Twine tensioning device for a baler
A tensioning device is described for mounting between a knotter and a twine supply roll in a baler. The device comprises a spring biased tensioning arm 210 for taking up slack in the twine 216 and a clamp 220 for gripping the twine 216 at a location between the tensioning arm 210 and the supply roll. In the invention, the clamp 220 is coupled to the tensioning arm 210 in such a manner that the force applied by the clamp 220 to grip the twine 216 varies with the position of the tensioning arm 210.
1. A tensioning device for mounting between a knotter and a twine supply roll in a baler comprising: a spring biased tensioning arm for taking up slack in the twine and a clamp for gripping the twine at a location between the tensioning arm and the supply roll, wherein the clamp is coupled to the tensioning arm in such a manner that the force applied by the clamp to grip the twine varies with the position of the tensioning arm;
the clamp comprises two cogs that are spring biased towards one another between which the twine is frictionally gripped;
the cogs of which one is mounted on a stationary bracket and the other on a brace that is pivotable relative to the bracket about a pivot lying on a first side of the cogs and is urged by the spring on the second side of the cogs in a direction to increase the grip of the cogs on the twine passing between them, a guide means for the twine is secured to the brace on the same side of the cogs as the spring, wherein a twine contacting portion of the tensioning arm is also on the second side of the cogs;
wherein the twine tension exerts a force on the guide means in a direction to oppose the spring bias and to increase the separation between the two cogs, the force applied by the twine tension varying in dependence upon the position of the tensioning arm and;
wherein a pin is mounted on the brace on the opposite side of the guide means from the springs, the pin interacting with the twine when the tensioning arm moves to a position to take up slack in the twine to increase the force urging the cogs towards one another.
2. A tensioning device as claimed in claim 1 , wherein said guide means comprises a guide ring.
3. A tensioning device as claimed in claim 1 , wherein said guide means comprises a guide wheel.
4. A tensioning device as claimed in claim 1 , wherein the resulting force on the engaged twine increases towards the position of maximum clamping force and decreases towards the position of minimum clamping force.
5. A tensioning device as claimed in claim 1 , wherein the spring acting on the tensioning arm is positioned in such a way that the resulting force of the arm on the engaged twine varies with the force applied by the clamp.