A fluid delivery device for delivering a substance to a patient with a steeply decreasing supply flow rate, comprising: at least first and second deposits (29, 31)； at least first and second springs (35, 37) that are located adjacent to said first and second deposits (29, 31) respectively； at least one infusion device (13)； a fluidic communication path that includes said first and second deposits (29, 31) and said at least one infusion device (13)； and at least one flow limiter in said fluidic communication path； characterized in that said springs have at least an intermediate range (M) of operation, said springs having two different spring forces that are applied to the reservoir system, wherein: said first and second reservoirs (29, 31) provide a flow of fluid with a substantially constant first flow when said first spring (35) is in said first intermediate operating range (M)； and said first and second reservoirs (29, 31) provide a fluid flow with a second substantially constant flow rate when said second spring (37) is in said second intermediate operating interval (M), wherein said second flow rate is less than said First flowUn dispositivo de suministro de fluido para suministrar una sustancia a un paciente con un caudal de suministro escalonadamente decreciente, que comprende: al menos primer y segundo depósitos (29, 31)； al menos primer y segundo resortes (35, 37) que están situados adyacentes a dichos primer y segundo depósitos (29, 31) respectivamente； al menos un dispositivo (13) de infusión； un camino de comunicación fluídica que incluye dichos primer y segundo depósitos (29, 31) y dicho al menos un dispositivo (13) de infusión； y al menos un limitador de flujo en dicho camino de comunicación fluídica； caracterizado por que dichos resortes tienen al menos un intervalo intermedio (M) de funcionamiento, teniendo dichos resortes dos fuerzas de resorte diferentes que son aplicadas al sistema de depósito, en donde: dichos primer y segundo depósitos (29, 31) p
