Machine assembly for conveying sheet-format substrates, comprising a first belt conveyor and a second belt conveyor, and a printing machine comprising said machine assembly

A machine assembly for conveying sheet-format substrates (01), comprising a first belt conveyor (02) and a second belt conveyor (03), these belt conveyors (02;

• 03) each having a continuously circulating transport belt (04;
• 06) and being arranged one after the other in the transport direction (T) of the substrates (01) conveyed on the respective transport belt (04;
• 06);
• the transport belt (04) of the first belt conveyor (02) and the transport belt (06) of the second belt conveyor (03) being arranged in the same transport plane extending rectilinearly in the transport direction (T) of the substrates (01);
• the transport belt (04) of the first belt conveyor (02) being diverted by at least 90° in relation to the transport plane at the rear end thereof, in the transport direction (T) of the substrates (01), at a diverting roller (16) and the transport belt (06) of the second belt conveyor (03) likewise being diverted by at least 90° in relation to the transport plane, in the same direction as the transport belt (04) of the first belt conveyor (02), at the forward end thereof, in the transport direction (T) of the substrates (01), at a diverting roller (17), which is arranged spaced a first distance (A) apart from the diverting roller (16) of the first belt conveyor (02);
• in a region between the diverting roller (16) of the first belt conveyor (02) and the diverting roller (17) of the second belt conveyor (03), the transport plane having a discontinuity point in the mechanical support of the substrates (01) to be transported;
• a guide device (18), which extends transversely to the transport direction (T) of the substrates (01) and guides the substrates (01) to be transported and comprises at least one lifting nozzle (19), being arranged in this region of the discontinuity point between the diverting roller (16) of the first belt conveyor (02) and the diverting roller (17) of the second belt conveyor (03);
• the guide device (18) comprising a tapered profile element (21), which extends transversely to the transport direction (T) of the substrates (01);
• the at least one lifting nozzle (19) of the guide device (18) being arranged so as to open into the tip (22) of the profile element (21);
• the tip (22) of this profile element (21) being oriented counter to the transport direction (T) of the substrates (01) toward the transport belt (04) of the first belt conveyor (02) and being arranged so as to be spaced apart by a first gap from the transport belt (04) that is diverted at the diverting roller (16) of the first belt conveyor (02);
• at least the transport belt (04) of the first belt conveyor (02) being designed as a suction belt that non-positively holds the relevant substrate (01) resting thereon with the bearing surface thereof;
• the suction force being achieved by a negative pressure that is set in relation to the ambient barometric air pressure by means of a suction device;
• the suction device implementing the suction force at the suction belt of the first belt conveyor (02) comprising at least one suction chamber (24);
• a wall (27) of a last suction chamber (26), in the transport direction (T) of the substrates (01), of the suction device being arranged spaced a second distance (B) apart from the diverting roller (16) of the first belt conveyor (02) in the transport direction (T) of the substrates (01) directly upstream from this diverting roller (16);
• the wall (27) of the last suction chamber (26) in the transport direction (T) of the substrates (01) and the outer cylindrical surface (28) of this diverting roller (16) of the first belt conveyor (02) being arranged so as to form a channel (29) through which air can flow;
• at least one counter-nozzle (31) being provided;
• the relevant counter-nozzle (31) being arranged so as to blow air into the channel (29), which is formed by the wall (27) of the last suction chamber (26) in the transport direction (T) of the substrates (01) and the outer cylindrical surface (28) of the diverting roller (16) of the first belt conveyor (02), in the direction of the suction belt;
• it being provided that the air that is blown into the channel (29) emerges in the transport direction (T) of the substrates (01) in front of a tangency point (32) that is formed by the suction belt at the diverting roller (16) of the first belt conveyor (02), through the suction belt, and pushing against a substrate (01) resting on the suction belt;
• an air current emerging from the at least one lifting nozzle (19) of the guide device (18) and the air current that is generated by the at least one counter-nozzle (31) in the channel (29) and that passes through the suction belt being oriented so as to come together above the tangency point (32) of the diverting roller (16) of the first belt conveyor (02);
• these two air currents forming a combined air current in an active region (W) that extends shorter than the diameter (D) of the diverting roller (16) of the first belt conveyor (02);
• and the combined air current being oriented so as to exert a pressure that acts against at least a part of the bearing surface of this substrate (01) between the suction belt and a substrate (01) to be transported thereon.