The detection of forces acting on conveyor rollers of a laboratory device simulating the vertical section of a Sandwich Belt Conveyor

•Transport of bulk materials at angles of inclination, which considerably exceed the permissible angle of inclination of the transport of belt conveyors of a classic design.•Belt conveyor of a special design, the methodology of the laboratory measurement.•Measured horizontal compressive forces of bulk material acting on conveyor rollers.•The structural design of the pressing mechanism of the covering.•Measurement proposal, ultrasonic sensor S18UIA, force sensor U9C, strain gauge apparatus DS NET, DEWESoft X2 SP5 software. Using certain belt conveyors of a special design, it is possible to transport bulk material at angles of transport inclination significantly exceeding the permissible angle of inclination for traditional design. A special design of such a belt conveyor, described in this paper, uses the so-called cover belt to transport bulk materials at inclination angles from 20 to 90 degrees. By applying its weight or employing pressure, it exerts pressure on the surface of the layer of the transported material that is spread on the surface of the carrying belt. This paper aims to describe the laboratory measurement methodology and to detect the magnitude of the horizontal compressive forces of the transported bulk material acting on conveyor rollers (idlers). The article lists in the tables horizontal compressive forces obtained by measuring, which help to deduce the height of a bulk material column and its cross-section S2 [m2], defined by the width b [m] and height h [m] of the belts interspace. Knowledge of the magnitude of horizontal forces acting on conveyor rollers allows us to suitably design the stiffness of the compression coil spring in the pressing mechanism. It eliminates the undesirable shifts of working surfaces from the conveyor belts (carrying and covering), which prevents the flow of the transported material grains over the edges of the conveyor belts. One of the possible designs for the pressure mechanism is presented in this article. The article shows the values of the difference between the ratio of the measured compressive forces against the value of theoretically calculated stresses for different heights of the bulk material column and different heights of the interspace. For the maize material, the largest difference in the ratio of the measured compressive forces to the value of the theoretically calculated stresses was 78.1% and for river gravel, it was 71.6%.