I saw this viral video of a robotic arm made from cardboard and I had this urge to "inject" this idea into 3D printing. I was looking for a 3D model of an Injection but did not find any so I made this one. It is more a "placeholder" than a working "3D printable" object.
The idea is to scale this to your need and place into a hydraulic mechanism. I guess you would do the real life project from real injections anyway.