Method and plant for the thermal treatment of friction elements, in particular brake pads

A method for the thermal treatment of friction elements wherein friction elements are transported through a convective oven, the method comprising:

• i) arranging the friction elements in an orderly manner upon a plurality of trays, each tray having a perforated resting plate upon which a number of the friction elements are laid in a position next to one another in non-overlapping fashion;
• ii) stacking the plurality of trays on top of each other whilst being kept distanced from one another in a stacking direction by an amount that is greater than the thickness of the arranged friction elements in the same stacking direction, and forming groups of the stacked trays;
• iii) convectively heating the friction elements within a convective tunnel oven having a burner and a conveyor passing through it, in which the formed groups of the stacked trays having the arranged friction elements are placed side by side on the conveyor, such that by advancing the conveyor the arranged friction elements are transported through the convective tunnel oven in a direction (D1) of travel;
• wherein during the convective heating step the arranged friction elements are heated, by the burner, to a temperature of between 140° C. and 300° C., thus causing a controlled circulation of a flow (F) of burned gases, due to forced convection, within the convective tunnel oven;
• the flow (F) of burned gases being divided into a plurality of overlapping flows (F1-n;
• F2-m), said plurality of overlapping flows being opposite to one another and transversely directed in the direction of travel (D1), and
• in which the friction elements are arranged on the trays and then taken from the trays by means of at least one pair of manipulation robots having at least three numerically controlled axes of movement arranged as a first manipulation robot at a first end of the convective tunnel oven which has an inlet opening into the oven and a second manipulation robot at a second end of the convective tunnel oven, opposite to the first end which has an outlet opening from the convective tunnel oven;
• the trays being taken empty by the first manipulation robot at the first end, being deposited empty onto the conveyor, a first tray directly laid on the conveyor and subsequently filled by the first manipulation robot with a plurality of friction elements, and the subsequent trays piled on top of the first tray and filled with friction elements by the first manipulation robot one at a time to form a group of piled up trays;
• the friction elements being taken from the trays by the second manipulation robot at the second end, and the empty trays are removed from the conveyor one at a time by the second manipulation robot and arranged upon a belt conveyor, positioned externally below the convective tunnel oven, and by means of the belt conveyor the empty trays are carried back to the first end to be taken one at a time by the first manipulation robot.

A plant for the thermal treatment of formed friction elements, each of the formed friction elements comprising a block of friction material pressed onto a metal support the plant comprising:

• a tunnel convective oven presenting an inlet opening at a first end and an outlet opening at an opposing second end and a conveyor which passes through the tunnel convective oven, the conveyor having an extension in length that is greater than that of the tunnel convective oven, in order to have first and second opposite ends of the conveyor arranged externally to the convective tunnel oven, from which the conveyor emerges through inlet and outlet openings, respectively;
• a plurality of trays, each tray having a perforated resting plate designed such that a number of the formed friction elements can be laid directly onto the perforated resting plate in a position next to one another in overlapping fashion;
• the trays being designed to be piled on top of each other whilst being kept distanced from one another in a stacking direction by an amount that is greater than the thickness of the formed friction elements in the same stacking direction, each tray having a plurality of resting feet cantilevered from longitudinal sides of the tray, each of the resting feet comprising an upper end and an elongated bottom end, the upper end including a seat having an opening sized to receive the elongated bottom end of a vertically stacked tray;
• the conveyor being designed to be loaded, at its first end, with groups of piled up trays containing the formed friction elements and to carry in a direction of travel (D1) a plurality of groups of piled up trays arranged side by side through the tunnel convective oven beyond the outlet opening, at a controlled speed;
• wherein the tunnel convective oven comprises apparatus for sucking from the environment coupled to at least a burner, which are configured to generate within the tunnel convective oven a plurality of flows of overlapping burned gases (F1-n;
• F2-m);
• and combustion product suckers including at least a pair of extractors positioned at, or close to, the respective opposite ends of the tunnel convective oven;
• the overlapping flows of burned gases (F1-n;
• F2-m) being opposite to one another and transversely directed in the direction of travel (D1).