A milking robot (1) for the fully automatic milking of dairy animals comprises at least one moving component (2, 9) and a cylinder (4) configured to support a movement of the component, which cylinder has a cylinder wall (11) having an aeration opening (8), as well as a cylinder rod (5) slidable into and out of the cylinder, wherein the cylinder wall surrounds at least one variable volume part (13), which volume part is free from pressure fluid connections for displacement of the cylinder rod and, furthermore, is configured to remain, via said opening, substantially in pressure equilibrium with an environment of the cylinder, wherein to the cylinder wall around said aeration opening is connected a gas collecting device (7), which has a changeable volume and which, together with the variable volume part, forms an airtight gas volume, wherein the gas collecting device has a minimum volume greater than zero. It is thus possible to keep the variable volume part at substantially ambient pressure, so that, upon retraction and extension of the cylinder rod, no unnecessary counterpressure is created in the cylinder, thereby making the, working more reliable. At the same time, even in the event of a leak in the gas volume, less or no exchange of gas, dirt and the like with the environment will take place, at least not via packings and the like, so that the cylinder acquires a better service life and reliability.L'invention concerne un robot de traite (1) pour la traite entièrement automatique d'animaux laitiers, comprenant au moins un élément mobile (2, 9) et un cylindre (4) conçu pour soutenir un mouvement de l'élément, ledit cylindre a une paroi de cylindre (11) ayant une ouverture d'aération (8), ainsi qu'une tige de cylindre (5) pouvant coulisser dans le cylindre et hors de ce dernier, la paroi de cylindre entourant au moins une partie de volume variable (13), ladite partie de volume étant exempte de liaisons de fluide sous pression pour le déplacement de la tige de cyli
