Study On Transmission Performances Of A Chain Conveyor With Path Constraint

Chain drive is an important driving mode in mechanical drive,which is widely used in agriculture,military industry and other fields.In some occasion where long pitch chains are used,chains are often bound in an orbit to reduce the chain vibration and improve the performance and life of the chain.The chain is analyzed from the design of constrained orbit,the impact load and vibrationBecause of the polygon effect of chains,the constraint trajectory must be an irregular curve.Based on the kinematic characteristics of constrained transmission chain with long pitch,the trajectory compensation of the chain is study in detail,and a series of calculation methods are obtained.Then the kinetic characteristics of the kinematics are studied.Finally,the calculation method of the constraint trajectory is applied to the design of the compensation trajectory of the U-type transmission chains,and the constraint trajectory of the chain is obtained under this special working conditions.Kinematics characteristics of the analysis is divided into two parts.The first part is the static analysis.Building the chain model witch include constrained pins and free pins.Firstly,analyzing each pin of the conveyor chain under static position.The second part is dynamic analysis.Speed and displacement of pins are calculated in one period,and the mathematical model of each pin in motion state is established.Free pins’ trajectory should include two parts is put forward due to the chain polygon effect.In static analysis,an approximate solution is proposed to solve the problem of nonlinear equations in chain drive mathematical model.In dynamic analysis,the key to the dynamic analysis of trajectory constraint transport chain is to solve the velocity of pins in transition.A solution is analyzed from two aspects toward the serious polygon effect of the conveyor chains with long pitch.For one thing,three types of models are established with different way of assembly.For another thing,the timing of getting on or getting off the wheels of chains is changed.The mathematical model of this conveyor chains is setup to calculate the velocity of pins in transition areas.The difference of the displacement of two pins in the right and left transition regions is used to reflect the strength of the polygon effect.The ways have no effect is excluded and finally a way to reduce the polygon effect is obtained.The conveyor chains bear a periodically shock loading due to the polygonal effect.The model of constrained path of conveyor chains with long pitch is built toward this issue.The model is divided into two parts: chain wheel and top edge.The kinetic model of the two parts are established based on the lagrange equation to calculate the generalized moment.In order to calculate the contact stress between the pins and other parts more precise,the models of chain wheel-pitch and pitch-pins are built by Abaqus.The generalized moment is used to calculate the maximum contact stress and its position on pins.The consequence may provide some reference for the selection of material and the method of heat treatment.Vibration is a main factor to influence the performance of chain drive.The difference between normal roller chains and constrained conveyor chains is that the main vibration mode of constrained conveyor chains is axial.The model and its equivalent model are established to solve this problem.The kinetic model is built to resolve the natural frequency and principal mode based on the vibration theory of multiple-degree-of-freedom system.The dynamic response in one period is obtained based on the forced vibration theory of multiple-degree-of-freedom system.The analysis shows that the value of natural frequency of constrained conveyor chains with long pitch is large and the vibration response in no-load operating condition is weak.In another word,the vibration is improved greatly with the constrained trajectory.