Dissipateur visqueux

A dashpot, also known as a damper, is a mechanical device that resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly used in conjunction with a spring. The process and instrumentation diagram (P&ID) symbol for a dashpot is . The two most common types of dashpots are linear and rotary. Linear dashpots — or linear dampers — are used to exert a force opposite to a translation movement. They are generally specified by stroke (amount of linear displacement) and damping coefficient (force per velocity). Similarly, rotary dampers will tend to oppose any torque applied to them, in an amount proportional to their rotational speed. Their damping coefficients will usually be specified by torque per angular velocity. One can distinguish two kinds of viscous rotary dashpots: Vane dashpots which have a limited angular range but provide a significant damping torque. The damping force is the result of one or multiple vanes moving through a viscous fluid and letting it flow via calibrated openings. Continuous rotation dashpots which aren't limited in their rotation angle but provide a smaller damping coefficient. These use the friction generated by the shearing forces induced in the viscous fluid itself by the difference in motion between the dashpot's rotor and stator. A less common type of dashpot is an eddy current damper, which uses a large magnet inside a tube constructed of a non-magnetic but conducting material (such as aluminium or copper). Like a common viscous damper, the eddy current damper produces a resistive force proportional to velocity. A common use of the eddy current damper is in balance scales. This is a frictionless method that allows the scale to quickly come to rest. Dashpots frequently use a one-way mechanical bypass to permit fast unrestricted motion in one direction and slow motion using the dashpot in the opposite direction.