Linear electric motor for an electric pruner

Manual and electric pruners used for tree pruning in industrial horticulture are insufficiently effective. An electric pruner with an improved magnetic circuit (a stator and an armature of the electric motor) and optimal energy characteristics will contribute to the effective development of the industry. The research aimed to develop a linear electric motor (LEM) for driving a manual electric pruner and to adapt its technical characteristics (cutting force) to the conditions of industrial horticulture. In the proposed LEM design, the cutting force is generated by two magnetizing coils (working and starting). The first coil is mounted on a stationary magnetic circuit, while the second is located on a magnetic system featuring a non-magnetic insert. The linear dimension of the armature non-magnetic insert was varied to 5, 10, and 15 mm. Theoretical values of the armature traction force depending on the size of the non-magnetic insert, obtained through simulation in the ElCut software, were compared with experimental data. The research results showed that the longer the non-magnetic insert, the greater the effective stroke length of the second (starting) coil. For a non-magnetic insert size of 5 mm, the stroke length was 3 mm, while for a 15 mm insert, it was 9 mm, respectively. It was established that with an increase in the size of the non-magnetic insert, the starting force decreases from 27 to 17 N. The total force generated by the two magnetizing coils enables the system to move at idle at the initial moment. At the end of the working stroke, under the action of the first (working) coil, a 6 mm diameter branch is cut with a force increasing from 25 to 132 N. The theoretical values of the total traction force practically coincide with the experimental curve. The obtained characteristics of the branch cutting force and the operation of the linear electric motor can be used in the design of manual electrified puners.

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