Agricultural implement and method of controlling an agricultural implement

1. An agricultural implement for working soil across which the agricultural implement travels or is towed, comprising:

a frame;

a first depth maintaining unit, comprising a pair of first hydraulic actuators to adjust a height of the first depth maintaining unit relative to the frame;

a second depth maintaining unit, comprising a pair of second hydraulic actuators to adjust the height of the second depth maintaining unit relative to the frame;

at least one soil-working tool; and

a hydraulic system comprising the first and second hydraulic actuators, which is connectable to valves configured to supply hydraulic fluid to the hydraulic system;

wherein

first sides of the first hydraulic actuators communicates with first sides of the second hydraulic actuators;

second sides of the first hydraulic actuators communicates with second sides of the second hydraulic actuators; and

wherein at least one sensor is configured to provide a measured value corresponding to a first amount of hydraulic fluid occurring on said first sides or on said second sides.

2. An agricultural implement according to claim 1 , wherein said first sides of said first and second hydraulic actuators have a common supply line.

3. An agricultural implement according to claim 1 , further comprising a control unit configured to control said hydraulic system, the control unit configured to communicate with said at least one sensor.

4. An agricultural implement according to claim 1 , wherein said at least one sensor is configured to measure a position of one of the hydraulic actuators.

5. An agricultural implement according to claim 1 , wherein said at least one sensor is configured to measure an angle position of an arm associated with one of said depth maintaining units.

6. An agricultural implement according to claim 1 , wherein at least one of said first and second hydraulic actuators comprises at least two hydraulic cylinders.

7. An agricultural implement according to claim 6 , wherein said at least two hydraulic cylinders are connected in series.

8. An agricultural implement according to claim 6 , wherein said at least two hydraulic cylinders are connected in parallel.

9. An agricultural implement according to claim 1 , wherein said first and second hydraulic actuators have different length of stroke and/or piston area.

10. An agricultural implement according to claim 1 , wherein said first and second depth maintaining units are located at a distance from each other as seen in a direction of travel of the agricultural implement.

11. An agricultural implement according to claim 1 , wherein said first and second depth maintaining units are located at a distance from each other as seen in a transverse direction of the agricultural implement.

12. An agricultural implement according to claim 1 , wherein said first and second depth maintaining units comprise a first and a second supporting part, respectively, for engagement with the soil, which supporting parts are selected from a group consisting of a wheel, a packer wheel, a rubber roller, a steel roller, and a ribbed packer roller.

13. An agricultural implement according to claim 1 , wherein said soil-working tool is selected from a group consisting of a cultivating tine, a harrow tine, a levelling implement, a harrow disc, a plough bill, a seed furrow opener, a seed knife, a seed furrow closer, and a sowing disc.

14. A method of controlling the depth level in conjunction with an agricultural implement according to claim 1 , comprising:

receiving, during use of the soil-working tool of the agricultural implement in a working position, a measured value corresponding to a first amount of hydraulic fluid on a first side of the hydraulic system;

operating the hydraulic system for lifting of the tool to a turning position or a transport position, a second amount of hydraulic fluid occurring on said first side of the hydraulic system; and

based on the received measured value, restoring the first amount of hydraulic fluid on said first side of the hydraulic system.