Device for inflating a balloon

A balloon inflation device of the type comprising a syringe comprising a syringe body and a syringe piston slidably and rotatably displaceable in said syringe body, the piston presenting an outside thread over at least a fraction of its length, the device further comprising a retaining mechanism for retaining the piston and comprising, firstly at least one half-nut movable between a position where it is spaced apart from the thread, and in which the piston is free to slide in the syringe body, and a position where it engages the thread, in which free sliding of the piston is impossible, and in which the piston can be screwed into or out from the syringe body, and secondly, for each half-nut, a control member for controlling the displacement of the corresponding half-nut between its two positions, said member being movably mounted relative to the syringe body, wherein the retaining mechanism comprises, for each half-nut, at least one elastically-deformable element pressing against the corresponding half-nut and against the syringe body, and wherein the control member comprises a finger bearing against the corresponding half-nut and adapted, during displacement of the control member, to bear against two surfaces carried by the half-nut and offset from each other in a radial direction of the syringe body, the half-nut being in its position spaced apart from the thread when the finger bears against the surface that is radially closer to the syringe piston, and the half-nut being in its position engaged with the thread when the finger is pressed against the surface that is further away.