COUPLING HOOK PARTICULARLY FOR THE LOWER ARMS OF A THREE-POINT LINKAGE OF A TRACTOR

Abstract: The invention relates to a coupling hook particularly for the lower arms of a three-point linkage of a tractor, which is intended to attach an implement to a tractor by means of a coupling ball (11) or similar. The coupling hook includes a body (1), in which there is a housing (25) and a coupling jaw (27) and a catch (2) moving linearly in guides (13, 23) of housing (25) and opening at a downward angle. In addition, the coupling hook includes a spring (8) pressing catch (2) into the retaining position and an operating lever (3) for moving catch (2). According to the invention, operating lever (3) operating the coupling hook from above, is connected to catch (2) by means of a pull-turning device (26). Pull-turning device (26) is arranged to turn the operating lever's (3) pulling movement, which is directed essentially upwards, into a movement of the catch (2) from the retaining position to the open position.

Description: COUPLING HOOK PARTICULARLY FOR THE LOWER ARMS OF A THREE-POINT LINKAGE OF A TRACTOR The present invention relates particularly to a coupling hook for the lower arms of a three-point linkage of a tractor, which coupling hook is of the type referred to in the preamble of Claim 1 Snap-fit couplings of three-point linkages for tractors have been developed for a long time. Generally, coupling balls, to which the tractor's upper and lower arms are connected, installed on the device to be coupled, are used in quick-action couplings. The ends of the upper and lower arms have special coupling hooks for this quick-action coupling. DE publication number 27 49 311 discloses a coupling hook for the lower arms, in which there is a convention coupling jaw for a coupling ball. The coupling hook includes a catch moving in a drilled hole machined in the body of the hook for locking the coupling ball to the coupling jaw. A cable is connected to the catch for pulling the catch into the open position, i.e. inside the body. In addition, the coupling hook includes a spring, which is arranged to press the catch the whole time into the locking position. However, the catch and the spring are, as known, arranged in such a way that the coupling hook can be coupled to the coupling ball while the catch is in the locking position. In coupling, the coupling ball pushes the catch in front of it inside, which, when the coupling ball settles into the coupling jaw, rises immediately to the locking position and forms the coupling. In the solution described above, the catch is pulled by means of a long cable, which stretches in use and demands continual maintenance. In addition, the cable must be installed under the lower arm, where it is continually exposed to external impacts. The separate operating lever is also easily broken and requires a great deal of space for installation. In addition, in the solution, both catches are arranged to be operated simultaneously by a single operating lever. This prevents the catches being used separately. The present invention is intended to create a new type of mechanism especially for the coupling hook of the lower arm of a three-point linkage of a tractor, which is reliable and which is easy and natural to use. The characteristic features of a coupling hook according to the invention are disclosed in the accompanying Claims. A coupling hook according to the invention differs from known coupling hooks particularly in that not only is the movement of the catch optimal, but the movement and location of the operating lever are also optimal. This is achieved by turning the movement of the operating lever to become the movement of the catch, by means of a special pull- turning device. The reliability of the operation of a catch to be applied in the coupling hook has been tested in a lower arm coupling hook, which is disclosed, for example in FI publication 100845 and DE publication 28 31 862. The utilization of such a catch in the coupling hook of a lower arm is possible only now, with the aid of a pull-turning device according to the invention. The directions of movement of both the catch and the operating lever are thus optimal, because they can be selected freely, entirely independently of one another. The operating lever is preferably above the hook, where it is protected from external impacts. The direction of movement of the operating lever is also optimal, i.e. at a slight upward angle. In practical embodiments, the angle between the direction of movement of the operating lever turned by the pull-turning device and that of the catch is about 90°. In addition to the pull-turning device, it is possible, according to the invention, to create large working surfaces in the catch, thus giving it excellent resistance to wear. It is also simple to combine the operation of the coupling hooks, without complicated accessories. In the following, the invention is disclosed in detail with reference to the accompanying drawings of one embodiment of the invention, in which Figure 1 shows the coupling ball of a coupling hook according to the invention locked to the coupling jaw, Figure 2 shows the coupling hook in Figure 1 locked in the open position, Figure 3 shows another embodiment of a coupling hook according to the invention in the same position as in Figure 1, Figure 4 shows the coupling hook in Figure 3 pulled into the open position, Figure 5 shows a third embodiment of a coupling hook according to the invention in the same position as in Figure 1, and Figure 6 shows the coupling hook in Figure 5 pulled into the open position. In the figures, the coupling hook according to the invention is shown without the cover that is welded onto the coupling hook in the final product. The shaded area depicts the surface 31 of the body 1 of the coupling hook, over which the cover extends. The cover conforms to the outer shape of the coupling hook and also lies in the bevel 32 in the coupling hook, while nevertheless leaving the lower part of the catch mechanism visible. This opening is mainly intended to allow impurities that enter the coupling hook to fall out by gravity. In Figures 1 and 2, the edge of the cover forming the opening is shown by a broken line. The coupling hook itself too is welded to the lower arm 29. The coupling hook includes a coupling jaw 27 and a housing 25. Coupling jaw 27 is conventional and is particularly adapted to receive coupling ball 11. Usually, the coupling ball is permanently attached to the implement to be coupled, or else it is installed on a normal three-point linkage pin. The snap-cou- pling as such can be made without even a coupling ball, but this is not, however, recommended. In addition, the coupling ball helps to eliminate small differences of angle between the pin and the lower arm. In the figures, the coupling ball is shown with the reference number 11 and its surface with the reference number 24. Housing 25 is machined in the forged coupling housing, and catch 2 with its operating mechanism is then fitted to it. Catch 2 is supported from all sides at least to some extent by the coupling jaw. Edges 13 and 23, out of the opening formed by which catch 2 emerges from housing 25, act as the actual load- bearing guides. In the embodiment in Figure 1, edge 13, which is above pawl 5, extends over the width of catch 2 for the entire length of its movement, even if there is a slot in edge 13 arranged at operating lever 3 on top of catch 2. In this case, a large load-bearing surface is formed, which substantially reduces wear in the counter-surfaces. Due to edges 13 and 23, the movement of catch 2 is linear. Catch 2 also has a slot 9, in which there is a pin 7 set in body 1, arranged to limit the linear movement of catch 2. Besides guiding catch 2, pin 7 also limits the linear movement of catch 2 to its operating area and prevents the operating mechanism of catch 2 from being loaded unnecessarily. Without pin 7, the force of spring 8 set in catch 2 would be transmitted to the entire operating mechanism. Spring 8 is fitted into hole 19 drilled in the lower end of catch 2 and continuously presses catch 2 into the locked position. The other end of spring 8 lies in a hole 30 machined in the base of housing 25. In Figures 1, 3, and 5, the coupling hook is shown in the retaining position, in which catch 2 protrudes from housing 25 to lie partly on top of coupling ball 11. A position even partly on top of the ball prevents the coupling from disconnecting, because coupling ball 11 can only rise out of the coupling jaw 27 parallel to its centre line, in this case, straight upwards. Thus, catch 2 locks coupling ball 11 firmly into coupling jaw 27. In the retaining position, there is only a small tolerance between the surface 24 of coupling ball 11 and the locking surface 20 of catch 2, because no tolerance at all is required for catch 2 to open. After this small toler- ance, the forces acting on locking surface 20 are transmitted almost entirely through the counter-surface 14 of the opposite side of catch 2 to the edge surface 13 above the opening, especially in the area of their upper sections. Thus, none of the forces transmitted from the coupling ball 11 can open catch 2. Instead they tend to force catch 2 into the retaining position, in the same way as spring 8. It is mostly only during coupling that the lower surface 10 of catch 2 lies next to edge 23. Locking surface 20 of catch 2 is preferably a spherical surface, corresponding to the curvature of coupling ball 11. Locking surface 20 then becomes as large as possible, which reduces wear in catch 2. In the same way, coupling ball 11 is better centred in coupling jaw 27. The end, i.e. opening sur- face 12 of catch 2 is flat, which, during coupling, helps coupling ball 11 to settle into the coupling jaw, when catch 2 is in the retaining position. The coupling ball 11 pushes catch 2 in front of it inwards, the catch rising once again into the retaining position, once coupling ball 11 has settled into coupling jaw 27. The coupling hook also includes operating lever 3 set in opening 28 above housing 25 for locking catch 2. In this case, operating lever 3 is made from a sheet material. According to the present invention, operating lever 3 is connected to catch 2 by means of pull-turning device 26, which is arranged to turn the essentially upwards-directed pulling movement into the movement of catch 2 from the retaining position to the open position. Thanks to pull-turning device 26, it is possible to locate operating lever 3 above the coupling hook, which is a significant advantage in terms of its operation. Operating lever 3 is also protected inside the coupling jaw while the lower surface of the coupling jaw is closed and smooth. In addition, the upper end of operating lever 3 is dimensioned so that, in the retaining position, the aforesaid upper end covers opening 28 of housing 25, as shown in Figures 1, 3, and 5. A handle 18 is also fitted to the upper end, to make is easier to grip operating lever 3. The angle between the pulling movement of operating lever 3, turned with pull-turning device 26, and catch 2 is 70° - 110°, preferably 80° - 100°. The angle between catch 2 and coupling ball 11 is preferably, as in the embodiments disclosed, about 50°. In that case, catch 2 opens at a downward angle, while operating lever 3 points slightly upwards. In general, this is an optimal arrangement from the points of view of the catch and operating lever. A pull-turning device according to the invention can be implemented in different ways. One embodiment is shown in Figures 1 and 2. In it, the pull-turning device 26 includes a pawl 5 mounted to turn in bearings in housing 25. Pawl 5 allows movements in different directions to be easily combined. In the embodiment, pawl 5 is secured to the body 1 of housing 25 by means of an axle pin 4, around which pawl 5 rotates. In addi- tion, pawl 5 is set to engage with the corresponding teeth 15 arranged in catch 2. Pawl 5 also prevents catch 2 from turning downward. Pawl 5 also preferably includes a lever arm 17, to which operating lever 3 is jointed, to rotate pawl 5. In this case too, joint 6 is formed simply by a pin and an opening in operating lever 3. A good moment ratio for lever arm 17 has been found to be 1,1 - 2,0, preferably 1,3 - 1,7. Lever arm 17 allows a reduction in the force required to operate catch 2. Spring 8 can then be dimensioned to be sufficiently stiff to hold catch 2 closed, without affecting the operating comfort of the coupling hook. In the first embodiment disclosed, pawl 5 is located beneath catch 2. This permits a large angle of rotation in pull-turning device 26 and also a sufficient movement in catch 2, without being limited by lever arm 17. Alternatively, pull-turning device 26 can be above catch 2, though in this case the advantages referred to are lost. Because pawl 5 never makes a complete revolution, pawl 5 only has teeth 16 over a certain segment. The angle subtended by the arc of the segment is 60° - 120°, preferably 90° - 110°. Generally, pawl 5 is arranged in such a way that it is always engaged with the teeth 15 of catch 2. The limited arc of the circle has 3 - 9 teeth 16, preferably 4 - 6, which is sufficient to achieve rotation. At the same time, the teeth should be made sufficiently large. Preferably, the teeth 16 are straight, so that they are easily manufactured and do not unnecessarily load the catch mechanism. In the embodiment, the tooth engaged in the retaining position is higher than the others. Correspondingly, the teeth 15 at the bottom end of catch 2 extend of the entire width of catch 2. This construction ensures the durability of the tooth that must transmit the force by itself when the teeth begin to disengage. In the centre, catch 2 is narrowed, which permits operating lever 3 and catch 2 to move side by side. In addition, pawl 5, or catch 2, or both are precision-cast pieces. Thus, they have excellent precision of shape, surface quality, and resistance to wear. Figure 2 shows the coupling hook of Figure 1 in the open position. In this case, catch 2 is pulled into housing 25, to permit coupling ball 11 to rise out of coupling jaw 27. Catch 2 can also be locked into the open position, by simply setting operating lever 3 to rest its dog 22 on pin 21 in body 1, according to Figure 2. Pull-turning device 26 can be implemented in many other ways than the above, though the toothed segment described has proven to be extremely practical in tests. In the most preferred mechanism, there is at least one member mounted by bearings in the housing, in which there are opposing support points for bearings on other sides, so that it can turn the direction of movement. In place of the toothed segment, it is possible to use a jointed arm, which is also jointed to the catch. In the embodiment, the pull-turning device is jointed to the housing by means of a pin. A form of jointing that, as such, is practicable can be implemented by means of circumferential surfaces. A small amount of movement in the pull-turning device can also be incorporated in a joint of this kind. The operating principle disclosed in the section above is also applied in a second embodiment of the coupling hook, shown in Figures 3 and 4. In this case, the pull-turning device 26 includes an intermediate piece 33, mounted by bearings in catch 2 so that it can rotate, which is joined to catch 2 by means of jointed arm 34. The bearings of intermediate piece 33 are implemented by means of an axle pin 4 fitted to body 1. Inter- mediate piece 33 too includes a lever arm 17', to which operating lever 3 is jointed to rotate intermediate piece 33. Because intermediate piece 33 is smaller that pawl 5, it is possible to make lever arm 17' long. The moment ratio created by lever arm 17' is then also greater. Generally, the moment ratio is 1,0 - 2,4, preferably 1,5 - 2,0. This embodiment has the same main features and the same reference numbers are used for the same functional components. However, this embodiment has two significant special features. Intermediate piece 33 of the pull-turning device and part of jointed arm 34 are set above catch 2. This allows housing 25 to be made smaller and body 1 correspondingly stronger. In addition slot 9 of catch 2 is curved in such a way that the bottom end of catch 2 is arranged to turn downwards when catch 2 is pulled from the retaining position to the open position. At the same time, intermediate piece 33 presses catch 2 downwards at point 35 at the beginning of the opening pull. This makes it easier to open catch 2 when coupling ball 11 is loading the catch. The aforementioned features do not, however, affect the grip of the coupling hook. In addition, the movement of catch 2 is still essentially linear, despite the small initial turn. The components of the second embodiment are smaller and easier to manufacture than the components of the first embodiment. Though the second embodiment has several joints on account of jointed arm 34, wear in them does not affect the grip of the coupling hook. This is because the line of movement of catch 2 is determined by edges 13 and 23 and slot 9 and pin 7 jointly. Figures 5 and 6 show a third embodiment of the coupling hook. Its operating principle corresponds to the embodiment disclosed above. Here too pull-turning device 26 includes an intermediate piece 33' that is mounted in bearings to rotate in housing 25. However, intermediate piece 33' operates catch 2 directly through dog 36, which reduces the number of components in the pull-turning device. In catch 2, there is also a notch 36', corresponding to dog 36. In this case, dog 36 and notch 36' together form in principle a single-tooth gear. The moment ratio created by lever arm 17' in intermediate piece 33' corresponds essentially to the moment ratio of the second embodi- ment. In addition, the third embodiment has significant special features. The bottom end of catch 2 has a shaped surface 9', which pin 7 follows to determine the line of movement of catch 2. In the retaining position shown in Figure 5, pin 7 lies in hole 37 in catch 2. In this position, even the turning of coupling ball 11 cannot open the catch, because catch 2 cannot turn when upper surface 14 presses against upper edge 13. On the other hand, catch 2 is easily opened by puling on operating lever 3. Also when locking coupling ball 11 catch 2 can be pressed slightly downwards, when pin 7 lies on the straight section of surface 9', making it possible to press catch 2 downwards. In addition, intermediate piece 33' of the pull- turning device and catch 2 are shaped to create a two-stage movement in catch 2. First of all, catch 2 is forced by inter- mediate piece 33' to turn slightly, after which it moves essentially linearly downwards, as in the second embodiment. For this purpose, there is a dog 38 in intermediate piece 33', which, at the start of the down pull, presses catch 2 down at point 35. The actual movement of the catch then takes place through the joint operation of dog 36 and notch 36' ■ The reduced number of components allows intermediate piece 33' to located higher and pin 7 correspondingly lower in housing 25 than previously. This evens the line of movement of the catch and makes it possible to manufacture a strong catch. In addition, spring 8 can be located in curve under catch 2, when the spring will also always press the catch against the upper edge. In addition, intermediate piece 33' is jointed to operating lever 3 by means of slot 39. Thus, when the coupling ball is being locked, the operating lever hardly moves and the housing remains closed. In the locking position, there is also a hole 40 through the coupling hook at the upper part of slot 39, in which a locking pin (not shown) can be placed. Joint pin 6, which links intermediate piece 33' and the operating lever is located in the same hole. The movement of the entire pull- turning device can be prevented by means of the locking pin. This makes it possible to lock the operation of the coupling hook, which improves work safety, among other things. The coupling hook can be dismantled and the components replaced, even though the cover is welded onto it. Assembling is also possible without opening the cover. If the pins are removed in a certain order, the entire catch mechanism can be dismantled. The coupling hook disclosed here and other embodiments of the coupling hook according to the invention have in common an operationally jointed pull-turning device, in which there are lever arms or similar to achieve moment conversion.

Claims: Patent Claims 1. A coupling hook particularly for the lower arms of a three- point linkage of a tractor, which is intended to attach an implement to a tractor by means of a coupling ball (11) or similar, which coupling hook includes a body (1), in which there is a housing (25) for a catch mechanism and a coupling jaw (27), especially arranged to receive the aforesaid coupling ball (11), the movement of which in relation to the coupling hook is essentially vertical; a catch (2) moving essentially linearly in guides (13, 23) arranged in the housing (25) and opening downwards; a spring (8) arranged to press the catch (2) into the retaining position, in which retaining position the end of the catch (2) protrudes from the housing (25) towards the coupling jaw (27) at least partly on top of the coupling ball (11) to lock the coupling ball (11) into the coupling jaw (27), whereas in the open position catch (2) is withdrawn into the housing (25) , permitting the coupling ball (11) to rise out of the coupling jaw (27) ; and an operating lever (3) fitted to catch (2) particularly to move catch (2) from the retaining position to the open position, characterized in that the operating lever (3) operating the coupling hook from above, fitted in as such a known manner to the opening (28) above the housing (25) , is connected to the catch (2) by means of a pull-turning device (26), which is arranged to turn the operating lever's (3) pulling movement that is directed essentially upwards into a movement of the catch (2) from the retaining position to the open position. 2. A coupling hook according to Claim 1, characterized in that the angle between the pulling movement of operating lever (3) that is turned by the pull-turning device (26) and the movement of catch (2) is 70° - 110°, most preferably 80° - 100°. 3. A coupling hook according to Claim 1 or 2, characterized in that the pull-turning device (26) includes a pawl (5) mounted in bearings to rotate in housing (25), which is arranged to engage corresponding teeth (15) set in the catch (2) 4. A coupling hook according to Claim 3, characterized in that the pawl (5) includes a lever arm (17), to which operating lever (3) is jointed to rotate pawl (5), the moment ratio created being 1,1 - 2,0, most preferably 1,3 - 1,7. 5. A coupling hook according to Claim 3 or 4, characterized in that pawl (5) is located beneath the catch (2), in which case operating lever (3) extends above over catch (2) to pawl (5) beneath. 6. A coupling hook according to one of Claims 3 - 5, charac- terized in that pawl (5) has teeth (16) only for an arc of the circle, which arc of the circle subtends an angle of 60° - 120°, most preferably 90° - 110°. 7. A coupling hook according to Claim 6, characterized in that teeth (16) are straight and that there are 3 - 9, most preferably 4 - 6, of them. 8. A coupling hook according to Claim 1 or 2, characterized in that pull-turning device (26) includes an intermediate piece (33) mounted to rotate in bearings in housing (25), and which is connected to catch (2) by means of jointed arm (34). 9. A coupling hook according to Claim 1 or 2, characterized in that pull-turning device (26) includes an intermediate piece (33') mounted to rotate in bearings in housing (25) and which includes a dog (36) and that the catch includes a notch (36') corresponding to dog (36) , in which case intermediate piece (33') is arranged to move catch (2) with the aid of dog (36). 10. A coupling hook according to Claim 9, characterized in that intermediate piece (33') is jointed to operating lever (3) by means of a slot (39) . 5 11. A coupling hook according to Claim 10, characterized in that, in the locking position, there is a hole (40) through the coupling hook at the upper part of slot (39) , to allow a locking pin to be placed in the slot. 10 12. A coupling hook according to Claim 8 or 9, characterized in that intermediate piece (33) includes a lever arm (17'), to which operating lever (3) is jointed to turn intermediate piece (33, 33'), the moment ration created being 1,0 - 2,4, most preferably 1,5 - 2,0. 15 13. A coupling hook according to Claim 8 or 9, characterized in that intermediate piece (33, 33') and part of jointed arm (34) are located above catch (2) . 20 14. A coupling hook according to one of Claims 1 - 13, characterized in that there is a slot (9) or surface (9') in the catch (2) and a pin (7) in body (1) fitting this, which is arranged to limit the linear movement of catch (2). 25 15. A coupling hook according to Claim 14, characterized in that surface (9') forms a hole (37) at the bottom end of catch (2), into which pin (7) is arranged to engage when catch (2) is in the retaining position. 30 16. A coupling hook according to one of Claims 1 - 15, characterized in that the upper end of operating lever (3) is dimensioned in such a way that, when catch (2) is in the retaining position, the aforesaid upper end covers the upper opening (28) in housing (25). 35 17. A coupling hook according to Claim 14, characterized in that slot (9) in catch (2) is curved in such a way that the bottom end of catch (2) is arranged to turn downwards, when catch (2) is pulled from the retaining position to the open 5 position. 18. A coupling hook according to one of Claims 1 - 17, characterized in that catch (2) is a precision-cast piece. 10 19. A coupling hook according to one of Claims 3 - 7, characterized in that pawl (5) is a precision-cast piece.

Inventors: VIIKKI PAAVO, VIIKKI, PAAVO
Applicants: VIIKKI PAAVO, VIIKKI, PAAVO
Application year: 1999
Main classification: A01B59
IPC codes: A01B59