Cylinder synchronization for an implement lift system

[0001] The present invention relates generally to a hydraulic lift system for an agricultural implement and, more specifically, to a cylinder synchronization system for a multi-sectioned implement.

[0002] Previously available foldable multi-sectioned agricultural implements include a main frame and two or more wing frames hinged to the ends of the main frame. A rockshaft with a pair of parallel connected lift cylinders constrained for operation in unison by the rockshaft raise and lower ground engaging wheels on the main frame. Each of the wing frames includes a lift cylinder connected in series with one of the parallel connected cylinders so that the implement raises and lowers in generally level fashion. Often, a single point depth control having a valve connected to the hydraulic circuit provides an adjustable depth stop function on lowering of the implement. Lift wheels on the wing frames have to be moved to specific locations for implement folding to avoid unwanted contact with tools or frame members.

[0003] Rockshafts are heavy, expensive and cumbersome, and rockshaft windup results in uneven depth control. Recent implements have featured individually controlled lift wheel arms on the main frame without a rockshaft connecting adjacent arms. However, without a rockshaft, synchronization of the cylinders on the main frame with those on the wing frames is difficult. Providing a hydraulic lift system wherein the lift cylinders operate in unison across the entire width of the machine as the implement raises and lowers level continues to be a problem. Uneven loading on the implement frame causes differential extension and retraction of parallel connected cylinders. Although sophisticated cylinder control systems such as shown in commonly assigned U.S. Pat. No. 5,957,218 are available and work well for lift systems without rockshafts, some operators still prefer simpler conventional and less expensive hydraulic systems. Further, providing desired wheel tuck features for folding of the machine for transport and unfolding of the machine for field operations without wheel interference often requires expensive and complicated hydraulic circuitry.

[0004] It is therefore an object of the present invention to provide an improved implement lift system for a multi-sectioned implement having a plurality of lift cylinders. It is a further object to provide such a system which overcomes most or all of the aforementioned problems.

[0005] It is another object of the present invention to provide an improved implement lift system having level lift and lower characteristics without use of rockshaft connected cylinders. It is yet another object to provide such a system which maintains cylinder synchronization without need for complicated and expensive control circuitry.

[0006] It is another object of the present invention to provide an improved implement lift system for a multi-sectioned implement providing level lift and a wheel tuck feature that eliminates wheel interference during folding and unfolding of the implement sections.

[0007] A lift system includes parallel connected cylinder circuits with the rod ends of a pair of the cylinders mechanically tied together on a first lift wheel arm on the main frame so the cylinders are constrained to move in unison. The base end of a third cylinder connected to a second lift wheel arm on the main frame is connected to the same source of hydraulic fluid under pressure as the base ends of the pair of cylinders. The rod end of the third cylinder is constrained for movement with the rod end of a fourth cylinder also connected to the second wheel arm. The rod end of one of the pair of cylinders is connected in series with the base end of the fourth cylinder to thereby constrain the third and fourth cylinders on the second lift wheel arm to move in unison with the pair of cylinders on the first lift wheel arm. Series circuits connect the rod end of one of the cylinders in each pair with a base end of a wing section lift arm cylinder so the wing cylinders move in unison with the main frame cylinders to keep the implement uniformly level across all main frame and wing frame sections.

[0008] The hydraulic circuit is also plumbed to retract outer wing wheels during wing fold operations to eliminate outer wing wheel interference. A switch responsive to wing fold cylinder retraction operates a pair of electrohydraulic valves to interconnect the implement lift circuit with the implement wing fold circuit. Upon activation of the switch, pressurized hydraulic fluid from the fold circuit is directed to the rod end of an outer wing cylinder causing the cylinder to retract. With the wing wheels retracted and the switch activated, the main frame cylinders can be extended and retracted without affecting the outer wing cylinders. This feature allows the machine to be lowered while in the folded transport position to lower the overall height of the machine without extending the outer wing wheels. When the machine is unfolded, the switch will be deactivated to allow the outer wing wheel to extend and to isolate the fold circuit from the lift circuit. Upon switch deactivation, all implement lift cylinders operate independently of the fold circuit.

[0009] These and other objects, features and advantages of the present invention will become apparent from the description which follows and from the drawings.

[0012] Referring now to FIG. 1, therein is shown a multi-section agricultural implement 10 having a main frame 12 and inner and outer wing frames 14,16 and 18, 20. The main frame 12 is supported in a conventional fashion by vertically movable lift wheel assemblies 22 and 24. The lift wheel assemblies include wheels 26 supported at the end of a lift arms or linkages 28 pivotally connected to the frame 12. The innermost wing frames 14 and 16 are supported by lift wheel assemblies 34 and 36 in the field-working position and include lift arms or linkages 37 and 38. The outermost wing frames 18 and 20 are hinged to the frames 14 and 16 which, in turn, are hinged to the outermost ends of the main frame 12. Lift wheel assemblies 42 and 44 including lift arms or linkages 46 and 48 support the outer wing frames 18 and 20 above the ground when the frame is in the field-working position as shown. Hitch structure 50 is connected to the forward portion of the main frame 12 for towing by a tractor or other vehicle 52 (FIG. 2).

[0013] The inner wing frames 14 and 16 are hinged to the main frame 12, and wing fold structure 54 and 56 pivot the frames relative to the main frame between field-working positions (FIG. 1) and a narrowed transport position. The outer wing frames 18 and 20 are moved relative to the inner frames 14 and 16 between the field-working and transport positions by wing fold structure 58 and 60.

[0014] Referring to FIG. 2, the hydraulic circuit for the lift wheel assemblies and the wing fold structures for a five section implement is shown in detail. Lift cylinders 61 and 62 are connected to the right-hand outer frame lift arms 46 and 37. Main frame cylinders pairs 63, 64 and 65, 66 are connected to the lift arms 28, and the cylinders of each pair are mechanically constrained for extension and retraction in unison. Lift cylinders 67 and 68 are connected to the left-hand outer frame lift arms 38 and 48. The cylinders are rephrasing cylinders and each includes by-pass structure 70 at the rod end of the cylinder to provide cylinder rephrasing at full extension of the cylinder rod.

[0015] The wing fold structures 54 and 56 include a right inner wing fold cylinder 74 and a left inner wing fold cylinder 76. The wing fold structures 58 and 60 include a right outer wing fold cylinder 78 and a left outer wing fold cylinder 80. The cylinders are connected to hydraulic actuation and control circuit indicated generally at 84 in FIG. 2. The actuation and control circuit 84 includes selective control valve (SCV) structure 90 operably connected to a source of hydraulic fluid under pressure 92 on the tractor 52. SCV switches 94 and 96 control SCV outputs 100, 101 and 102, 103 respectively, which are connected by hydraulic lines and by valves 110, 112, and 114 to the cylinders 61-68 and 74-80.

[0016] The hydraulic cylinders 63 and 64 have rod ends connected together mechanically for extension and retraction in unison. The base ends of the cylinders 63 and 64 are connected together hydraulically and are connected to the base end of the cylinder 66 so the three cylinders operate in parallel. To assure the cylinder pairs 65, 66 move in unison with the cylinder pairs 63, 64, the rod end of the cylinder 63 is connected to the base end of the cylinder 65. As the cylinder 63 extends and retracts, the cylinder 65 is constrained hydraulically to extend and retract in like manner. The rod ends of the remaining three main frame cylinders 64, 65 and 66 are each connected in series circuit configurations with the wing frame cylinders 61, 62, 67 and 68. The rod end of the main frame cylinder 65 is connected to the base end of the left inner wing cylinder 67 so the cylinder 67 extends and retracts in unison with the cylinder 65. The rod end of the main frame cylinder 66 is connected to the base end of the right inner wing cylinder 62 for movement in unison. The rod end of the main frame cylinder 64 is connected through the valve 112 to the base end of the left outer wing cylinder 68 so that when the valve 112 is in the normal operating position shown in FIG. 2, the cylinder 68 extends and retracts in unison with the cylinder 64. The base end of the right outer wing cylinder 61 is connected to the rod end of the cylinder 68 so that the outer wing cylinders 68 and 61 operate in series and are controlled by the cylinder 64. Therefore, the three inner wing cylinders 64, 65 and 66 act as the control cylinders for the three series hydraulic circuits that operate the wing lift cylinders, and the cylinder 63 acts as the control cylinder for synchronizing the operation of the main frame cylinder pairs 63, 64 and 65, 66.

[0017] The base ends of the cylinders 63, 64 and 66 are connected through the normally open depth stop valve 114 to the SCV 1 output 100, and the rod ends of the cylinders 61, 62 and 67 are connected to the SCV 1 output 101. Assuming the cylinders 61-68 are extended and the implement 10 is raised so the depth stop valve 114 is in the open position shown, the operator can push the SCV 1 switch 94 forward to pressurize the output 100 connected to the rod ends of the cylinders 61, 62, and 67. The SCV 1 output 101 is returned to sump so the main frame cylinders 63, 64 and 66 can retract in unison with the wing frame cylinders. As the main frame cylinder 65 retracts with the cylinder 66, hydraulic fluid from the base end of the cylinder 65 passes to the rod end of the retracting cylinder 64 to maintain synchronization between the cylinder pairs 63, 64 and 65, 66. The series connections of the outer frame cylinders helps maintain a uniform levelness across the implement 10. The implement will continue to lower until the operator releases the SCV 1 switch 94 or until the depth stop valve 114 is closed as the implement reaches a prescribed operating depth. Once the operating depth is reached and the valve 114 closes, flow from the base ends of the cylinders 63, 64 and 66 is stopped, preventing further lowering of the implement and maintaining the implement in the depth stop position.

[0018] To raise the implement 10, the operator pulls the switch 94 to pressurize the output 100 and return the output 101 to sump. The depth stop valve 114 is responsive to pressure at the output 100 to move to the open position and allow flow from the output 100 to the base ends of the cylinders 63, 64 and 66 to extend the cylinders 61-68 in unison and raise the implement 10 in a level condition.

[0019] The wing fold cylinders 74, 76, 78 and 80 are connected in parallel and have rod ends connected to the SCV 2 output 103. The base ends of the cylinders 74-80 are connected together and to the SCV 2 output 102. When the operator pulls the SCV 2 switch 96 back, the output 103 will be pressurized to retract the fold cylinders 74-80. The outer wing cylinders 78 and 80 will retract first since there is less force required for the outer wing fold operation. Thereafter, the inner wing fold cylinders 74 and 76 will retract to fold both sets of wing frames 14, 18 and 16, 20 over the main frame 12. To reverse the operation and unfold the implement for field-working, the operator pushes the switch 96 to pressurize the SCV 2 output 102.

[0020] To eliminate outer wing tire interference, the circuit 84 is also plumbed to retract the outer wing cylinders 61 and 68 to cause the outer wing wheels to tuck into the wing frames during the fold operation. With the lift cylinders 61-68 extended and the implement in the raised position, the valves 110 and 112 are automatically activated (moved downwardly as depicted in FIG. 2) during wing folding. The valves 110 and 112 are activated in a conventional manner, such as by position-responsive switch structure located on the implement frame. The activation of the valves 110 and 112 interconnects the fold hydraulic SCV 2 outputs 102, 103 with lines connected to the outer wing cylinders 61 and 68. The rod end of the right outer wing cylinder 61 is connected to the SCV 2 output 103 pressurizing rod end of the cylinder 61 which, in turn, causes the series connected cylinder to retract. Hydraulic fluid from the base end of the cylinder 68 is returned to the fold circuit via valve 112. With the outermost wing wheels 26 retracted and the valves 110 and 112 activated, the main frame cylinders 63-66 can be extended and retracted without any affect on the outer wing cylinders 61 and 68. This allows the implement 10 to be lowered, for example to get through a low opening, without having to extend the outer wing wheels. When the valves 110 and 112 are inactivated and in the position shown in FIG. 2, all of the lift cylinders 61-68 operate independently of the fold circuit.

[0021] Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.