Design And Research On Key Structure Of Spherical Hedge Trimmer

For the maintenance of spherical hedges,most of the existing equipment is used to trim flat hedges.In order to trim the spherical hedge,it is necessary to customize the trimming cutter of the specified radius,which will increase the cost of the greening maintenance work.Therefore,it is of great significance to research and develop pruning equipment that can prune spherical hedgerows with different radii.The spherical hedge trimmer studied in this paper consists of three parts:lifter,telescopic mechanism and pruning mechanism.The telescopic mechanism uses a telescopic boom that electrically drives a rope pulley,which is lighter in weight than traditional hydraulic telescopic booms.One side of the tpruning mechanism is a diamond-shaped mechanism for adjusting the angle between the cutters,and the other side is a link transmission mechanism for the reciprocating movement of the cutter.The lifter and telescopic mechanism are used to adjust the position of the pruning mechanism.The motor at the end of the telescopic mechanism drives the pruning mechanism to rotate.The trimming mechanism can trim spherical hedges with different radii within a certain range,which has the characteristics of high efficiency and low cost.First,the main structure of the spherical hedge trimmer was determined by analyzing the working environment of the spherical hedge trimmer and compared with the existing spherical hedge trimmer.Two design schemes about the spherical hedge trimmer are innovatively proposed according to the design requirements.Through the comparative analysis,the design scheme of the electric drive rope pulley telescopic boom and the design scheme of the trimming tool based on the link transmission are determined,which solves the problem that the curvature radius of the spherical hedge cutter is not adjustable.Secondly,the performance parameters of the lifter,telescopic mechanism and trimming mechanism are determined through analysis and calculation.The three-dimensional model of the key mechanism is established through UG software,and the kinematics analysis is performed in the ADAMS software.The working time of each key organization is allocated according to the pruning process.In the kinematics simulation,the lifter is given four kinds of driving functions according to the working time.The analysis results show that the movement of the lifter is the most stable when the working time is 60 s.During the kinematics simulation of the telescopic mechanism,five kinds of driving ropes with different diameters are given.Through the stability analysis of the three-section boom and the rope tension,the rope diameter is determined to be 12.5 mm.The trimming mechanism is given 5 different crank-link ratios.By comparing the movement stability of the movable knife and the force of the connecting rod,the ratio of the crank and connecting rod of the trimming mechanism is determined to be 3:10.Then,the specific dimensions of the key mechanism are designed through static analysis and modal analysis.The trapezoidal reinforcement of the lifting platform is divided into 7 gradients and subjected to static analysis.The results of the comparison and analysis show that the lengths of the upper and lower bottoms of the trapezoid are 60 mm and 30 mm.The thickness of the shear fork arm was determined to be 30 mm through static analysis of the s shear fork arm lifter with different thicknesses.The thickness of the upper and lower plates of the telescopic mechanism is given.The thickness of the side plate was determined to be 5 mm,by changing the thickness of the side plate and performing finite element analysis.The driving links and L-shaped guide plates with different thicknesses in the trimming mechanism were analyzed.The comparative analysis results show that the thickness of the transmission link and the L-shaped guide plate are determined to be 3 mm and 5 mm.The natural frequency of each mechanism is much greater than the excitation frequency is verified through modal analysis.Finally,an accurate dynamic model of the telescopic mechanism is established,by simplifying the rope to a massless spring model and introducing friction term.The analysis results show that the system has resonance at the angular frequency ?0=324.The system transfer function is corrected by introducing double-T networks and proportional component.In this paper,the structural design,simulation analysis and parameter optimization of the key mechanism of the spherical hedge trimmer are studied.The structure meets the strength and stiffness conditions.The structure design of the spherical hedge trimmer meets the requirements of working conditions and overcomes the shortcomings of the common hedge trimmers on the market.