31、ration screen with a variable elliptical trace that is based upon an ideal screen motion for use in raw coal classification. The size of the vibrating screen is 3.6 m7.5 m,the feed granularity is 0 to 50 mm and the classification granularity is 6mm.Elliptically vibrating screens combine the basic ad 。

32、vantages of both circular and linear vibrating screens 9?10.The long axis of the ellipse determines material delivery and the short axis influences material loosening, to be exact.3 Dynamics model analysis of vibrating screen with variable elliptical traceWe made the exciting force deviate from the。

33、center of gravity,to change the motion pattern of the new vibrating screen.The stiffness matrix of the vibration isolation spring was not zero under these circumstances and the vibrating system had multiple degrees of freedom.Minor transverse wagging was neglected to simplify the research.The motion 。

34、 was considered to be a linear vibration of a rigid beam in the longitudinally symmetrical plane.At each point the vibration is a combination of the translation of the center of gravity and the screen pitching about the center of gravity.Previous studies neglected the influence of elastic forces in。

35、the horizontal and vertical direction on the swing of the vibrating screen 3,11.An accurate dynamic model consisting of three differential equations that include coupling of degrees of freedom in the vertical,horizontal and swing directions is proposed.The mathematical model of the vibrating screen。

36、is shown in Fig.2.The center of gravity, is taken as the origin of a rectangular coordinate system at staticequilibrium, in accordance with rigid motion on the plane 12.Simultaneous differential equations in generalized coordinates using center of gravity coordinates,x,y,and the swing declination an 。

37、gle, ,may be written aswhere M is the mass of the vibrating screens the moment of inertia of M relative to the center of gravity,O;
x and y the displacements in the x and y0directionas;
x and y the velocities in the x and y directions and y the accelerations in the x and y directions;
is the swing ang 。

38、ular displacement;
the installation angle;
fx,f yond father damping coefficients in the x,y and directions;
x k and k the stiffness coefficients of the supporting spring along the x and y directions;
A0 the amplitude of the exciting force, given by2 0 A mr, where r is the radius of eccentricity the ma 。

39、ss of the eccentric block and the exciting angular frequency;
L1 and L2 the distances between each supporting spring and the center of gravitys the distance between the rotating center of the eccentric block and the center of gravity;
and,the included angle between the l and x directions. The dampin 。

40、g force is rather small and can be neglected. Then Eq. 1 can be simplified to Eq.2.4 Motion and screening effect analysis of a vibrating screen with variable elliptical trace4.1 Analysis of the motion parameters Multiple degree-of-freedom vibration theory was used to find a stable solution for the f 。

41、orced vibration 13,as follows:When E 2 S 2 +C 2 H 2 +2 ESCH0, the trace of point D is a line. When E Sand C H, the trace of point D is a circle. In general. 6 expresses the equation of an ellipse.The xoy coordinate was rotated degrees anticlockwise to give a new set of x oycoordinates. A standard el 。

42、liptical equation was then obtained after eliminating D D x y in Eq.7.From this we know that some points on the screen move in a line or a circle while others move in an ellipse .As long as the relative position of the rotating center of the eccentric block and the center of gravity are properly adj 。

43、usted, variable elliptical motion of the screen will be obtained .This provides a reasonable throwing index and material delivery velocity and improves screening efficiency.4.2 Analysis of motion trace and screening efficiency The stable solution of a vibrating system, in terms of the vibrating scre 。

44、en, can be given byThe equations of motion for any point on the vibrating screen areEq.8shows that the center of gravity traces an approximate circle and that the amplitude in the horizontal and vertical directions is between 3.5 mm and 5 mm.Fig.3 shows how the center of gravity moves in three degre 。

45、es of freedom.Fig.3 gives theangular phase difference between the horizontal and vertical directions as well as the amplitude of the swing angle.5 Conclusions1A new vibrating screen with variable elliptical motion trace was proposed according to the principle of screening process with constant bed t 。

46、hickness.Different points on the vibrating screen trace differentelliptical paths.The motion pattern agrees well with the ideal motion characteristic for a screening surface. Thus,screening capacity and process efficiency can be increased.2A theoretical kinematic analysis of the vibrating screen was 。

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标题：变椭圆轨迹振动筛的动力学和筛选特性外文翻译可编辑|变椭圆轨迹振动筛的动力学和筛选特性外文翻译（可编辑）( 四 )