positioned between the first and second chambers and having a first end and a second end; and a fluid bypass positioned between the first and second chambers and having a first end and a second end; wherein the fluid bypass is configured to fluidly couple the first and second chambers when the first and second ends of the second piston are between the first and second ends of the fluid bypass.