Design of a spring-loaded downforce system for a no-till seed opener

摘要

Constant downforce on a seeder disk opener is essential for maintaining a constant depth when seeding in no-till conditions. This study focused on the development of a mathematical optimization approach for the design of a no-till opener downforce system where the downforce would not change for more than +-10 and +-25 percent when the opener encounters minor (+-50 mm) and major (+-100 mm) micro-relief changes in a field, respectively. Two design alternatives, a spring-loaded single linkage and spring-loaded parallel linkage, were considered for the replacement of a hydraulically loaded downforce system. The prototype spring-loaded parallel linkage was tested in laboratory and in field conditions. When the opener unit ran over constructed obstaclesrepresenting a micro-relief change of +-50 and +-100 mm, the downforce (target values of 1023, 1360, and 1780 N) was varied by approximately +-13 and +-21 percent, respectively. Compared to the hydraulically loaded parallel linkage, the spring system resulted in approximately 50 percent smaller changes in downforce under the microrelief changes studied. Field tests revealed a faster response of the spring-loaded system. The design approach of minimising the change in opener downforce is an effective method to ensure that the design criteria for downforce variation are met.