The present invention relates to a device for expelling a predeterminedquantity of medicament comprising drivingmeans comprising an energy- accumulating member, a nut, and a driver fordriving a pressure means and activation means foractivating said driving means wherein said pressure means comprises a movablewall part arranged inside a 2container and a threadedplunger rod arranged to interact with said driving means for pushing saidmovable wall part forwardly, and wherein said activationmeans comprises a manually operated push button arranged on the front end ofthe device for promoting an ergonomic handling ofthe device and wherein said activation means are capable of interacting withsaid driving means in a stepwise mode such that eachtime said push button is depressed said pressure means moves an step exertingpressure on the medicament inside the container andexpelling a predetermined quantity of the medicament through the opening.
