Banana screen, namely equal thickness screen, to shape and banana shape is similar to the name, the principle of screening in 1965 by France E Boerstlein first put forward the equal thickness screening method.
1 Working Principle
Here's how a banana screen works . Screen box seat type support on the spring, the use of directional excitation force generated by the shaker, so that the screen box for oblique reciprocating vibration.is the working principle diagram of the shaker. The two sets of eccentric blocks (M1 = M2) in the shaker operate in synchronous reverse motion. In each instantaneous position, the centrifugal force along the X-x direction of the component force always cancel each other, and along the Y-Y direction of the component force is always superimposed on each other, therefore, formed a single along the Y-Y direction of the exciting force, driving the screen box for reciprocating linear motion.
2. Determination of kinematic parameters
(1) the amplitude A
Usually, when used for banana screen, small amplitudes should be used. Linear vibrating screen amplitude A=4-6mm, here take A=5mm
Installation Angle α.
(2) Installation Angle α. Namely, the Angle between the screen surface and the horizontal plane. Screen hole for more than 50mlm linear screen inclination Angle of 5°~10°. banana screen for five sections, starting from the feeding end of 30°, 22.5°, 15°, 7.5°, 0°.
Mass ejection Angle beta.
(3) in the banana screen, the ejection Angle refers to the Angle between the vibration direction and the horizontal direction, and the ejection Angle β is 45°.
3. Calculation of kinetic parameters
Part of the technical parameters of banana screen: operating frequency: F =14HZ parameter vibration weight: M=15000kg. Screen surface area: S=18.6m2
3.1 Stiffness of vibration isolation spring K
K = M x ῳ n2 = M x 2 (ῳ / p)
Type: ῳ for work angular frequency of vibrating screen, ῳ = 840 PI / 30 = 87.92 rad/s;
P is the vibration frequency ratio, set P =5;
Then, according to the formula, K=4637955.84N/m
3.2 The vibration force required by the vibrating screen P
P = MA ῳ 2
Where: A is the shaker single Zhenfu, A=5mm.
Substitute into the formula, P= 579744.48n
3.3 Motor power required for shaker N
N = 1 ŋ / (N1 + N2)
Where: N1 is vibration power, kW; N2 is friction power, kW; ŋ is transmission power, ŋ=0.9~0.95.
Vibration power: N1=MA2n3c/1740 where: C is damping coefficient, C =0.2; N is the vibration frequency (rotational speed), n= 900R /min. In the formula, N1=31.4kW
Friction power N2= MAN3FD2/1740
Where: F is the friction coefficient of rolling bearing, f=0.003; D2 is the diameter of the journal, D2 =0.080m; If N2=7.5kW, N=1/0.95× (31.4+7.5)=41kW
4. banana screen finite element analysis
The finite element analysis software can be used for strength calculation, and the design quality can be greatly improved through continuous modification of the graph and repeated calculation.
4.1 Establishment of finite element model of banana screen
The shaker model was simplified, and the appropriate element types were selected in ANSYS, such as SHE1163 and Combine14 to establish the banana screen finite element analysis model, as shown in Figure 2.
2 Finite element analysis model of banana screen
4.2 Statics analysis of banana screen by ANSYS
Through static analysis, the stress concentration can be found, through repeated design modifications and software analysis, until the sieve box structure is optimal. [FIG. 3 is the stress distribution diagram of the sieve box of banana screen. The stress concentration is relatively concentrated at the position adjacent to the spring seat and the side plate. Since the vertical plate connected to the spring seat and the side plate and the patch plate on the inner wall of the side plate were removed during the simplification of the model, the stress concentration here can be neglected.
FIG. 3 Stress distribution diagram of sieve box
5 conclusion
The static analysis is carried out by ANSYS software, which provides a theoretical basis for the structural optimization of banana screen.
