an implement frame indicated generally at 10 is shown only schematically in the present drawings , because it can be any desired type of frame such as those discussed in connection with the prior art identified above , or tool bar frames used for field cultivators and chisel plows and air seeders made by wil - rich , inc ., of wahpeton , n . dak ., the assignee of the present application . the frame 10 includes fore and aft extending frame members 12 , 12 which are spaced transversely apart and fixed in place with transverse frame members 13 . suitable cross braces 14 can be used on the frame 10 , if desired . cross members 15 are used adjacent the wheel mounting regions for additional strength . the lateral or transverse frame members 13 are used for mounting suitable earth working tools or other devices ( not shown ) such as field cultivator shank assemblies or chisel plow shank assemblies . the height of the frame 10 relative to the ground level is controllable with the device of the present invention by controlling the relative positions of a plurality of walking beam assemblies 20 , one of which is shown in the drawings . the walking beam assembly 20 carries spindles 22 , 22 on which the wheels 21 , 21 are mounted . the walking beam assembly 20 in turn is pivotally mounted on a support shaft 23 that is mounted at the end of an axle leg 24 . the upper end of the axle leg 24 is welded to an axle tube 25 . the axle tube 25 in turn is rotatably mounted in a pair of bearing supports 26 , 26 which in turn are supported on axle tube supports 27 , 27 . each of the axle tubes supports 27 is supported from a separate one of the force and aft frame members 12 , and the axle tube 25 is prevented from sliding axially relative to the bearing supports 26 by suitable stop members 28 which are welded to the tube but yet will permit the tube to rotate during adjustment of the axle leg . the vertical position of the wheels 21 , 21 relative to the frame is adjusted by controlling the pivoting of the axle tube . in many previous devices , the adjustment of height of the frame relative to the wheels has been accomplished by having the axle tube 25 act as a torsion shaft which is operated by a cylinder that is offset from the center line of the axle leg 24 . in previous lift arrangements substantial torsion loads were introduced into the axle tube , requiring heavier tubes with greater wall thicknesses and larger diameters than needed with the present lift . the device of the present invention eliminates torsion loads in the axle tube by providing a three bar linkage illustrated generally at 30 to support the loads on the axle leg from the wheels 21 and react the loads back to the frame . the three bar linkage includes a mast assembly 31 that comprises a pair of spaced members 32 which are rotatably mounted on the axle tube 25 through the use of a pair of mast bearing caps 33 , one of which is suitably attached to each of the members 32 . mast assembly 31 further includes a cylinder support ear 34 that is mounted between the members 32 , 32 at the upper ends thereof . ear 34 is provided with an aperture that receives a mounting pin 35 for pivotally mounting the base end of a double acting hydraulic cylinder assembly 37 to support ear 34 . the cylinder assembly 37 is operated through a suitable valve 38 to extend and retract a cylinder rod 41 . rod 41 has a clevis or rod end 42 pivotally mounted by a pin 43 to an ear 44 that is fixed to the axle leg 24 . an adjustable mechanical stop member 45 is mounted on the cylinder rod 41 so that the retracted position of the rod can be mechanically determined . the stop 45 will engage the end of the cylinder to provide a precise mechanical location for the lowest position of the frame . the stop 45 is adjustable to permit a fixed position to be achieved when retracting the cylinder assembly 37 . the force or load from the weight supported by wheels 21 that is reacted by the lift cylinder assembly 37 to the mast assembly is transmitted back to the frame 10 through a force link 50 . the mast , as previously explained , is free to rotate on the tube 25 . the force link 50 comprises a tube that is pivotally mounted at one end as at 51 between the mast members 32 , 32 of the mast assembly . a threaded adjustment rod 52 is threaded through a nut 53 which is welded to the end of the tube . the rod 52 can be threaded to change the length of the force link as desired . the lower end of the force link , comprising the threaded rod 52 , is mounted through an anchor assembly indicated generally at 55 that includes a cross member 56 that has an opening through which the threaded rod 52 is passed . lock nuts 57 are used for clamping the lower end of the rod 52 and thus the lower end of the force link securely to the anchor assembly . in addition to the cross member 56 , the anchor assembly has fore and aft extending members 58 that are attached to lateral frame members 13 and 15 with u bolts , as shown in fig1 so that the force link is securely anchored back to the implement frame . as mentioned , the force exerted on the axle leg 24 by the lift cylinder 37 is carried back to the mast assembly 31 which is free to rotate on the axle tube 25 , and the load is reacted through the force link 50 back to the frame . this puts the cylinder assembly 37 in compression and the force link 50 in compression while the mast assembly carries some tension . the axle tube 25 is not subjected to torsion loads during the raising and lowering operations . additionally , the length of force link 50 can be adjusted to compensate for wear and the stop 45 can be utilized for letting the lift cylinder return to a set position when it is retracted to lower the frame relative to the ground . thus , a simple framework is utilized by having a mast that pivots relative to the movable or pivoting axle support , which is directly centered on the axle leg . the linkage mechanism carrying the implement load forces are subjected to tension and compression load rather than torsion loads .
a lift mechanism for implements such as tool bar frames used with field cultivators and chisel plows includes means for eliminating torsional loading on the axle support and react vehicle loads through a three bar mechanism back to the frame . all structural members carrying loads are therefore stressed in compression or tension .