Abstract: A dispenser for viscous materials has a housing with a moveable wall that divides the interior volume of the housing into a distal product chamber and a proximal pressure chamber. An outlet from the product chamber is located adjacent to the distal end of the housing and an air inlet is provided to allow air to enter the pressure chamber. Displacement of the product occurs when accumulated excess air pressure in the pressure chamber acts on the back of the movable wall. The excess air pressure is built up by a bellows assembly arranged in fluid communication with the pressure chamber. On actuation, the bellows can be reduced in volume and subsequently recover by entry of air through the inlet. The direction of force application is preferably perpendicular to the housing axis and the location of the bellows is preferably distant from the product outlet.

Abstract: A dispenser for viscous materials has a housing with a moveable wall that divides the interior volume of the housing into a distal product chamber and a proximal pressure chamber. An outlet from the product chamber is located adjacent to the distal end of the housing and an air inlet is provided to allow air to enter the pressure chamber. Displacement of the product occurs when accumulated excess air pressure in the pressure chamber acts on the back of the movable wall. The excess air pressure is built up by a bellows assembly arranged in fluid communication with the pressure chamber. On actuation, the bellows can be reduced in volume and subsequently recover by entry of air through the inlet. The direction of force application is preferably perpendicular to the housing axis and the location of the bellows is preferably distant from the product outlet.