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A management system is disclosed for controlling the tension of an endless track by regulating the hydraulic pressure in a hydraulic jack acting on a roller serving to tension the track. The tension management system comprises two accumulators of different capacity that are connected to the jack. Bo

A management system is disclosed for controlling the tension of an endless track by regulating the hydraulic pressure in a hydraulic jack acting on a roller serving to tension the track. The tension management system comprises two accumulators of different capacity that are connected to the jack. Both accumulators are in permanent direct communication with the jack and the larger accumulator is preloaded to a higher pressure than the smaller accumulator.

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1. A tension management system for controlling the tension of an endless track by regulating the hydraulic pressure in a hydraulic jack acting on a roller serving to tension the track, the tension management system comprising:a first and a second accumulator each of different capacity that are conne

1. A tension management system for controlling the tension of an endless track by regulating the hydraulic pressure in a hydraulic jack acting on a roller serving to tension the track, the tension management system comprising:a first and a second accumulator each of different capacity that are connected to the jack, the smaller first accumulator being in permanent direct communication with the jack and the larger second accumulator being connected to the jack through a parallel combination of a pressure relief valve and a non-return valve, the pressure relief valve permitting flow of hydraulic fluid to the second accumulator when a predetermined opening pressure is exceeded in the jack and the non-return valve permitting flow from the second accumulator to the jack; a third accumulator that is permanently connected to the jack, the third accumulator having a greater capacity than the first accumulator and being preloaded to a pressure greater than the pressure of the first accumulator but less than the opening pressure of the pressure relief valve; and a throttled passage connected in parallel with both the non-return valve and the pressure relief valve. 2. A tension management system as claimed in claim 1, wherein the first accumulator has a capacity of 0.3 litres and a preloading of 30 bar, the second accumulator has a capacity of 2 litres and a preloading of 30 bar, the third accumulator has a capacity of 1 litre and a preloading of 150 bar and the opening pressure of the pressure relief valve is 220 bar.3. A tension management system as claimed in claim 1, wherein the first accumulator has a capacity of 0.3 litres and a preloading off 30 bar, the second accumulator has a capacity of 2 litres and a preloading of 30 bar, the third accumulator has a capacity of 1 litre and a preloading of 150 bar and the opening pressure of the pressure relief valve is 220 bar.4. A tension management system as claimed in claim 1, wherein the throttled passage is dimensioned to permit a maximum flow rate of 0.16 litres per minute.5. A tension management system as claimed in claim 2, wherein the throttled passage is dimensioned to permit a maximum flow rate of 0.16 litres per minute.6. A tension management system as claimed in claim 3, wherein the throttled passage is dimensioned to permit a maximum flow rate of 0.16 litres per minute.7. A tension management system as claimed in any of claim 1, wherein a safety valve is provided to connect the jack to a reservoir under atmospheric pressure if a maximum safe pressure is exceeded.8. A tension management system as claimed in any of claim 2, wherein a safety valve is provided to connect the jack to a reservoir under atmospheric pressure if a maximum safe pressure is exceeded.9. A tension management system as claimed in any of claim 3, wherein a safety valve is provided to connect the jack to a reservoir under atmospheric pressure if a maximum safe pressure is exceeded.10. A tension management system as claimed in any of claim 4, wherein a safety valve is provided to connect the jack to a reservoir under atmospheric pressure if a maximum safe pressure is exceeded.11. A tension management system as claimed in any of claim 5, wherein a safety valve is provided to connect the jack to a reservoir under atmospheric pressure if a maximum safe pressure is exceeded.12. A tension management system as claimed in any of claim 6, wherein a safety valve is provided to connect the jack to a reservoir under atmospheric pressure if a maximum safe pressure is exceeded.13. A combine harvester, comprising:an endless track; a hydraulic track tension management system in operative connection to the endless track, the hydraulic track tension management system for controlling the tension of the endless track by regulating a hydraulic pressure in a hydraulic jack acting on a roller serving to tension the track, the hydraulic track tension management system comprising: a first and a second accumulator each of different capacity that are connected to the jack, the smaller first accumulator being in permanent direct communication with the jack and the larger second accumulator being connected to the jack through a parallel combination of a pressure relief valve and a non-return valve, the pressure relief valve permitting flow of hydraulic fluid to the second accumulator when a predetermined opening pressure is exceeded in the jack and the non-return valve permitting flow from the second accumulator to the jack, and a third accumulator that is permanently connected to the jack, the third accumulator having a greater capacity than the first accumulator and being preloaded to a pressure greater than the pressure of the first accumulator but less than the opening pressure of the pressure relief valve, wherein a throttled passage is provided in parallel with both the non-return valve and the pressure relief valve; and an unloading auger positioned by means of the jack connected to the hydraulic pump, wherein the hydraulic pump of the unloading auger is connected by means of a normally closed valve to the hydraulic track tension management system, the normally closed valve in an open position operable to permit the hydraulic pump of the unloading auger to charge the hydraulic track tension management system. 14. A combine harvester, comprising:an endless track; a hydraulic jack; a roller operatively connected to the hydraulic jack and the endless track; and a tension management system for controlling the tension of an endless track by regulating the hydraulic pressure in the hydraulic jack acting on the roller serving to tension the track, the tension management system comprising: a first and a second accumulator each of different capacity that are connected to the jack, the smaller first accumulator being in permanent direct communication with the jack, a parallel combination of a pressure relief valve and a non-return valve connecting the larger second accumulator to the jack, the pressure relief valve permitting flow of hydraulic fluid to the second accumulator when a predetermined opening pressure is exceeded in the jack and the non-return valve permitting flow from the second accumulator to the jack, a third accumulator permanently connected to the jack, the third accumulator having a greater capacity than the first accumulator and being preloaded to a pressure greater than the pressure of the first accumulator but less than the opening pressure of the pressure relief valve, and a throttled passage connected in parallel with both the non-return valve and the pressure relief valve. 15. A combine harvester as claimed in claim 14, further including an unloading auger positioned by means of the jack connected to the hydraulic pump.16. A combine harvester as recited in claim 15, wherein the hydraulic pump is connected by means of a normally closed valve to the hydraulic track tension management system, the normally closed valve in an open position operable to permit the hydraulic pump to charge the hydraulic track tension management system.17. A combine harvester as claimed in claim 14, wherein the first accumulator has a capacity of 0.3 litres and a preloading of 30 bar, the second accumulator has a capacity of 2 litres and a preloading of 30 bar, the third accumulator has a capacity of 1 litre and a preloading of 150 bar and the opening pressure of the pressure relief valve is 220 bar.18. A combine harvester as claimed in claim 14, wherein the first accumulator has a capacity of 0.3 litres and a preloading of 30 bar, the second accumulator has a capacity of 2 litres and a preloading of 30 bar, the third accumulator has a capacity of 1 litre and a preloading of 150 bar and the opening pressure of the pressure relief valve is 220 bar.19. A combine harvester as claimed in claim 14, wherein the throttled passage is dimensioned to permit a maximum flow rate of 0.16 litres per minute.20. A combine harvester as claimed in claim 14, further including a safety valve configured to connect the jack to a reservoir under atmospheric pressure if a maximum safe pressure is exceeded.