Abstract: The invention relates to a protective structure associated with a work unit. The protective structure includes a mobile portion having movement in two senses according to a straight direction. The protective structure also includes two rotatable support elements idle about respective mutually parallel axes which are normal to the straight direction and which are internally supported by box structures connected to the mobile portion and which are arranged on opposite sides with respect to the mobile portion with reference to the straight direction. The protective structure further includes two blinds, respectively windable about the support elements and having a first end connected to the support element and a second end connected to a fixed structure on which a kinematic connector for the support element is supported.