Claims:We claim:

1. A lower-link of hollow box-section for three-point linkage system in tractors, the lower link comprising:

- a middle box-section, and
- a pair of profiled solid eye sections,

wherein each end of the middle box-section is permanently joined to one of the profiled solid eyes by means of welding.

2. Hollow section lower-link as claimed in claim 1, wherein the hollow box-section has a substantially rectangular section having wider flat sides and narrower sides with rounded or non-rounded corners respectively.

3. Hollow section lower-link as claimed in claim 1, wherein the hollow box-section has a rectangular section having wider flat sides and narrower thin sides respectively.

4. Hollow section lower-link as claimed in claim 2 or 3, wherein the hollow box-section includes one or more through holes drilled along the width of the wider flat side at each ends thereof and a pair of spacers inserted therein along the length thereof and to be subsequently plug welded adjacent one of the ends thereof.

5. Hollow section lower-link as claimed in claim 1, wherein the profiled solid eyes comprises a through opening at one end for hitching an agricultural implement and at the other end thereof includes a pair of holes drilled on the flat wider side thereof corresponding to the pitch of the through holes drilled on the hollow box-section.

6. Hollow section lower-link as claimed in claim 3, wherein a reinforcement ring with through holes on both wider sides thereof, congruent with the holes on the spacer inserted in the hollow box-section adjacent one end thereof, before subsequent plug welding of the spacer on the hollow box-section.

7. Hollow section lower-link as claimed in claim 1, wherein the solid eye comprises a through opening for hitching an agricultural implement at one end and a wedge shaped thickened section to be inserted into the hollow box-section and having a pair of holes drilled on the flat wider side thereof corresponding to the pitch of the through holes drilled on the hollow box-section.

8. Hollow section lower-link as claimed in claim 1, wherein the solid eyes are inserted inside the two ends of the hollow box-section and plug welded at the through holes and arc welded at the periphery of the joint of the eyes with the hollow box-section for configuring the hollow section lower link.

9. Hollow section lower-link as claimed in claim 1, wherein the hollow box-section is made of sheet metal of 3 to 5 mm, preferably 4 mm thickness by bending and welding and solid eyes are die-forged, both hollow section and eyes are made of steel, preferably a material such as EN19B or SAE 5150 or any other similar material.

10. Method for manufacturing a hollow section lower-link as claimed in claims 1 to 8, wherein the method comprises the following method steps:

- Making a hollow box-section from a piece of sheet metal by cutting, bending and welding or rolling ERW tube in box section and drilling the holes for plug welding at predetermined locations,

- Forging the solid eyes by closed-die forging,

- Drilling holes for plug welding,

- Machining the spacers for insertion into the hollow box-section,

- Inserting the spacers and locating them at predetermined locations for plug welding,

- Inserting a solid eye at each end of the hollow box-section,

- Performing plug welding at the holes on the solid eyes and on the spacers, and

- Performing arc welding all around the periphery of the joint of the hollow box-section and the solid eyes in order to obtain the finished hollow box-section lower link.

11. Method for manufacturing a hollow section lower-link as claimed in claims 10, wherein a reinforcing ring is also inserted over the spacer adjacent the solid eye and plug welded thereon after obtaining the hollow box-section lower link.

Dated: this 22nd day of October, 2015. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to the three-point linkage/hitch system for tractors. In particular, it relates to the lower-link of the three-point linkage system. More particularly, the present invention relates to reducing the weight and cost of the lower-link of the three-point linkage system in tractors.

BACKGROUND OF THE INVENTION

In agricultural tractors, one of the most important units is the three-point linkage or hitch system. It is used to attach various implements to the tractor, so that the orientation of the implement can be fixed with respect to the tractor and to the arm position of the linkage. Since tractor carries partial or full weight of the implement, its three-point linkage system transfers the weight and resistance of the implement to the drive wheels of the tractor. This facilitates in making more traction available to the tractor than without any such three-point linkage system, however for the same power and weight and therefore, with the same fuel consumption.

The three-point linkage system is operated by the hydraulic system of the tractor and includes the points for attachment, lifting arms, and stabilizers. In fact, three-point linkage is made of three movable arms, i.e. two lower arms generally controlled by the tractor’s own hydraulic system for lifting, lowering, and tilting of these arms and the upper center arm or the top link. Each arm has an arrangement for connecting any desired implement to the three-point linkage. For attaching an implement, a plurality of holes is provided on each link, through which, the posts of the implement are secured by inserting a respective pin at the ends of these posts. The lifting arms of the three-point linkage are powered by the tractor's own hydraulic system, which is controlled by the tractor operator by means of different available settings. Normally, a draft control mechanism is also provided in the three-point linkage, so that the draft of the implement, i.e. the amount of force taken for pulling the implement can be sensed on the lower arms and they can be slightly raised or lowered automatically with increased or reduced draft by the tractor’s hydraulic system.

DISADVANTAGES WITH THE PRIOR ART

Therefore, the weight of the three-point linkage system is a very significant criterion for an effective field operation of the tractor. The presently available

The major disadvantage with the presently available three-point linkages is that the links are heavy, thereby the

Therefore, there is a long felt need for eliminating the disadvantages associated with the conventional

DESCRIPTION OF THE PRESENT INVENTION

To explain the typical construction of a 3-point linkage or hitch system for a tractor, the schematic arrangements described according to the American Society of Agricultural and Biological Engineers are shown in Figures 1 to 4.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a three-point linkage system for tractors.

Another object of the present invention is to provide a low-weight three-point linkage system for tractors.

Still another object of the present invention is to eliminate costly welding for a three-point linkage system for tractors.

Yet another object of the present invention is to reduce the manufacturing cost of the three-point linkage system for tractors.

These and other objects and advantages of the present invention will become more apparent from the following description when read with the accompanying figures of drawing, which are, however, not intended to limit the scope of the present invention in any way.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a lower-link of hollow box-section for three-point linkage system in tractors, the lower link comprising:
- a middle box-section, and
- a pair of profiled solid eye sections,

wherein each end of the middle box-section is permanently joined to one of the profiled solid eyes by means of welding.

Typically, the hollow box-section has a substantially rectangular section having wider flat sides and narrower sides with rounded or not rounded corners respectively.

Typically, the hollow box-section has a rectangular section having wider flat sides and narrower thin sides respectively.

Typically, the hollow box-section includes one or more through holes drilled along the width of the wider flat side at each ends thereof and a pair of spacers inserted therein along the length thereof and to be subsequently plug welded adjacent one of the ends thereof.

Typically, the profiled solid eyes comprises a through opening at one end for hitching an agricultural implement and at the other end thereof includes a pair of holes drilled on the flat wider side thereof corresponding to the pitch of the through holes drilled on the hollow box-section.

Typically, a reinforcement ring with through holes on both wider sides thereof, congruent with the holes on the spacer inserted in the hollow box-section adjacent one end thereof, before subsequent plug welding of the spacer on the hollow box-section.

Typically, the solid eye comprises a through opening for hitching an agricultural implement at one end and a wedge shaped thickened section to be inserted into the hollow box-section and having a pair of holes drilled on the flat wider side thereof corresponding to the pitch of the through holes drilled on the hollow box-section.

Typically, the solid eyes are inserted inside the two ends of the hollow box-section and plug welded at the through holes and arc welded at the periphery of the joint of the eyes with the hollow box-section for configuring the hollow section lower link.

Typically, the hollow box-section is made of sheet metal of 3 to 5 mm, preferably 4 mm thickness by bending and welding or using ERW tube rolled in box section and solid eyes are die-forged, both hollow section and eyes are made of steel, preferably a material such as EN19B or SAE 5150 or any other similar material.

In accordance with the present invention, there is also provided a method for manufacturing a hollow section lower-link, the method comprises the steps of:

- Making a hollow box-section from a piece of sheet metal by cutting, bending and welding or rolling ERW tube in box section and drilling the holes for plug welding at predetermined locations,

- Forging the solid eyes by closed-die forging,

- Drilling holes for plug welding,

- Machining the spacers for insertion into the hollow box-section,

- Inserting the spacers and locating them at predetermined locations for plug welding,

- Inserting a solid eye at each end of the hollow box-section,

- Performing plug welding at the holes on the solid eyes and on the spacers, and

- Performing arc welding all around the periphery of the joint of the hollow box-section and the solid eyes in order to obtain the finished hollow box-section lower link.

Typically, a reinforcing ring is also inserted over the spacer adjacent the solid eye and plug welded thereon after obtaining the hollow box-section lower link.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings, which include:

Figure 1 shows a typical 3-point linkage/hitch system for attaching different agricultural implements to a tractor.

Figure 2 shows the typical dimensions in 3-point linkage system.

Figure 3a shows the typical horizontal convergence distances in a 3-point linkage system on a tractor.

Figure 3b shows the typical vertical convergence distances in a 3-point linkage system on a tractor.

Figure 4 shows an enlarged view of the 3-point linkage system shown in Figure 3b.

Figure 5a shows the conventional substantially rectangular lower link for a tractor.

Figure 5b shows an enlarged view of the rectangular cross-section of the lower link of Figure 5a.

Figure 5c shows a slightly enlarged view of one of the rounded ends of the lower link of Figure 5a.

Figure 6a shows a first embodiment of the lower link for a tractor configured in accordance with the invention.

Figure 6b shows an enlarged view of the rectangular cross-section of the first embodiment of the lower link shown in Figure 6a.

Figure 6c shows a slightly enlarged view of one of the rounded ends of the first embodiment of the lower link shown in Figure 6a.

Figure 7a shows the second embodiment of the lower link for a tractor configured in accordance with the invention.

Figure 7b shows the box cross-section of the lower link of the second embodiment shown in Figure 7a.

Figure 7c shows the solid end part of the lower link of the second embodiment shown in Figure 7a.

Figure 7d shows the details of the welding of the lower link of the second embodiment shown in Figure 7a.

Figure 8a shows the axial loading pattern of the lower link in accordance with the present invention shown in Figures 7a or 8a.

Figure 8b shows the lateral loading pattern of the lower link in accordance with the present invention shown in Figures 7a or 8a.

Figure 8c shows vertical loading pattern of the lower link in accordance with the present invention shown in Figures 7a or 8a.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, different embodiments of the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1 shows different parts of the 3-point linkage or hitch system used in a tractor. The system includes an upper link 1, a lower link 2, an upper hitch point 3, a pair of lower hitch points 4, an upper link point 5, a pair of lower link points 6, an upper hitch attachment 7, a pair of lower hitch attachment 8, an upper link attachment 9, one pair each of linch pins 10, linch rods 11 and masts 12. Here, the mast height 13, lower hitch point span 14 and linch pin hole distance 15 are also indicated.

Figure 2 shows the typical dimensions in 3-point linkage system. They are: the lower hitch point height 16, levelling adjustment 17, movement range 18, transport height 19 and lower hitch point clearance 20.

Figure 3a and 3b show the typical horizontal and vertical convergence distances in a 3-point linkage system for a tractor. Accordingly, upper hitch point 3, lower hitch points 4, upper link point 5, lower link points 6 are also shown. The horizontal convergence distance 21 and vertical convergence distance 22 are also indicated here. The figure also shows the vertical virtual hitch point HPv and horizontal virtual hitch point HPh.

Figure 4 shows an enlarged view of the 3-point linkage system shown in Figure 3b. The upper link 1 with the upper link point 5 and the distance L of the lower link points 6 of the lower links 2 from the power take-off (PTO) 23 are also are shown here.

Figure 5a shows the conventional lower link for a tractor configured as a solid body. It consists of a substantially rectangular section 10, rounded ends 12 provided with a respective through hole 14 at each end thereof. The profiled thicker ends 16 serve as the transition region from rectangular section 10 to the rounded ends 12. The rectangular section 10 is also provided with two holes 18 disposed spaced apart and adjacent one of the ends 12. Of which, one hole is for fixing the lift rod and the other hole is for fixing the check-chain. A typical conventional lower link weighs about 7.5 kg to 8 kgs.

Figure 5b shows an enlarged view of the cross-section 20 of the rectangular section 10 of Figure 5a, which is taken adjacent one of the holes 18.

Figure 5c shows a slightly enlarged view of one of the rounded ends 12 of the lower link of Figure 5a, which clearly illustrates the transition of the profile between the rounded end 12 and the thicker rectangular section 16.

Figure 6a shows a first embodiment of the lower link for a tractor in accordance with the invention. It is preferably made from an ERW pipe to configure the tubular middle portion of the lower link by flattening. This middle portion is subsequently made into a composite component by secured joining of the tubular middle portion to the two rounded ends 112 (eyes configured with a respective through hole 114) by means of a pair of plug welds 116 at each end thereof on both sides and by arc welding at the joints 124 between the rounded ends 112 and the flattened middle portion of the lower link. This flattened tubular middle portion has a slightly rounded thin side 110 and a flat wider side 122. Two spacers 118 are also provided adjacent one of the plug-welded ends 116 of the lower link. These spacers 118 with a hole are placed inside the lower link box-section to avoid collapsing of flattened box-section. The lower link tubular middle portion and the rounded ends (with eye) are preferably made of steel, more preferably of EN19B or SAE 5150 steel. A typical configuration of one such composite lower link manufactured according to the present invention weighs just about 6 to 6.5 kg, which is substantially less than the conventional lower link shown in Figures 5a. Since two (2) lower-links are used per three-point linkage system in a tractor, the total weight reduction for the three-point linkage system alone is at least about 3 kgs per tractor. This weight reduction also helps in bringing down the overall cost of the three-point linkage system and also reduces the tendency of lifting of the tractors front end due to heavy weight of the three-point linkage system.

Figure 6b shows an enlarged view of the rectangular cross-section 120 of the of the composite lower link shown in Figure 6a, which is bound by two flat wider sides 122 and two rounded narrower sides 110. One of the spacers 118 is also shown.

Figure 6c shows a slightly enlarged view of one of the rounded ends of the composite lower link shown in Figure 6a. This enlarged view illustrates the welded joints between the rounded end 112 and the tubular flattened portion.

Figure 7a shows the second embodiment of the lower link of a three-point linkage/hitch system configured in accordance with the invention. Here, the flat and rounded tubular middle portion is replaced by a rectangular box section 210 provided with the reinforcement 228 having a hole 230 provided adjacent one of the ends 212 of the lower link, also configured with a respective through hole 214. The hole 230 is meant for checking the chain mounting. This second embodiment is configured to take up heavier loads than the first embodiment, since the rounded ends 212 are made with substantially thicker wedge-shaped ends 226 joined to the middle box section 210. The plug welds 216 and arc welds 224 are similar to the first embodiment in Figure 6a. However, the spacer 218 is provided here substantially at the center of the middle portion 210. The typical configuration of this composite lower link manufactured according to the second embodiment of the present invention weighs just about 8.5 to 9 kg, which is substantially less than the conventional lower link of this type having a weight of about 13 kg. This means a weight saving of about 8 to 9 kg per pair of lower links in every tractor.

Figure 7b shows the box cross-section 220 of the lower link of the second embodiment of Figure 7a. The reinforcement 228 provided with a hole 230 is fixed on the box-section 210 of the lower link. The reinforcement 228 reduces the stress in this area. A spacer 218 is also shown here, which safeguards the middle box section of the lower link from collapsing as in the first embodiment.

Figure 7c shows one of the solid end parts 212 of the lower link of the second embodiment of Figure 7a. The rounded end 212 having a through hole 214 is made with a substantially thicker wedge-shaped end 226 leading to a rectangular box section 232, which can be snugly fitted inside the middle rectangular box-section 210 and subsequently joined thereto by means of a respective pair of plug welds 216. The hole 214 is provided for attaching the lower link to the implement to be connected to the tractor.

Figure 7d shows the detailed view of the fitting and welding of the rounded end 212 of Figure 7c to the box-section 210 of the lower link of Figure 7a. The plug welds 216 and arc welds 224 are used for securely joining the rounded ends 212 to the middle rectangular box section 210 of the lower link according to the present invention for handling the implements connected to the tractor by means of the three-point linkage system.

Figure 8a shows the axial loading pattern of the lower link 100 or 200 in accordance with the present invention as shown in Figures 7a or 8a. The applied axial load AL in x direction causes the restraint translation through LHS hole 214 (in figure here) is in all x, y and z directions. However, the restraint translation through RHS hole 214 (in figure here) is only in y and z directions. The lower link tubular middle portion and the rounded ends (with eye) are preferably made of steel, more preferably of EN19B or SAE 5150 steel.

Figure 8b shows the lateral loading pattern of the lower link 100 or 200 in accordance with the present invention as shown in Figures 7a or 8a. The applied lateral or transverse load TL in y direction causes the restraint translation through LHS hole 214 (in figure here) is in all x, y and z directions. However, the restraint translation through RHS hole 214 (in figure here) is only in z direction. Simultaneously, a restraint translation in x, y and z directions along with a rotation R about the x axis is noticed in the local coordinate system (LCS).

Figure 8c shows vertical loading pattern of the lower link 100 or 200 in accordance with the present invention as shown in Figures 7a or 8a. The applied vertical load VL in z direction causes the restraint translation through LHS hole 214 (in figure here) is in all x, y and z directions. In addition, the restraint translation through the centrally disposed spacer 218 is also in all x, y and z directions, however accompanied by a rotation about x and z directions

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The lower-link of hollow box-section for three-point linkage system in tractors in accordance with the present invention has the following major advantages:
• Reduced weight
• Lower manufacturing cost
• Tools and dies costs are lower
• Reduces tractor front-end lifting
• Costly fusion welding is eliminated.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.

The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.

Although, only the preferred embodiments have been described herein, the skilled person in the art would readily recognize to apply these embodiments with any modification possible within the spirit and scope of the present invention as described in this specification.

Therefore, innumerable changes, variations, modifications, alterations may be made and/or integrations in terms of materials and method used may be devised to configure, manufacture and assemble various constituents, components, subassemblies and assemblies according to their size, shapes, orientations and interrelationships.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.