| Banknote is one of the important circulation mediums in national economic activity.Because banknote has the characteristics of light weight,thin material,easy deformation,and it is often in a folding state in the circulation process.At present,to deal with this kind of banknotes mainly depends on hand.Flattening of flexible banknotes is that the banknotes folded randomly are opened into flat state by mechanical means,so as to satisfy the receive requirements of automation financial equipment for banknotes.The technology research and equipment design theory for the flattening of flexible banknotes is very few at home and abroad,and has not yet formed a systematic theoretical system.In this paper,the technical principle and the structure design scheme of the flexible banknotes are presented,and the key technologies are analyzed,simulated and verified.Aiming at the characteristics of random banknote stacking,this paper proposes a method of adsorption with variable-aperture,which realizes the single picking and stable transportation of banknotes.In this paper,the pressure distribution of the negative pressure chamber is studied,combined with negative pressure and pressure,and the numerical simulation model is established by using the explicit dynamic method to take the tensile load under the negative pressure.Analyzed the mechanical properties of the banknotes during the loading process,and obtained the critical tensile force that the banknotes can bear under the suction of the negative pressure and the influence of the suction hole structure on the critical tension.The results show that the width of the side hole and the distance between the side hole and the center hole have a significant effect on the critical tension of the banknotes,and increasing the width of the side hole and the distance between the two holes can improve the adsorption performance.According to the technical principle of banknote flattening,the adsorption method of negative pressure roller with controllable adsorption zone is proposed.The pressure distribution of the drum cavity is studied,and the numerical simulation model of the load of the banknotes under the roller adsorption is established.The influence of suction cup on the critical tension is studied.The influence of the suction force of the drum on the critical tension was studied.The results show that the distance between the suction holes in the circumferential direction of the roller has a significant effect on the critical tension of the banknotes.Increasing the aperture and the circumferential spacing can improve the adsorption performance of the banknotes.A method of banknotes unfolding based on differential friction principle under the negative pressure zone is presented.The governing equations of the morphological evolution in the unfolding process of the folded banknotes are derived.Using the modified Coulomb friction model and the banknotes torsion spring model,the dynamic equation of the banknotes unfolding is established.And the dynamic equations are solved numerically by using the four order Runge-Kutta method.A finite element model is established for the process of the banknotes unfolding when the system is under negative pressure situation.Meanwhile,this paper analyzes the mechanical characteristics and defines evaluation standard for the process of the banknotes unfolding,and studies the influence of roller parameters on the quality of banknotes under negative pressure situation.The results show that the influence of the contact distance between the roller and the negative pressure zone on the quality of banknotes is the most significant.When the contact distance is in the range of 0.1mm~0.18 mm,with the increase of the contact distance,the quality of banknotes is obviously reduced.When the design speed of negative pressure zone is 0.5m/s,and the roller diameter is 15 mm,in the range of 21r/s~63r/s speed,the change of the roller speed has little effect on the quality of the banknotes.The diameter of roller wheel also has a significant impact on the unfolding form of banknotes.When the diameter is larger than 30 mm,the banknotes appears to be folded and broken,and the degree of fold increases with the increase of the diameter of the roller.A statistical analysis of the folding form of banknotes is made,and these folded banknotes are divided into four types.According to the folding categories,the paper puts forward a banknotes unfolding method of double drum exchange adsorption.The governing equations of the shape evolution for the process of the banknotes unfolding are derived,and the dynamic equation of the banknotes unfolding process under drum adsorption is set up and solved by numerical method.A finite element model is established for the process of the banknotes unfolding when the system is under drum adsorption.Meanwhile,this paper analyzes the mechanical characteristics for the banknotes unfolding process,and studies the influence of roller parameters on the quality of banknotes.The results show that the contact distance between the roller and the cylinder is in the range of 0.07mm~0.19 mm,with the increase of the contact distance,the quality of banknotes is increased firstly and then decreased.When the contact distance is 0.1mm,the quality of the paper currency is the best.When the roller design diameter is 400 mm,the rotational speed is 1r/s,when the roller diameter is 15 mm,in the 54r/s~158r/s rotational speed range,the quality of banknotes is improved with the increase of the wheel speed.When the roller diameter is in the range of 15mm~45mm,with the increase of the diameter of the roller,the quality of banknotes is increased firstly and then decreased.When the roller diameter is 25 mm,the quality of the banknotes is the best,and the quality of banknotes is reduced sharply after the roller diameter more than 25 mm.An experimental platform for the adsorption of banknotes was set up,The critical tensile forces for banknotes under the negative pressure zone and the drum are tested,and compared with the numerical simulation results.The results show that the difference between the critical tension and the simulation results is within the reasonable range.The critical tensile forces of two kinds of methods are basically consistent with the change of suction hole structure.The numerical analysis method can be used to guide the design for the structure of the banknotes adsorption devices. |
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