Improve design and analysis on transitional chute of scraper conveyor
Shuping Wang 1,a and Zhaojian Yang 1,b
1College of Mechanical Engineering, Taiyuan University of Technology, Taiyuan 030024 China
a sp311@tom,
b yangzhaojian@tyut.edu
Keywords：Scraper conveyor, Transitional chute, Improve design, Wear
Abstract. To avoid the corrosion of transitional chute of scraper conveyor, optimization is needed on the structural of transitional chutes. After analyzing the force on turning point of transitional chute, multi-body dynamic experiments were made. The results show that, the improve design decrease the force on the turning point obviously and there are no extra difficulty on manufacture and installation. The experiment and analysis can conclude that the forces, which influence the wear of transitional chute, are depended on the transition arc radius but not transitional angle. Introduction
Scraper conveyor is one of the important equipment on the modern fully-mechanized coal mining. Acco
rding to the demand of coal transportation, Scraper conveyor’s two sides (head and tail) are higher than the middle and the transitional chutes are the joining parts for the middle through to the tail or head. [1] As a slot of the scraper conveyor, transitional chutes showed the entire slot’s character, including wear. [2] But, the wear of transitional chute is more serious on the turning point than other slots. Seriously, deep groove was ploughed by the round chain on the turning point. By analyzing the transitional chute service condition and the calculator the contact force between rollers chain with middle plate, the paper seek the ways to reduce wear without extra difficulty on manufacture and installation.
Transitional chute and the problem
Transitional chute. Transitional chute is assembled in the scraper conveyor in Fig.1. As the figure shows, ‘h’ is lifting height; ‘α’ is transitional angle and the ‘is speed of chain. For the transitional angle, every section is unique in structure and installation position is fixed. Fewer transitional chutes are needed if the transitional angle bigger. So, bigger transitional angle is benefit to reducing the consumption on manufacture and installation.
Problems. In production progress, deep Array
grooves can be found at the point A in the
Even more, the middle plate will be wear
away. At the same time, it was founded that
transitional angle and the angle bigger the
wear more serious. A small transitional
angle α is benefit to reducing the slot’s
wear, but, a small transitional angel needs
more section for transitional chutes. So, there is a contradiction between wear and manufacture with installation. At present, producers use middle α to solving the problem. But, it’s difficult to solving the conflict.
Wear
The wear of middle plate is the key problem for scraper conveyor; translate speed, working condition
and material matching influence the wear at different degree. [1]. Transitional chute had all kinds wear which other slot has, and the wear on turning point A （showed in fig.1）is more serious. The reason for the serious wear is the normal force is bigger than others, so, analysis on contact force between chain and middle plate is the key to solve the problem.
Force. Fig 1 shows assemble of the chain and transitional chute and the fig.2 shows the vertical ring 2‘s forces. As it shows, vertical ring 2 is pulled by level ring 1 with F 1 along the direction of chain velocity, at the same time, the ring 2 is drew with F 2 by plate ring 3, the direction is showed in fig 3. For the reason that, the F 1 is a little bigger than F 2, here, consider F 1 is equal to F 2 for convenience of analysis. And then, the force on vertical ring 2 by turning point of transitional chute is F ,
.                                              (1)
So, normal force on the turning point A by vertical ring 2 is calculated by the first function.
F 11 and level ring 3 is useful to decrease the force ’F ’,
which is benefit to reduce the wear of transitional chute
by vertical ring. We can found that, a big curvature
radius arc is benefit to decrease the angle between the
two level rings. Fig.3 shows the transitional curve. In
fig.3, ‘γ’ is used to indicate the angle between level ring
1 and level ring 3 to different from transitional angel ‘a’.
So, the angle between _
OC (point C is belong to level
ring 3 and point O is the center of circle) and _OB  (point B is belong to level ring 1) is the same as ‘γ’.
Then,
R+2d=p/2sin(γ/4)                                                            (2) Here, ’d’ is the diameter of ring
So,
R ≥p/2sin(γ/4)                                                              (3) That is to say, larger ‘R ‘and little ‘γ’, the force on turning point is more little. And the magnitude
of the force is 。 7 3000
6 365 0.104 F 1 14.75%
7 5000
3.5 609.4 0.061F 1 50% 15 3000
6 776.46 0.104 F 1 60.1%
15 5000    3.5 1294.1 0.061F 1 76.7%
Table 1 says ，when the transitional angle is 7°，curvature radius of transitional arc is 3000mm, the decrease amplitude of the force on turning point is 14.75%，and the length of arc only 365mm. If the curvature radius of transitional arc is 5000mm, decrease amplitude of the force on turning point is 50% and only 609.4mm transitional chute needed to be arc. When the transitional angle is 15°，the improving design will decrease the force more clearly.
Calculation result and analysis
To verify the result of improve design, simulation experiment was held with ADAMS[3]. In the experiment, contacting forces between chain and middle plate were detected, and if the chain was on the turning point, the contacting force reached the maximum. In the test, transitional angle was 7 and 15°, curvature radius of transitional arc was 3000mm and 5000mm 。
Influence of pre-tightening force. Foregoing analysis prove that, the force on turning point is proportional to the tension of the chain F 1, F 1 is directly related to the pre-tightening force. So, the forces on turning point are larger with pre-tightening force bigger. Fig.5 is the relationship between the contacting force with time when the transitional angle is 7°,curvature radius of transitional arc is 3000mm. Fig a is the relationship when pre-tightening force is 2000 N. but Fig b is when pre-tightening force is 1000N. Fig 5-a shows that, the maximal connecting force is up to
Fig. 4  Calculation model  Transitional chute
Transitional arc
Chain
1850~2100N, but when the pre-tightening is 1KN, the force is 1200~1400kN (as the fig. 5-b shows). The force on turning point is higher with pre-tightening force, but is not proportional to pre-tightening force.
Contacting force on turning point Contacting force on turning point
a)  Pre-tightening force is 2000N                b)  Pre-tightening force is 1000N
Fig. 5 Relationship between contacting forces with time in different pre-tightening force
Influence of velocity. Fig 6 is the relationship between the contacting forces with time when the transitional angle is 7°, curvature radius of transitional arc is 5000mm and the pre-tightening force is 1kN. Fig a is the relationship when chain speed is 1m/s and fig. b is the relationship when chain speed is 2m/s. Fig.6 shows that when the chain speed is 2m/s, the maximal connecting force is 0.6~1.1KN，and chain speed is 1m/s，the maximal connecting force is 0.6~1.3KN. Obviously, connecting force on turning point is lower with the speed higher.
Contacting force on turning point Contacting force on turning point
a) Chain speed is 2m/s b) Chain speed is 1m/s
Fig.6 Relationship between contacting forces with time in different velocity Same transitional angle with different transitional arc. Fig 7 is the relationship between connecting forces with time when the transitional angle is 7°and other condition is equal but curvature radius of transitional arc. Fig a is relationship between connecting force with time when the curvature radius of transitional arc is 3m, but fig b is 5m.As the fig 7 shows, when the curvature radius is 3m, the connecting force on turning point is 1500N~1800N，but when the curvature radius is 5m, the mean connecting force on turning point is 800N~1100N. This is decreased by 46.7% than the force with 3m curvature radius. And the result was consistent with the calculation result in table 1.
scraperSame transitional arc with different transitional angle. Fig 8 is the relationship between connecting forces with time when curvature radius of transitional arc is 5m and other condition is equal but transitional angle is different. 7°fig. a is the relationship when the transitional angle is 7°and fig b is the relationship when the transitional angle is 15°fig8 shows that  the mean
a)Curvature radius of transitional arc is 3m        b) Curvature radius of transitional arc is 5m
Fig 7 Relationship between contacting forces with time
curvature radius of transitional arc
a)Transitional angle is 7°              b)  Transitional angle is 15°
Fig 8 Relationship between connecting forces with time in the same curvature radius of transitional arc
but different transitional angle
Summary
Based on the character of transitional chute and under the premise of no more difficulty on manufacture and installation，the paper analysis the force on turning point and make the conclusion as following:1）Magnitude of force on turning point is the main factor to effect the wear of transitional chute 2）The main effect to magnitude of force is not transitional angle but the angle between two level ring contacted with the same vertical ring.3）Bigger curvature radius of transitional arc is useful to lower the normal force on turning point.4）Higher chain speed is benefit to lower normal force on turning point.
Acknowledgements
This study was funded by Key Projects in the National and Technology Pillar Program during the Elev
enth Five-Year Plan Period. And the project number is 2007BAB13B01-02
Reference
[1] H.W. Wang, Q.Yao and X.G. Shi: Mining & Processing Equipment, V ol.·37(2009)No·14, p.96
(in –Chinese )
[2] Y.C. Zhao, W. Li and Z.W. Zhang: Coal Mine Machinery, V ol.·28(2007)No·8, p.58 (in
Chinese )
[3] L.P. Chen, Y.Q. Zhang, W.Q. Ren and G. Tan: dynamical analysis on mechanical system and
ADAMS (TsingHua University Press , China, 2005)

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