Crop Machine with an Electronically Controlled Hydraulic Cylinder Flotation System

Abstract

In a crop harvesting machine there is provided a pair of hydraulic float cylinders for a header relative to a vehicle, where a float pressure to the cylinders is directly controlled by an electronic control supplying a variable control signal to a PPRR valve arrangement to maintain the float pressure at a predetermined value. At the set pressure a predetermined lifting force is provided to the header. A position sensor is used to generate an indication of movement and/or acceleration. The electronic control is arranged, in response to changes in the sensor signal, to temporarily change the control signal to vary the lifting force and thus change the dynamic response of the hydraulic float cylinder. In order to reduce static friction so that the system can react quickly, an arrangement is provided for causing relative reciprocating movement in an alternating wave pattern between the piston and cylinder.

1 . A crop machine comprising:
 a support vehicle for running over ground;   a crop component including a crop engaging system and at least one ground engaging component for providing a supporting force from the ground;   a support apparatus for supporting the crop component from the vehicle for upward and downward floating movement of the crop component so that a proportion of a supporting force is supplied by a lifting force from the support apparatus and a remaining portion is supplied by the ground engaging component;   the support apparatus including at least one hydraulic float cylinder having a piston movable in the cylinder arranged such that movement of the piston relative to the cylinder causes said lifting force to be applied to the crop component;   a first hydraulic circuit containing a hydraulic fluid for applying a pressure to a first side of the piston in the cylinder in a direction to lift the crop component;   the first hydraulic circuit being providing a pressure greater than that necessary to lift the crop component from the ground;   a second hydraulic circuit containing a hydraulic fluid for applying a pressure to a second side of the piston in the cylinder in a direction to lower the crop component;   a valve component in the second circuit for controlling the pressure of said hydraulic fluid to said second side;   and an electronic control system for supplying a control signal to the valve component so as to vary the hydraulic pressure in said second circuit so as to vary the lifting force.   
     
     
         2 . The crop machine according to  claim 1  wherein there is provided a sensor arranged to provide a sensor signal to said electronic control system in response to movement of the crop engaging assembly in said upward and downward floating movement of the crop engaging assembly, said electronic control system being arranged in response to said sensor signal to temporarily change the control signal to temporarily change the lifting force. 
     
     
         3 . The crop machine according to  claim 2  wherein said electronic control system is arranged subsequently in response to said sensor signal to revert to a set value. 
     
     
         4 . The crop machine according to  claim 2  wherein said electronic control system is arranged in response to changes in said sensor signal to temporarily change the control signal to vary the lifting force and thus change the response of the hydraulic float cylinder in response to detected movement of the crop engaging assembly. 
     
     
         5 . The crop machine according to  claim 2  wherein said electronic control system and said sensor are arranged in response to said signal to generate a value indicative of acceleration of the crop engaging assembly in said upward and downward floating movement of the crop engaging assembly. 
     
     
         6 . The crop machine according to  claim 2  wherein said electronic control system and said sensor are arranged upon detection of acceleration or movement in said upward floating movement to change the control signal to increase the lifting force to assist the acceleration in said upward floating movement. 
     
     
         7 . The crop machine according to  claim 6  wherein said electronic control system and said sensor are arranged upon detection of an end of acceleration in said upward floating movement to change the control signal to decrease the lifting force to dampen said upward movement. 
     
     
         8 . The crop machine according to  claim 2  wherein said electronic control system and said sensor are arranged to change the control signal to decrease the lifting force to a value less than said set value. 
     
     
         9 . The crop machine according to  claim 2  wherein said electronic control system and said sensor are arranged upon detection of acceleration or movement in said downward floating movement to change the control signal to decrease the lifting force to assist the acceleration in said downward floating movement. 
     
     
         10 . The crop machine according to  claim 9  wherein said electronic control system and said sensor are arranged upon detection of an end of said acceleration in said downward floating movement to change the control signal to increase the lifting force to dampen said downward movement. 
     
     
         11 . The crop machine according to  claim 2  wherein said sensor comprises a position sensor for generating as said sensor signal a position signal indicative of a position of the cylinder in said movement and wherein the electronic control system is arranged to calculate from the position signal a velocity and acceleration of the crop engaging assembly. 
     
     
         12 . The crop machine according to  claim 1  wherein said electronic control system is arranged to operate the electronic control system in dependence on an operating state of the crop engaging assembly. 
     
     
         13 . The crop machine according to  claim 1  wherein said electronic control system is arranged to provide a plurality of preset flotation system dynamics. 
     
     
         14 . The crop machine according to  claim 1  wherein said electronic control system is responsive to a ground speed signal to modify the changes in the control signal. 
     
     
         15 . The crop machine according to  claim 1  wherein the electronic control system includes an arrangement for causing relative reciprocating movement in an alternating wave pattern between said one component of said at least one float cylinder and said another component of said at least one float cylinder. 
     
     
         16 . The crop machine according to  claim 15  wherein said relative reciprocating movement is provided by an alternating wave pattern signal applied by said electronic control system to said valve arrangement to change said predetermined pressure in dependence on a value of the signal. 
     
     
         17 . The crop machine according to  claim 15  wherein said alternating wave pattern has an amplitude sufficient to cause the seals to break free from static frictional engagement with the component so as to maintain movement between the components at said cylinder seals to reduce static friction. 
     
     
         18 . The crop machine according to  claim 15  wherein said alternating wave pattern has a frequency in the range 5 to 15 Hz. 
     
     
         19 . The crop machine according to  claim 15  wherein said cylinder seals comprise annular seals between a peripheral surface of a piston head and an inside cylindrical surface of a cylinder. 
     
     
         20 . The crop machine according to  claim 15  wherein the alternating wave pattern is halted when the cylinder is used in a lifting or lowering state.