The Study On The Structure Of Large-scale Plunger Cylinder With Double Spherical Joint

As an actuator, the plunger type cylinder has been widespread used on the structureof large-scale hydraulic press. The double spherical structure is the major joint formbetween the plunger and the moving beam. When the hydraulic press received theoff-center load, the plunger deflected, contacted with the guide and seals, then producedthe side thrust which may speed up the wear and tear. So that, the effect of side thrustbecame a core evaluation criteria when the double spherical structure was discussed.Including the two spherical hinges and a connecting rod between them, there are threemain parts in the double spherical structure. In the traditional hydraulic design theory, it isthe most important ways to reduce the side thrust by increasing the length of connectingrod and decreasing the radius of spherical hinges. However, the reality is not that.Contrasted with the previous theory, there are some differences in the designs hydraulicpress nowadays, especially on the large-scale plunger cylinder, even have not a clearevaluation for the major sizes on the structure of double spherical joint .First, the research on the mechanism of side thrust as a beginning, on the off-centerload condition, do the force analysis about the structure above, then discussed the differenteffects on the side thrust of plunger when changing the contact conditions. Based on largenon-linear finite element software MSC.Marc as the platform, the three-dimensional finiteelement simulation model was established. Through a lot of numerical simulations, theinfluencing rule of spherical hinge radius, the rod length and guide clearance on the sidethrust were summarized systematically. The research shows that: With the same sphericalstructure, the different contact positions may lead the different ways and effects on theside thrust. Under the same contact condition, the thrust decreases with the increase of therod length and the rod diameter. The thrust increases with the increase of the sphericalhinge radius. The thrust decreases with the increase of the guide clearance.In this paper, a experimental plunger cylinder and a test device was produced as theprototype of 125 MN forging hydraulic press according to the proportion of 1:10, whichequipped with five groups of different sizes of rods and hinges. Experiments on the test ofthe side thrust were done in the work conditions of off -center loads. Through the data getting from transducers, The comparison between the result of experiments and thetheoretical analysis can be done as a proving. The experimental result shows that the rulesgot by theoretical analysis are basically true.Through the whole research on the double spherical structure: In the engineeringdesign, the rod length factor: 0.64~0.83. the rod diameter factor: 0.59~0.63. the sphericalhinge radius factor: 1~1.15.