Natural escapement for horological movement and horological movement comprising such an escapement

A natural escapement for horological movement carrying out a succession of operating cycles each comprising a first and of a second alternation of a balance during which the balance moves from a first extreme position to a second extreme position by passing through a middle rest position, then from its second extreme position to its first extreme position by passing again a second time through its middle rest position, said balance comprising a balance wheel on an arbor of which is adjusted a balance plate, said natural escapement comprising a first escape wheel set having at least one first toothing, said first escape wheel set, arranged to be driven by a wheel set of the train of the horological movement, driving in turn a second escape wheel set having at least one second toothing, the first and second escape wheel sets forming a kinematic chain arranged to cooperate with an anchor capable of pivoting about an anchor-staff, the balance plate causing the anchor to pivot with each of the first and second alternations, said anchor being arranged to lock respectively the first and the second escape wheel set temporarily during the second and first alternations of an operating cycle, the anchor further comprising a first, respectively a second safety lever, these first and second safety levers being arranged so that, in the absence of the balance, one or other of the second and first escape wheel sets, by driving the second or the first safety lever, causes the anchor to pivot to ensure the locking of the first or of the second escape wheel set by abutment of this said first or of this said second escape wheel set on a portion of the anchor that ensures the function of a stop pallet-stone of said first or of said second escape wheel set during normal operation of the escapement, the first and second safety levers being arranged so as not to be in contact with the first and second escape wheel sets during normal operation of the escapement during which it is the balance plate that causes the anchor to pivot.