In mineral extraction, particularly in underground mining, scraper chain conveyors, which can be configured as single scraper chain or double scraper chain conveyors, are used. Scraper chain conveyors of the generic type are used, in particular, as face conveyors, in which, over large face lengths, the mined material has to be continuously evacuated with the scrapers fastened to the revolving scraper chain and transferred onto further conveying devices, such as drift conveyors, which can also consist of belt conveyors. A scraper chain conveyor generally has at both its ends a chain drive, with which the endless scraper chain revolving in the upper strand and lower strand is driven with the scrapers which are connected thereto.
A scraper for a so-called double-middle scraper chain conveyor, having a scraper web, a chain attachment region and scraper wings formed integrally onto the scraper web is known from DE 102 25 341 C1, to which is incorporated by reference herein in supplementation of the present disclosure.
In the prior art, ambitions to minimize the forces which shall be transmitted from the respective drives into the revolving scraper chain, in order to be able to reduce the capacities installed at the drives or, with the same capacity, transport higher quantities with the same scraper chain, have long existed. In EP 1 276 685 B1, it is proposed to this effect to make the scraper chain and/or the scrapers consist at least partially of a plastic which is self-extinguishing, flame-retardant and has anti-static properties, together with high mechanical strength. Through the use of plastic as the material for making the scraper chain and/or the scraper, a reduction in the weight of the scraper is intended to be achieved, whereby the drive capacity to be installed can be designed smaller or a larger conveying volume can be handled. According to one illustrative embodiment of EP 1 276 685 B1, the scraper is intended to consist of a metallic sheath, the interior of which is filled with a plastic and, according to another illustrative embodiment, the scraper is intended to be made fully of a suitable plastic, where possible the scraper chain also.
From WO 2004/048234 A1 it is known to make the entire scraper of plastic, the plastics scraper being intended to be connected to the metal chain links of a metallic scraper chain. In order to achieve a close attachment between scraper and chain, the fully plastics scraper is intended to be cast directly onto the chain links of the scraper chain. A drawback with this is that the connection can only be established above ground, so that the entire scraper chain would have to be brought from below ground to above ground in order to exchange such scrapers. An exchange of individual scrapers in the installed state of the scraper chain in the scraper chain conveyor is impossible.
DE 23 53 005 A1 discloses scrapers for a single-chain conveyor, in which a link of the simple chain is inserted between the top web and the top side of a chain clamp in order to connect the scraper to the simple chain. In order to reduce noise and wear, the sliding surface of the scraper consists of plastic. To this effect, the bottom side of the chain clamp can be coated with a plastics sliding surface, or it is provided with a plastics moulding which is anchored in a dovetailed transverse groove running transversely to the motional direction. In addition, the scraper wing ends can consist of exchangeable plastics caps, which are respectively fastened to a holding portion on the top web by means of a clamping sleeve. The plastics caps are provided on their bottom side with slide beads.
For double-middle scraper chain conveyors, it is known from WO 2004/065270 to have the top web and the chain clamp consist of different materials in order to minimize the weight of the scraper. As materials for the top part, plastic, aluminium or ceramics are proposed in order to obtain a top part which is as lightweight as possible. The scraper ends can also consist of end caps, which are movably fastened to the top part by means of clamping sleeves and a tongue and groove connection, for which holding portions are configured on the top web, which holding portions form the tongue and engage in a horizontal groove on the inner sides of the end caps.