IMPROVED DRAUGHT FRAME

Abstract: A draught frame for a towed vehicle, such as a cultivator (12), has a draw bar (16) with a rearwardly extending section (34) overlying the front part of the cultivator main frame (14). Draught loads are transferred between the main frame (14) and the depending section (34) by a pair of arms (38, 39) pivoted on transverse pivot axes (41, 42, 43). The relative angle between the arms (38, 39) and the spacing thereof result in the arms defining an instantaneous centre (47) through which the resultant of the draught forces act.

Description: IMPROVED DRAUGHT FRΛME Background of the Invention This invention relates to an improved draught frame and relates particularly to an improved draught frame for tillage equipment, earth working equipment and the like adapted to be towed by a prime mover such as a tractor. Tillage implements such as .cultivators and ploughs are generally constructed for towing by a prime mover and are connected to the prime mover by means of a draught frame which is integral with or rigidly connected to the working frame of the implement. The draught forces comprise the towing force applied through the connection of the implement with the prime mover and acts along a line substantially parallel with the ground and spaced above the ground by a distance corresponding to the hitching height. This force is counteracted by the substantially horizontal forces acting on the ground working tools. The ground working tools may be tines, plough shares, scraper blades, rippers or the like, and the forces acting on those tools acts in a direction opposite to the draught force at some point on or below the surface of the ground. The vertical displacement of these forces i.e. the draught force and the resistant force, constitutes an unbalancing couple, the resulting moment of which tends to rotate the implement about a transverse line causing variations in tool penetration depth and control. With agricultural tillage implements such as cultivators, the resultant moment is counteracted to some degree by the weight of the implement as well as, in some cases, by the shape of the implement tools engaged in the ground. However, as the resistant force varies in accordance with soil consistency, depth of penetration, tool condition, nature of terrain and numerous other factors, it is virtually impossible to maintain a constant depth of penetration of the working tools. Further, constant depth control of both the forward and rear portions of the implement is extremely difficult due to instantaneous variations in the unbalancing couple. These difficulties are particularly noticeable in seed bed preparation and seeding operations when the depth of seeding must be critically controlled. Background Art Various forms of draught frame and draw bar constructions have been proposed in an endeavour to reduce the aforesaid problems. However, while some constructions utilizing a pivoted draw bar with front and rear wheels to follow contours do result in an improved control of tool penetration, the unbalancing couple remains to cause errors in operating control. European Patent Application 84302810.1 (Publication No. 0 123 561) discloses a flexible tine harrow for seed bed preparation, the harrow comprising a number of separate harrow sections each having an intermediate frame supported by front and rear drums. The intermediate frames are connected to a main frame through a front, fixed length link at the front of the intermediate frame and by a tele¬ scopic stay biased to extension and arranged above the harrow sections. The direction of push and pull forces exerted through the link connection and the stay result in a horizontal resultant force at the point of intersection on a level with the harrow tines which reduces or balances the unbalancing couple. However, the flexible tine harrow construction disclos'ed requires three separate frame structures inter- connected to permit relative angular adjustment, the frame sections being individually supported on drums and rear- wardly disposed wheels. The structure "does not readily lend itself to relatively heavy ploughs and cultivator equipment. It is therefore an object of. the present invention to provide an improved draught frame structure which goes someway towards overcoming problems of the known draught frames . It is also an object of the invention to provide draw bar and draught frame structures which enable increased control of working tool ground penetration. It is also desirable to provide agricultural implements having means to avoid at least some of the difficulties noted above. It is also desirable to provide agricultural or other equipment with an improved draught frame arrangement to minimize variations in soil penetration of the working tools. It is further desirable to provide draw bar and draught frame structures havirig an interconnecting arrange¬ ment to effectively move the plane of interconnection away from the plane of actual connection. It is further desirable to provide an improved draught frame whereby the resistance forces on the implement being moved are effectively transferred to vertical forces on the prime mover tow bar. * Summary of the Invention According to one aspect of the invention there is provided a connection between the working frame means. of an agricultural implement and a draught frame means, said connection comprising a pair of longitudinally spaced links pivotally interconnected to each of the working frame means and draught frame means, the pivotal interconnection being -arranged such that a line containing the axes of the pivotal connection of one link .intersects a line containing the axes of the pivotal connection of the other link at a desired point spaced below the working frame means. Preferably, the desired point is at or below the surface of the ground near the level at which soil resistance is applied to working tools on the working frame means. The linkage creates a virtual hinge point at the point of intersection of the lines connecting the axes of the pivotal connections which causes the working frame to act as if it were flexibly connected to the draught frame means by a hinge located at the instantaneous inter¬ section of the intersecting lines. Thus, the force couple normally produced by the draught and soil resistance is removed from the working part of the implement and trans¬ ferred to another part where its effect does not adversely affect the operation of the implement. By suitable proportion, the desired point of intersection can be caused to lie in the plane of the soil resistance forces thereby eliminating any rotative moment from the working frame means. It will be understood that, with this arrangement, by placing support wheels at the front and rear of the working frame means, the working frame is able to follow soil undulations without significant changes in depth of penetration between the front and rear of the working frame means. This is of vital importance in tillage and sowing operations. According to another aspect of the invention there is provided a draught frame structure comprising a draw bar means having a front end to be connected to a prime mover, equipment frame means supported on wheels, and first and second load transfer parts to transfer draught and resistance forces between the draw bar means and the equipment frame means, said first and second load transfer parts-interacting to define an instantaneous centre through which the resultant of the draught and resistance forces act. In a preferred form of structure, such as an agricultural implement, the first and second load transfer parts comprise a pair of longitudinally spaced arms one end of each of which is pivotally connected to the draw bar means and the other end of each of which is pivotally connected to the frame means, the pivotal connection axis extending transversely and being so located that lines passing through the respective connections for each arm intersect at or adjacent the horizontal plane along which the resistance forces act. In another form, the first and second load transfer parts comprise a curved track member mounted on either the draw bar "or frame means and interacting roller means mounted on the other, the curved track means having an instantaneous centre at or adjacent the plane along which the resistance forces act and the roller means transmitting draught forces in the direction of the instantaneous radius of said curved track corresponding to the roller means position. The invention more particularly comprises an agricultural implement comprising a main frame carrying ground working tools, wheels supporting the main frame above the ground, a draw bar to connect the main frame to a prime mover, the draw bar having two legs diverging rearwardly from the front thereof and terminating in spaced, substantially parallel rear end portions overlying a front part of the main frame, a pair of front links connected by transverse pivots to the respective rear end portions and the main frame, the front links extending downwardly and rearwardly from the rear end portions of the draw bar legs, a rear link longitudinally spaced from each respective front link and connected by transverse pivots to the respective rear end portions and the main frame, the rear links extending downwardly and forwardly from the rear end portions. In one embodiment, the front and rear links of each pair define lines which intersect at or near ground level at any instance during use. Thus, the effective draught force on the main frame acts at about the same level as the resistance forces thereby reducing or removing the couple tending to unbalance the implement. By effectively lowering the line of action of the draught forces, the power required to move the implement is substantially reduced, the control of tool penetration is substantially increased and the accuracy of penetration control is greatly enhanced. The invention is therefore of particular advantage for cultivators and seeders. In order that the invention is more readily understood and able to be put into practical effect, embodiments thereof will now be described with reference to the accompanying drawings. Description of the Drawings Figure 1 is a part top plan view of a cultivator incorporating the structure of the invention, Figure 2 is an enlarged part plan view illustrating features of the invention shown in Figure .1, Figure 3 is a part sectional side elevational view of the cultivator of Figure 1, Figures 4 to 6 are further side elevational views showing operational features of the invention, and Figure 7 is a side elevational view of another embodiment of the invention. Description of the Preferred Embodiments Referring to Figures 1 to 3 of the drawings there is illustrated a cultivator.12 which is adapted to be towed by a prime mover (not shown) . The cultivator 12 comprises a main working frame 14 carrying cultivator tines 22. A side frame 15, also carrying cultivator tines 22, is pivotally mounted on each side of the main frame 14 by pivot mounts 20. Only a portion of the side frames 15 is illustrated in the drawings. Wheels are provided on the outer ends of the side frames 15 for support thereof. The main frame 14 is supported above the ground by a pair of rear wheels 21 and two pairs of front wheels 23. The wheels of each front pair 23 are carried by a longitudinally extending beam 24 pivotally connected at approximately its midpoint to a transversely extending torque box 26. The torque box 26, in turn, is carried by a pair of bell crank levers 27 which is pivoted to the main frame 14. The rear wheels 21 are each carried by an arm 28 pivoted to the main frame 14 and connected, at one end, to the respective bell crank lever 27 by a tension rod 29. A hydraulic cylinder 31 is connected between the main frame 14 and each bell crank lever 27 whereby the relative height of the main frame 14 can be adjusted by altering the relative positions of the bell crank levers 27, the arm 28 and the associated rear and front wheels 21 and 23. Movement of the main frame 14 is effected by a draught frame 16 connected to the prime mover. The draught frame I β comprises two rearwardly extending, diverging legs 32 attached by locating pins 33 to substantially parallel, depending sections 34 which are interconnected by a transverse tubular member 36. The draught frame 16 is connected to the main frame 14 by two pairs of arms 38, 39 pivotally mounted to the depending sections 34 and the main frame 14. The front arm 38 of each pair is of an inverted Y configuration. The upper part of each front arm 38 is connected to the respective depending section 34 by a transverse pivot pin 41 while the lower parts of the front arms 38 are pivotally mounted to the main frame 14 by spaced, coaxial transverse pivot pins 42 and 43. The rearmost arm 39 of each pair is pivotally mounted to the respective depending sections 34 and the main frame 14 by additional pivot pins 44, 45 which extend substantially parallel to the pins 41, 42 and 43. The mounting of the respective arms 38, 39 and the location of the respective mounting pins results in a line containing the axes of the pivotal connection of one arm 38 intersecting a line containing the axes of the pivotal connection of the other arm 39 at a point which is instantaneously located at 47 (see Figures 4 to 6) and which is preferably at or near the ground surface 49. This point 47 comprises a virtual hinge point about which the arms 38, 39 instantaneously pivot and which, therefore, the draught forces and the resistant forces act. When a draught force is applied to the draught frame 16 in the forward moving direction, the arm arrange¬ ment causes the main frame 14 to act as if it were flexibly connected to the draught frame 16 by a hinge located at the instantaneous virtual hinge point 47. By appropriate dimensioning and angulation of the arms 38 and 39, the instantaneous virtual hinge point 47 may be caused to lie at a desired plane on or beneath the ground surface 49, preferably at the plane of the resultant soil resistant forces acting upon the tines 22. By locating the instant- aneous virtual hinge point 47 on this plane, the resultant rotative moment of the working frame is virtually eliminated and the cultivator 12 acts as though it is being drawn by draught forces acting through the instantaneous virtual hinge.point 47. Referring to Figures 4 to 6, by having front wheels 23 and rear wheels 21, the main frame 14, and any attached side frames 15, are able to follow soil undulations without significant changes in depth of penetration between tines 22 at the front and rear of the main frame 14. This, therefore, enables very accurate control of the depth of penetration of the cultivator tines 22 which is vitally important in tillage and sowing operations, particularly with new varieties of grains which have been recently developed and which must be sown at precise depths to provide optimum development. As will be seen in Figure 4, when the cultivator 12 is being drawn across level ground, the virtual hinge point 47 is at or near the depth of penetration of the tines 22. On rising ground, as shown in Figure 5, the relative movement between the draught frame 16 and the main frame 14 causes relative movement of the arms 38 and 39 which varies the location of the instantaneous virtual hinge point 47 whilst maintaining the substantially constant depth of penetration of the tines 22. Similarly, as shown in Figure 6, when the ground falls away in front.of the cultivator 12, the instantaneous virtual hinge point 47 moves rearwardly due to relative movement of the draught frame 16 and the main frame 14 causing relative movement of the pairs of arms 38 and 39. This relative movement enables the depth of penetration to be maintained substantially constant- It will be seen from Figures 1 and 2 that the pairs of arms 38 and 39 are supported in a cantilever fashion from the depending sections 34. A pair of hydraulic cylinders 51 mounted to the rear end of the main frame 14 each have a forwardly extending piston rod 52 the front end of which is carried in a lost motion slot 53. Actuation of the hydraulic cylinders 51 pivots the main frame 14 to the position illustrated in dashed lines in Figure 3 whereby the working tools i.e. the cultivator tines 22, are lifted from the ground for transportation. The position of the pairs of arms 38 and 39 relative to the depending ' sections 34 facilitates the relative movement of the main frame 14 to the position shown. Referring to Figure 7 there is shown a modified form of:>•cultivator in accordance with the present invention. In this embodiment, a curved guide 55 is mounted on the main frame 14, the curvature of the guide preferably being arcuate with a radius "R". The draught frame 16 carries at the rear end of the depending section 34 a pair of front rollers 56 which engage the front surface of the curved guide 55, and a rear roller 57 to engage a rear guide surface 58. The instantaneous centre of the front rollers 56 and rear roller 57 on the curved guide 55 becomes the point through which the draught forces are effectively applied to the main frame 14. This point is located on or close to the centre of curvature of the curved guide 55 or, if the curved guide is not arcuate, at the instantaneous centre of that part contacted by the rear roller 57. By appropriate design of the guide 55 and location of the rollers 56, 57, the instantaneous centre through which the draught and resistance forces act can be located on or adjacent the load plane. It will be appreciated that as the relative positions of the draught frame 16 and the main frame 14 changes due to variation in topography, the rollers 56, 57 move along the curved guide 55 maintaining the instantaneous load point at the desired location.

Claims: 1. A draught frame structure comprising a draw bar means having a front end to be connected to a prime mover, equipment frame means supported on wheels, and first and second load transfer parts to transfer draught and resistance forces between the draw bar means and the equipment frame means, said first and second load transfer parts interacting to define an instantaneous centre through which the resultant of the draught and resistance forces act. 2. A draught frame structure according to claim 1 wherein said first and second load transfer parts comprise a pair of longitudinally spaced arms one end of each of which is pivotally connected to the draw bar means and the other end of each of which is pivotally connected to the frame means, the pivotal connection axis extending transversely and being so located that lines passing through the respective connections for each arm intersect at or adjacent the horizontal plane along which the resistance forces act. 3. A draught frame structure according to claim 1 or claim 2 wherein the equipment frame means comprises an agricultural implement having a working frame carrying soil working tools. 4. A draught frame structure according to claim 1 wherein said draw bar means comprises a pair of legs defining an A-frame, the apex of which is adapted. to be connected to the prime mover and the free ends of the legs having upwardly and rearwardly extending rear portions overlying and connected to the frame means by separate connection means, each connection means including two, longitudinally spaced arms upper ends qf which are pivoted about transverse axes to the respective leg portion and lower ends of which are pivoted about transverse axes to the frame means, the pivot connections of the arms connected to one leg being substantially coaxial with those of the other pair of arms and being so located that a plane containing the pivotal axes of one arm and a plane containing the pivotal axes of the other arm of the respect¬ ive pair intersect below the frame means. 5. A draught frame structure according to claim 4 wherein the upwardly and rearwardly extending rear leg portions of the A-frame are substantially parallel. 6. A draught frame structure according to claim 4 or claim ' 5 wherein the respective pairs of arms are pivotally connected to a front part of the frame means. 7. A draught frame structure according to claim 1 wherein said first and second load transfer parts comprise a curved track member mounted on either the draw bar and frame means and interacting roller means mounted on the other, the curved track means having an instantaneous centre at or adjacent the plane along which the resistance forces act and the roller means transmitting draught forces in the direction of the instantaneous radius of said curved track corresponding to the roller means position. 8. A draught frame structure according to claim 7 wherein said draw bar means includes two, laterally spaced draught frame members and said load transfer parts include a track member and associated roller means for each draught frame member. 9. An agricultural implement comprising a main frame carrying ground working tools, wheels supporting the main frame above the ground, a draw bar to connect the main frame-to a prime mover, the draw bar having two legs diverging rearwardly from the front thereof and terminating in spaced, substantially parallel rear end portions over¬ lying a front part of the main frame, a pair of front links connected by transverse-pivots to the respective rear end portions and the main frame, the front links extending downwardly and rearwardly from the rear end portions of the draw bar legs, a rear link longitudinally spaced from each respective front link and connected by transverse pivots to the respective rear end portions and the main frame, the rear links extending downwardly and forwardly from the rear end portions. 10. An implement according to claim 9 wherein lines connecting the pivots of each pair of front and rear links intersects at or adjacent ground level. 11. An implement according to claim 9 or claim 10 wherein said ground working tools comprise cultivator or plough shares. 12. An implement according to any one of claims 9 to 11 wherein said main frame is supported by front and rear wheels which are mounted on pivotal supports enabling the height of the main frame to be adjusted. 13. An implement according to any one of claims 9 to 12 wherein each said front link is of an inverted "Y" shape, and the pivotal connection to the main frame comprises spaced coaxial pivot pins for each part of the link. 14. An implement according to any one of claims 9 to 13 wherein said links are mounted by cantilevered pivot pins extending from the rear end portions and the main frame, whereby the main frame can move from its normal, substantially horizontal operating position to an elevated position whereby the ground working tools are supported above the ground. 15. An implement according to any one of claims 9 to 14 wherein said substantially parallel .rear end portions are interconnected by a transverse tubular member disposed in front of the main frame, and the draw bar legs are connected to the rear end portions by a pair of locating pins. 16. An implement according _to any one of claims 9 to 15 wherein secondary frames are hinged to either side of the main frame. 17. A cultivator comprising a wheeled main frame carrying cultivator tines, height adjustment means to adjust the height of the frame, a draw bar comprising a pair of rearwardly extending diverging legs, a draw frame connected to the rear ends of the legs and including two spaced substantially parallel frame members, a pair of longitu- dinally spaced arms extending downwardly from each frame member, the arms of each pair being connected to the respective frame member by pivot means permitting relative longitudinal movement, the lower ends of the arms being pivoted to the main frame, and the arms of each pair instantaneously defining an angle the apex of which is on or adjacent the ground surface. 18. A cultivator according to claim 17 wherein the length of each arm is fixed. 19. A cultivator substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: REMPE HENDRIK, REMPE, HENDRIK
Applicants: ALFARM IND, ALFARM INDUSTRIES PTY. LTD.
Application year: 1986
Main classification: A01B59
IPC codes: A01B23, A01B35, A01B59, A01B73