Patent Description:
A tractor is an important agricultural vehicle specifically designed to provide a high tractive effort at slow speeds. A wheel plays a vital role in agricultural vehicles, and helps to carry out various tasks. The wheels in conjunction with axles allow heavy objects to be moved easily facilitating movement or transportation while supporting a load.

The main parts of the wheel are a rim, a disc which are connected by a member lug (Connecting bracket), which is attached to the rim. The rim is an outer edge of a wheel, holding a tire. Disc mates with the hub on the center portion and extended towards rim to meet at lug. A disc is one solid part radiating from the center of a wheel (the hub where the axle connects), connecting the hub with the round traction surface. The term originally referred to portions of a lug which had been split lengthwise into four, six or eight sections. To support the rim structure, a disc can be made by stamping the metal plate.

A conventional uniform thickness disc profile is illustrated in <FIG>. The disc profile includes an axle mounting area <NUM>, an axle mounting radius area <NUM>, a wheel weight mounting area <NUM> and a connection bracket mounting area <NUM>. According to an embodiment, the conventional uniform thickness disc means uniform thickness plate stamped to obtain the profile. The conventional uniform thickness disc profile uses large material input for imparting higher fatigue life. Conventionally, the weight of the wheel is increased to enhance the performance of the wheel. Also, the stress level of the disc under loaded condition is higher at the nave. As a result of high stress at the nave, there is a need for thicker profile on the disc, otherwise it may result in bolt hole failures in uniform thickness wheel profiles. On the other hand the disc radiating above the hub contact region possess less stress concentration, where the uniform thickness adds the weight and does not require an equal thickness of nave. Further, the disc region which connects the lug region through fasteners where the thickness is mandatory for the assembly intact and avoid key hole enlargement.

<CIT> provides a wheel disc and rim to increase the clearance between the wheel and the brake components without increasing the diameter of the wheel. The wheel disc includes a tapered wall thickness of the disc in the intermediate connecting portion. <CIT> is related to the wheel disc that is fixed to the wheel rim through welding or other permanent means.

<CIT> provides a wheel disk having a non-uniform thickness for preventing stress from concentrating at a weld portion between the wheel and the disc. <CIT> is specific to wheel discs that are permanently fixed to the wheel rim through welding.

However, both <CIT> and <CIT> are not related to agricultural wheels wherein the wheel disc is mounted to the wheel rim through fasteners.

Therefore, there is a need for a disc wheel with variable thickness on selected segment for agricultural tractor application to overcome the problem associated with the prior art. Further, there is a need for a disc wheel with variable thickness which uses less material input for imparting high strength. Still, there is a need for a disc wheel with variable thickness to prevent bolt hole failures.

Some of the objects of the present disclosure are described herein below:
A main object of the present invention is to provide a disc wheel with variable thickness for agricultural tractor application.

Another object of the present invention is to provide a disc wheel with variable thickness with a maximum thickness at the centre and gradually reduced thickness up to the end of the wheel weight mounting area achieved using flow form process.

Still another object of the present invention is to provide a disc wheel with variable thickness which uses less material input for imparting high strength.

Yet another object of the present invention is to provide a disc wheel with variable thickness to prevent bolt hole failures.

Another object of the present invention is to provide a thickness gradually decreasing from the axle mounting area up to the end of the wheel weight mounting area in a range of (<NUM> to <NUM>) T.

Another object on the invention is to achieve no spinning on the outer portion of the disc where it connects to lug to avoid keyhole enlargement and avoid stress concentration at the lug weld region.

Another object of the invention is to achieve spinning of square blanks with or without hole and achieving the variable thickness in between the axle mounting area and connection bracket mounting area.

The other objects and advantages of the present invention will be apparent from the following description when read in conjunction with the accompanying drawings which are incorporated for illustration of preferred embodiments of the present invention and are not intended to limit the scope thereof.

In view of the foregoing, the invention provides a disc wheel with variable thickness for agricultural tractor application. According to the invention, a disc wheel with variable thickness includes an axle mounting area, an axle mounting radius area, a wheel weight mounting area and a connection bracket mounting area. Thickness of the axle mounting area is T. The axle mounting radius area is connected to the wheel weight mounting area and the thickness of the connection bracket mounting area is same as that of the thickness of the axle mounting area. The thickness of the disc wheel includes a maximum thickness at the axle mounting area and at the connection bracket mounting area; wherein said thickness from the axle mounting area gradually decreases up to the end of the wheel weight mounting area and matches the thickness at the connection bracket mounting area using flow form process; wherein said thickness of the wheel weight mounting area is less than the thickness of the axle mounting radius area and the thickness of the axle mounting radius area is less than the thickness of the connection bracket mounting area; and wherein said disc wheel with variable thickness uses less material input for imparting high strength.

According to an embodiment, the thickness of the axle mounting radius area is <NUM> % - <NUM>% of the thickness of the axle mounting area. The thickness of the wheel weight mounting area is up to <NUM>% of the thickness of the axle mounting area and the thickness of the connection bracket mounting area is untouched during flow forming process and possesses same thickness as that of the axle mounting area. Therefore, said thickness of the axle mounting radius area is in a range of (<NUM> to <NUM>) T and thickness of the wheel weight mounting area is in the range of (<NUM> to <NUM>) T. The disc wheel with variable thickness prevents bolt hole failures by providing higher strength at the axle mounting area.

According to an embodiment, tensile strength of the disc is typically <NUM> MPa to <NUM> MPa. The tensile strength of the axle mounting radius area is enhanced by flow forming process based on input material strength and degree of reduction in thickness. The increase in strength would be typically <NUM> to 400MPa from input material strength.

According to an embodiment, thickness ratio from the axle mounting area to the end of the axle mounting radius area is T to (<NUM> to <NUM>) T; wherein said thickness ratio from the axle mounting area to the end of the wheel weight mounting area is T to (<NUM> to <NUM>) T. The disc wheel with variable thickness provides good stress distribution and reduces wheel weight. The disc wheel with variable thickness is formed by flow form process and thereby provides non-uniform thickness across the disc profile.

According to an embodiment, the method for forming a disc wheel using a flow forming process comprising the steps of, spinning a square blank with or without hole in a circular mandrel; forming disc using flow forming process in the square blank ; reducing thickness of the disc gradually from the axle mounting area up to the end of the wheel weight mounting area without affecting thickness of an axle mounting area and a connection bracket mounting area; and piercing and clipping edge of the formed disc.

In the figures the use of the same reference numbers in different figures indicates similar or identical items.

The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and detailed in the following description. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein.

As mentioned above, there is a need for a disc wheel with variable thickness for agricultural tractor application. The embodiments herein achieve this by providing a disc wheel with variable thickness with maximum thickness at a centre and gradually reduced thickness towards up to the mounting bracket area using flow form process. Referring now to drawings, and more particularly to <FIG>, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

In accordance with the invention, a novel disc wheel profile with variable thickness <NUM> for agricultural tractor application is illustrated in <FIG>. The disc wheel profile with variable thickness includes an axle mounting area <NUM>, an axle mounting radius area <NUM>, a wheel weight mounting area <NUM> and a connection bracket mounting area <NUM>. The novel disc wheel profile with variable thickness includes a maximum thickness at a centre (hereinafter as axle mounting area <NUM>) and connecting bracket area <NUM>.

According to an embodiment, the axle mounting area <NUM> extends to the wheel axis. The axle mounting radius area <NUM> is connected to the wheel weight mounting area <NUM>. Further, the axle mounting radius area <NUM> has a same thickness as the connection bracket mounting area <NUM>.

According to the invention, the thickness from the axle mounting area 201gradually decreases up to the end of the wheel weight mounting area <NUM> and matches the thickness at the connection bracket mounting area <NUM> using flow form process <NUM>. The thickness of the wheel weight mounting area <NUM> is less than the thickness of the axle mounting radius area <NUM> and the thickness of the axle mounting radius area <NUM> is less than the thickness of the connection bracket mounting area <NUM>. The disc wheel <NUM> with variable thickness uses less material input for imparting high strength. The disc wheel <NUM> with variable thickness prevents bolt hole failures by providing higher strength at the axle mounting area <NUM>. The disc wheel <NUM> with variable thickness provides good stress distribution and reduces wheel weight.

According to the invention, the thickness of the disc wheel <NUM> includes a maximum thickness at the axle mounting area <NUM> and at the connection bracket mounting area <NUM>. According to an embodiment, the thickness of the axle mounting radius area <NUM> is in a range of (<NUM> to <NUM>) T. According to an embodiment, the tensile strength of the axle mounting area <NUM> is 300Mpa to 800Mpa.

According to an embodiment, the thickness of the wheel weight mounting area <NUM> is <NUM>% of the thickness of the axle mounting area <NUM> and the tensile strength may be increased due to flow forming process. Therefore, thickness of the wheel weight mounting area <NUM> is in a range of (<NUM> to <NUM>) T.

In an embodiment, the tensile strength of a region between the axle mounting radius area <NUM> and the wheel weight mounting area <NUM> can be increased 50MPa to 400MPa from raw materials strength.

In accordance with an embodiment, <FIG> illustrates a plan view of a conventional uniform thickness disc profile <NUM> and a novel disc wheel profile with variable thickness. The thickness of the axle mounting area <NUM> is T. The thickness from the axle mounting area 201gradually decreases up to the end of the wheel weight mounting area <NUM> and matches the thickness at the connection bracket mounting area <NUM> using flow form process <NUM>.

According to an embodiment, thickness ratio from the axle mounting area <NUM> to the axle mounting radius area <NUM> is T to (<NUM> to <NUM>) T. The thickness ratio from the axle mounting area <NUM> to the wheel weight mounting area <NUM> is T up to ( <NUM> to <NUM>) T.

The input material for the spinning operation is in square form with less width than the final component. Spinning process achieves the thickness reduction and as well as increases its width and length to the final dimension.

<FIG> illustrates a comparison <NUM> between methods for forming disc wheel using conventional process and flow forming process, according to the invention.

The disc wheel <NUM> with variable thickness is formed by flow form process and thereby provides non-uniform thickness across disc profile. The method for forming a disc wheel in a conventional process <NUM> comprising the steps of, spinning a round blank <NUM>/a obtained from square blank <NUM>, the circular disc <NUM>/a is spinned to achieve the profile in a circular mandrel <NUM>, forming a shape for the wheel disc using disc forming <NUM>, piercing and clipping edge of the disc formed during disc forming <NUM>. Conventionally for spinning the disc, round shaped blanks are taken to spin the material and extend the diameter in outward direction. The square shaped disc such as agricultural wheel may result in huge material waste in getting the final product by this conventional process. The present invention paves the way for innovative process design to achieve the variable thickness disc by almost negligible material waste.

Claim 1:
A disc wheel (<NUM>) with variable thickness for agricultural tractor application comprising:
an axle mounting area (<NUM>) having a thickness T;
an axle mounting radius area (<NUM>) connecting to a wheel weight mounting area (<NUM>);
a connection bracket mounting area (<NUM>) having a thickness T3 same as the thickness T of the axle mounting area (<NUM>);
characterized in that,
said thickness of the disc wheel (<NUM>) includes maximum thicknessT at the axle mounting area (<NUM>) and at the connection bracket mounting area (<NUM>);
wherein said thickness T from the axle mounting area (<NUM>) gradually decreases up to the end of the wheel weight mounting area (<NUM>) and matches the thickness T3 at the connection bracket mounting area (<NUM>);
wherein the thickness T2 of the wheel weight mounting area (<NUM>) is less than the thickness T1 of the axle mounting radius area (<NUM>) and the thickness T1 of the axle mounting radius area (<NUM>) is less than the thickness T of the axle mounting area (<NUM>); and
wherein the connection bracket mounting area (<NUM>) is parallel to the axle mounting area (<NUM>)