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DC motors reduce the weight of electric pruning shears

DC motors reduce the weight of electric pruning shears

Anyone who has already suffered from mouse arm or tennis elbow knows exactly about painful and persistent RSI. Even the smallest movement can cause extreme and long-lasting damage to muscles, tendons and nerves, if it is repeated thousands of times. If mouse arm results from operating computers, the equivalent for wine and fruit growers, who must trim countless branches and shoots, is ‘shearing arm’. 

In order to counter the risk of injuries due to repeated movement patterns and support the muscles, many people now use motorised shears. The Pony model from Italian manufacturer Campagnola is a particularly lightweight, low-power device that works with a Faulhaber DC micromotor (available in the UK from EMS) in order to offer the highest efficiency at the lowest weight. Each vine can make dozen of shoots each year but only one or two are necessary for the production of wine. All redundant shoots are cut off directly at the roots and the remaining shoots are pruned which means at least one cut per shoot. Each hectare contains between 5,000 and 10,000 vines, which means that approximately 100,000 cuts per hectare must be done alone in wine growing. 

Every cut, which is placed with simple pruning shears, requires considerable effort from the arms and hands and leads to symptoms of fatigue after a certain amount of time. The risk of contracting RSI is extremely high, particularly during the cutting phase. In order to prevent this, device manufacturers developed mechanical pruning shears as soon as the technical requirements were available. At the beginning, pneumatic systems were the only mechanical solution, but today batteries are replacing compressors.

Electric shears are connected to a lithium-ion battery which is normally fastened onto the wine grower’s belt with a short cable while the electrical motors are integrated into the shear’s handles and apply the necessary force. Campagnola technical director Patrizio Pellicanò explains: “During the cutting season, the operator must often use the shears relentlessly for weeks. This means that the operator must hold the device for the entire day and every gram of weight counts.”

The motor is the crucial component but not only in regards to its weight. “The drive must have high torque while the weight is reduced to a minimum,” explains Christian Lucini of Faulhaber. “It must also work at high speeds in order to make the cuts as quickly as possible. Due to the start-stop nature of this work with constant load changes, the shears must also provide force without warming-up while the energy consumption is minimised and the operating time maximised.”

Campagnola carried out a series of tests comparing the drives of different manufacturers based on these criteria. “The 2657 CR DC micromotor from Faulhaber clearly won the comparisons,” recollects Pellicanò. “With just 156 grams for the motor, the entire drive system weights 80 grams less than other motor-gearhead combinations. In addition to this, high efficiency in combination with low energy consumption provide a usage duration of ten hours per charge, which corresponds to 20% more battery life in comparison to rival products.”

The Pony model is the lightest pair of shears that Campagnola offers and one of the lightest models on the market. It can perform up to 70 cuts per minute and can be operated both automatically and manually. In automatic mode, the cutting blades fully close as soon as the finger presses the trigger. In manual mode, the cutting blades conform to finger movements, which means that the motor reacts very precisely and the output power must be adjusted exactly to the movement. The DC-motor manages this fine coordination with flying colours. 

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