A baler comprising: a bale chamber ; a plunger configured to compress crop material in said bale chamber in order to form a bale; a needle yoke with a plurality of needles configured to deliver twine through said bale chamber ; a plurality of knotters configured to receive the twine from said plurality of needles; a bale length measurement and trigger device configured to measure the length of the bale in the bale chamber and to generate a trigger when a predetermined length is reached; a driving shaft located above the bale chamber and extending in a traverse direction of the baler; wherein the driving shaft is coupled with a gear box configured to continuously rotate said driving shaft when the baler is in operation; a needle coupling device between the driving shaft and the needle yoke , said needle coupling device being configured for moving said needle yoke from a rest position to a twine delivery position and back, when said bale length measurement and trigger device generates a trigger; characterised in that the needle coupling device comprises: a crank arm attached to the driving shaft and co-rotating with the driving shaft ; and a plurality of coupling members between said crank arm and said needle yoke , wherein said plurality of coupling members is configured for establishing a coupling between the crank arm and the needle yoke when said bale length measurement and trigger device generates a trigger. a bale chamber ; a plunger configured to compress crop material in said bale chamber in order to form a bale; a needle yoke with a plurality of needles configured to deliver twine through said bale chamber ; a plurality of knotters configured to receive the twine from said plurality of needles; a bale length measurement and trigger device configured to measure the length of the bale in the bale chamber and to generate a trigger when a predetermined length is reached; a driving shaft located above the bale chamber and extending in a traverse direction of the baler; wherein the driving shaft is coupled with a gear box configured to continuously rotate said driving shaft when the baler is in operation; a needle coupling device between the driving shaft and the needle yoke , said needle coupling device being configured for moving said needle yoke from a rest position to a twine delivery position and back, when said bale length measurement and trigger device generates a trigger; characterised in that the needle coupling device comprises: a crank arm attached to the driving shaft and co-rotating with the driving shaft ; and a plurality of coupling members between said crank arm and said needle yoke , wherein said plurality of coupling members is configured for establishing a coupling between the crank arm and the needle yoke when said bale length measurement and trigger device generates a trigger. a crank arm attached to the driving shaft and co-rotating with the driving shaft ; and a plurality of coupling members between said crank arm and said needle yoke , wherein said plurality of coupling members is configured for establishing a coupling between the crank arm and the needle yoke when said bale length measurement and trigger device generates a trigger. <EOS>