AU760047B2 - Coupling device - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT C 4.

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Name of Applicant: Actual Inventor: Address for Service: Invention Title: P H RURAL LIMITED BARRY KEITH McFARLANE CULLEN CO., Patent Trade Mark Attorneys, 239 George Street, Brisbane, Qld. 4000, Australia.

COUPLING DEVICE Details of Associated Provisional Application: No. PP9909 filed 21 April 1999 The following statement is a full description of this invention, including the best method of performing it known to us: 2 COUPLING DEVICE BACKGROUND OF THE INVENTION This invention relates to coupling devices and in particular to devices for coupling the shank of an implement to be towed to the tool bar of the towing vehicle. The invention has particular applicability to the towing of agricultural implements and will be described primarily with that use in mind. It will nevertheless, be readily appreciated by the skilled addressee that the invention has much broader ramifications and uses beyond the agricultural use described.

Coupling devices for agricultural implements 15 invariably incorporate a sacrificial element to prevent structural damage to the implement should it collide with 0 an obstacle. There are essentially two versions of such S coupling devices. The first includes a holder for holding the shank in a downward extending orientation and 20 a connector for connecting the holder to the rear side of .the tool bar. The holder is hinged to the connector about a horizontal hinge axis at the respective upper oofe ends of the holder and connector. The connector has a pair of spaced cantilever arms which extend horizontally rearwards on two opposite sides of the shank, below the holder. Each arm has a hole at its free end. A sacrificial bolt extends between the arms and is received in the holes. The sacrificial bolt is disposed rearwardly of the shank with the shank abutting against it.

In use, when the shank encounters an obstacle, preventing the towed implement from proceeding without damage, the lower end of the shank is forced rearwardly causing the holder to rotate about the hinge axis relative to the connector. This, in turn, causes the lower end of the shank to move rearwards and shear the sacrificial bolt.

3 A problem with this type of coupling device is that there is usually a gap between each side of the shank and the respective arm on that side. Thus, when the shank exerts a force on the sacrificial bolt, the bolt tends to bend before shearing. Furthermore, the sacrificial bolt also causes enlargement and deformation of the holes in the arms, resulting in a loose fitting between the shank and the sacrificial bolt. This causes the shank to clatter against the sacrificial bolt and further exacerbate the bending of the sacrificial bolt and the enlargement and deformation of the holes.

o: Consequently, the sacrificial bolt does not shear cleanly, and the remaining parts often have burrs. The 15 result is that the repair and maintenance of the coupling device can be impaired.

o*o* The second type of coupling device in common use also includes a holder for holding the shank in a 20 downwardly extending orientation and a connector for connecting the holder to the tool bar. In this case also, the holder is hinged to the connector about a 0horizontal hinge axis, located at the upper respective 0 ends of the holder and connector. At their lower ends, the holder and connector each have a flange with an aperture therein, the flanges being parallel and abutting each other. A sacrificial headed bolt extends through holes in the flanges and is tightened in place by a nut screwed onto a threaded end of the bolt. The sacrificial bolt thus holds the flanges together.

As in the previous coupling device, when the shank encounters an obstacle preventing the towed implement from proceeding without damage, its lower end is forced rearwardly which causes the holder to rotate relative to the connector about the hinge axis. This forces the flanges apart and a longitudinal force is exerted on the sacrificial bolt, which then fails either ,i 4 by the head being pulled off, or by the nut being stripped off.

A variation on this type of coupling device has a nut at each end of the sacrificial bolt instead of a nut and a head. In certain cases the nuts have been half-nuts and in other cases the nuts have been threequarter nuts, for reducing the force required to strip the nuts off the bolts.

A problem with this type of coupling device is that the force required to cause the sacrificial bolt to fail is not precisely known. Furthermore, once the sacrificial bolt has failed, to replace it requires a new 15 bolt to be inserted through the holes and a nut or nuts to be screwed onto the bolt. This is time consuming and means that a tool must be carried at all times for this S* purpose.

OBJECT OF THE INVENTION It is therefore an object of the invention to provide a coupling device which obviates the aforementioned disadvantages or at least provides the public with a useful alternative.

SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a coupling device for coupling a shank of an implement to be towed to the tool bar of a draft vehicle, said coupling device comprising a connector plate and a shank holder, said shank holder being connected to said connector plate by a hinged connection, said connector plate including two ledges projecting from a face thereof to accommodate a protrusion on the shank holder, wherein said ledges and said protrusion are joined together by a sacrificial pin, the construction and arrangement being such that when the shank contacts an obstacle hindering its movement in a towing direction, the shank causes the holder to rotate about its hinged connection and the sacrificial pin to shear as the protrusion on the holder is forced away from the ledges on the connecting plate.

DETAILED DESCRIPTION OF THE INVENTION The ledges projecting from the connector plate are preferably designed to project perpendicular to the plate and parallel with one another. In such a design, the protrusion on the shank holder will be configured to snugly fit between the ledges and be held firmly in situ by means of a headed sacrificial pin extending through aligned passageways in the ledges and the protrusion.

15 Shearing of the sacrificial pin occurs by virtue of the protrusion on the shank moving laterally with respect to the ledges on the connector.

Preferably, the hinged connector has a hinge 20 axis which is substantially horizontal in use. In this case, the hinged connector is preferably formed at the upper, in use, vertical extremity of the holder and the ledges are spaced vertically therefrom toward the lower, in use, end of the connector plate.

The aligned passageways in the ledges and in the protrusion, in such a preferred arrangement, will be essentially vertical when the shank holder is in an operative position. Suitably, the passageways in the ledges which open out, respectively, to the top and bottom of the device, are enlarged so as to accommodate the head of the sacrificial pin.

In a preferred embodiment the connector plate includes a pair of cantilever arms extending on opposite sides of the shank holder for providing lateral support to the shank holder.

6 In a preferred embodiment the shank holder defines a shank passage for accommodating the shank, the shank passage having an inner surface defining a longitudinal recess for accommodating position-marking ribs forming part of the shank holder.

The coupling device can be connected to the tool bar of a towing vehicle by means of bolts which can be inserted through aligned apertures in the connector plate and in the tool bar.

According to a second aspect of the present invention there is provided a coupling device for S. coupling a shank of an implement to the tool bar of a 15 draft vehicle, said coupling device including a connector for mounting to the tool bar, and a shank holder body being hingedly mounted to the connector for movement S- between an operative and a released position wherein the holder body, in the operative position, maintains the shank in a downwardly extending orientation; wherein there is a first wall associated with the holder body which includes a first opening therein; a second wall associated with the connector and including a second opening therein whereby, in the operative position of the holder body, the first wall and the second wall are substantially parallel and abut one another and the first opening and the second opening are aligned to receive a common sacrificial pin, and wherein hinging of the body out of the operative position and into a released position causes the first wall to slidably progress relative to the second wall to bring the first opening and the second opening out of alignment to shear the pin.

Preferably the holder body includes a protrusion and two first walls, each first wall being associated with the holder body by being an upper and lower wall, respectively, of the protrusion, and the connector includes a pair of spaced ledges and two second walls, each second wall being associated with the connector by being a wall of a respective one of said ledges, the second walls facing each other and defining a gap between them, the protrusion being received in the gap, with each first wall facing and abutting a respective one of said second walls when the holder body is in the operative position.

DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view, with hidden structure shown in phantom outline, of a coupling device according to one aspect of the present invention; and o 15 Figure 2 is a plan view of the coupling device of Figure 1, also showing hidden structure in phantom outline.

DESCRIPTION OF PREFERRED EMBODIMENTS 20 Preferred embodiments of the invention will now be described with reference to the drawings, in each of which like reference numerals refer to like parts.

Referring to both drawings simultaneously, the coupling device 1 is for mounting onto a tool bar of a draft vehicle such as a tractor (not illustrated). The coupling device 1 includes a shank holder 2 for holding a shank 3 in a vertically extending orientation. The coupling device 1 also includes connector element 4. The connector element 4 is for connecting the shank holder 2 to the tool bar. The shank holder 2 is hingedly connected to the connector element 4 by a hinge pin Shank holder 2 has a protrusion 6 which incorporates a vertical holder passage 7. Passage 7 has openings 8 and 9 through upper and lower faces 10 and 11, respectively.

The connector element 4 has a pair of spaced ledges 12 and 13. Ledges 12 and 13 have faces 14 and which front each other. Faces 14 and 15 define a gap between them.

Each ledge 12 and 13 includes a connector passage 16 and 17, respectively.

The hinge pin 5 is located towards the vertically upper extremity of the shank holder 2 and connector element 4. It will be noted that ledges 12 and 13, protrusion 6, and therefore passages 7, 16 and 17 are *spaced vertically below the hinge pin The shank holder 2 is hingable about hinge pin relative to connector element 4 and is hingable into 15 and out of the normal towing position, which is the position shown in Figure i.

S.In the operative towing) position, the protrusion 6 is received as a close fit in the gap 20 between the faces 14 and 15. Also, in this position the passages 7, 16 and 17 are coaxial. Furthermore, the faces 10 and 14 are parallel to, and abut each other.

Likewise the faces 11 and 15 are parallel to, and abut, each other. In addition, openings 8 and 18 are adjacent to, and in register with, each other. Likewise, openings 9 and 19 are adjacent to, and in register with, each other. Consequently when the shank holder 2 is in its operative position, the coupling device 1 can receive a sacrificial pin through the openings 8, 9, 18 and 19, and into the passages 7, 16 and 17.

Hinging of the shank holder 2 out of the operative position causes the protrusion 6 to move out of the gap between the walls 14 and 15. Hence it causes the passage 7 to move laterally relative to the passages 16 and 17. This results in the walls 10 and 11 sliding relative to the walls 14 and 15, respectively, for shearing of the sacrificial pin. This is discussed in more detail below.

The ledge 12 has a face 21 which faces in an opposite direction to the face 14. There is a recess 22 in face 21. The passage 16, at the end opposite the opening 18, has an opening 23 through the face 21 at recess 22.

Similarly, the ledge 13 has a face 24 which faces in an opposite direction to face 15. There is a recess 25 in the face 24. Passage 17, at the end opposite the opening 19, has an opening 26 through the face 24 at recess 15 Each recess 22, 25 is effective for accommodating the head of a sacrificial pin. This is S. also discussed in more detail below.

The shank connector 4 includes a pair of arms S 20 27, 37. Arms 27, 37 extend on opposite sides of the shank holder 2. The arms are for providing lateral support to the shank holder 2, when in use.

The shank holder 2 defines a shank passage 28 for accommodating the shank 3. The passage 28 has inner surfaces 29, 39 each of which defines an upward extending recess 30, The shank connector 4 has two pairs of apertures 31 and 32 for receiving bolts. These are for attaching the connector element 4 to the tool bar of the draft vehicle. Where connector element 4 is attached to a small tool bar, apertures 32 are used. Where the connector element 4 is attached to a large tool bar, apertures 31 can be used.

In use, the shank 3 is accommodated in passage 28. The shank is clamped by a pair of bolts (not shown) which pass through holes 33 in shank holder 2.

Tightening the bolts causes the shank holder 2 to deform.

This squeezes shank 3 in position in passage 28. The position of the shank 3 is established by positionmarking ribs (not shown) which are integral with, and protrude from, the shank. The ribs are accommodated in recesses 30, The shank holder 2 is retained in its operative position by a headed sacrificial pin (not shown). The sacrificial pin extends downwards through passages 16, 7 and 17. The head of the sacrificial pin is accommodated in recess 22. The head prevents the sacrificial pin from S. dropping out through opening 26.

The draft vehicle to which connector element 4 S. is attached moves in the direction shown by arrow 34 in Figure 1. If the lower end of the shank 3 encounters an obstacle preventing movement in its towing direction, 20 this causes a force to be exerted on the shank in the direction shown by arrow 35. This in turn causes shank holder 2 to rotate about hinge pin 5, relative to connector element 4. Further, this causes protrusion 6 to move out of the gap between the faces 14 and 15 of the ledges 12, 13. However, such movement, and hence such rotation, is resisted by the sacrificial pin. However, since the sacrificial pin is fabricated from a material having a low resistance to shear failure, it therefore fails by shear before the shank 3 is damaged.

The arms 27 provide lateral support to the shank holder 2. This is in the case the shank 3 encounters an obstacle which causes a lateral force to be exerted on it.

In Figure 1, the coupling device 1 is shown arranged for connection to the trailing side of the tool bar. It should be noted, however, that the configuration 11 of the coupling device 1 allows it to be connected to the leading side of the tool bar. In this case, the coupling device 1 is inverted relative to the position shown in Figure 2. (The coupling device 1 is not shown in the inverted position). Clearly in the inverted position, the orientation of the shank 3 relative to the shank holder 2 is also required to be inverted. The shank 3 must be inverted so that it still extends downwards even though the coupling device 1 is inverted. In this case the sacrificial pin is inserted through passage 17 by passing it through the opening 26. It is prevented from dropping through opening 23 by virtue of its enlarged head. Its head is accommodated in the recess o 15 The direction of the draft vehicle when the coupling device 1 is used in its inverted orientation is indicated by arrow 37. If the shank 3 indicated by broken chain lines 36 encounters an obstacle preventing its movement in a towing direction, this causes a force to be exerted on the shank 3 in the direction shown by arrow 38. This causes the shank holder 2 to rotate relative to the connector element 4 about hinge axis This in turn causes protrusion 6 to move out of the gap defined by the faces 14 and 15. The movement of the protrusion 6 out of the gap is prevented by the sacrificial pin. Consequently a shear force is exerted on the sacrificial pin. This occurs in a similar manner as when the coupling device 11 is connected to the trailing side of the tool bar, as discussed above.

It will be clear from the above description that the present invention provides a useful device for coupling the shank of an implement to be towed to the tool bar of a towing vehicle, which does not have the disadvantages of the aforementioned prior art devices.

Although the invention has been described with reference to specific examples it will be appreciated by 12 those skilled in the art that it may be embodied in many other forms.

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Claims (9)

1. A coupling device for coupling the shank of an implement to be towed to the tool bar of a towing vehicle, said coupling device comprising a connector plate and a shank holder, said shank holder being connected to said connector plate by a hinged connection, said connector plate including two ledges projecting from a face thereof to accommodate a protrusion on the shank holder, wherein said ledges and said protrusion are joined together by a sacrificial pin, the construction and arrangement being such that when the shank contacts an obstacle hindering its movement in a towing direction, the shank causes the holder to rotate about its hinged connection and the sacrificial pin to shear as the 15 protrusion on the holder is forced away from the ledges on the connecting plate. p S-

2. A coupling device as claimed in claim 1, wherein the ledges project perpendicular to the connector 20 plate and parallel to one another. ee

3. A coupling device as claimed in claim 1 or claim 2, wherein the sacrificial pin extends through aligned passageways in the ledges and the protrusion on the shank holder.

4. A coupling device as claimed in any one of claims 1 to 3, wherein the hinged connection has a hinge axis which is substantially horizontal in use.

A coupling device as claimed in claim 4, wherein the hinged connection is formed at the upper, in use, vertical extremity of the shank holder and connector plate, and the ledges are spaced vertically therefrom toward the lower, in use, end of the connector plate.

6. A coupling device as claimed in claim 3, wherein the aligned passageways in the ledges and the *j N I. ir 14 protrusion adopt an essentially vertical arrangement when the shank holder is in a normal towing situation.

7. A coupling device as claimed in claim 6, wherein the passageways in the ledges each include an enlarged section to accommodate the head of a headed sacrificial pin.

8. A coupling device as claimed in any one of the preceding claims, wherein the connector plate includes a pair of cantilever arms extending on opposite sides of the shank holder which provide lateral support to the shank holder. 15

9. A coupling device as claimed in any one of the preceding claims, wherein the shank holder defines a shank passage for accommodating the shank, the shank S. passage having an inner surface defining a longitudinal recess for position-marking ribs forming part of the 20 shank holder. *aay A coupling device for coupling the shank of an implement to the tool bar of a draft vehicle, substantially as herein described with reference to the accompanying drawings. DATED this 20th day of April 2000 P H RURAL LIMITED By their Patent Attorneys CULLEN CO.