DESC:FIELD OF INVENTION

The present invention relates to a draft sensing device for various soil applications of a tractor. In particular, the present invention relates to a hydraulic draft sensing device for tractors. More particularly, the present invention relates to a hydraulic draft sensing spring assembly which can be configured for different soil applications, e.g. hard or soft soil applications.

BACKGROUND OF THE INVENTION

The most important use of tractors is to perform agricultural activities, such as tilling, ploughing etc. by attaching different implements by means of a three-point linkage or hitch system to the tractor. The implements are to be hitched properly for an efficient and safe tractor operation. The hitch system facilitates in fixing the orientation of the implement with respect to the tractor and the arm position of the linkage thereof. Usually, tractor carries a partial or full weight of the attached implement and the hitch system transfers the weight and resistance of the implement to the drive wheels of the tractor to make more traction available to the tractor than a tractor without a hitch system of the same power and weight, but with the same fuel consumption. The hitch system is operated by the hydraulic system of the tractor and includes the points for attachment, lifting arms and stabilizers. The three-point linkage is a combination of three links, one is the upper link and the other two are the lower links. These links are articulated to the tractor and the implements at their ends for connecting the implement to the tractor. The bell crank of the tractor hitch system is a class 1 lever. One side of the bell crank is connected to the top link and the other side is connected to the draft sensing spring.

The draft of the implement, i.e. the amount of force taken for pulling the implement, can be controlled by using a draft control mechanism provided in the three-point linkage. Depending on the increased or reduced draft sensed on the top link, the draft control system automatically slightly raises or lowers the arms by means of the tractor’s hydraulic system.
In an automatic draft control system, the working depth of any implement can be controlled continuously without the need for a depth wheel on the implement. Here, the power lift mechanism is controlled using a draft sensing device that consists of control valve, draft sensing spring and the connecting linkages. The draft sensing spring acts as resistance, whereas the effort acts from the top link. The soil resistance force which acts on the implement, creates a tensile force on the top link. This tensile force creates a compressive force on the draft sensing spring. There is an arrangement of linkages in between the fulcrum and the top link attachment, which senses the displacement due to top link force and spring compression. These linkages finally give signal to the control valve to lift or lower the 3-point linkages. The top link force due to the implement draft and soil reaction cannot be controlled, but the draft sensing spring design can control it. The spring directly converts the sensed force into the displacement of the bell crank. So, the stiffness of the spring plays a vital role in draft sensing operation. If the stiffness is more, the force on the top link must be designed large enough to give the required movement to the sensing linkages to lift the implement and vice-versa.

PRIOR ART

Patent US 4059159 discloses a tractor having a power lift mechanism controllable automatically in known manner by implement draft load sensing apparatus comprising two leaf springs which are spaced apart in a lateral direction relative to the tractor, the springs being connected at their front ends to the tractor and being adapted to flex in the lateral direction but being stiff longitudinally of the tractor and vertically; two hitch links each connected to the rear end of one of the springs; and equipment for transmitting to the power lift mechanism a control signal derived from any variation in the distance between the flexible portions of the springs. It describes a tractor draft control device, where a compound draft control spring is used which provides greater deflection per unit increase of load in the lower range of draft and lesser deflection in the upper range thus facilitating accurate draft control throughout the entire range of draft of which the tractor is capable.

Patent US 3156303 discloses a tractor having a power liftable implement hitch and power means for lifting the hitch; a housing, a draft sensing plunger mounted for movement in a wall of the housing for controlling operation of the power means, means for impressing a force on the plunger generally proportional to draft of an implement connected to the hitch and tending to displace the plunger, and a compound spring formed of a low-rate spring and a high-rate spring coaxial with the plunger, the springs being arranged in end to end abutting relation and extending between the plunger and housing with the high-rate spring extending between the low-rate spring and the housing, the high-rate spring being formed of a series of Belleville washers closely fitting about the plunger, and a radial step formed on the plunger of larger diameter than the portion fitting within the high-rate springs and engaged with the end of the high-rate spring upon removal of the plunger beyond its initial range of movement. It describes a tractor draft control device, where a compound draft control spring is used which provides greater deflection per unit increase of load in the lower range of draft and lesser deflection in the upper range thus facilitating accurate draft control throughout the entire range of draft of which the tractor is capable.

DISADVANTAGES WITH THE PRIOR ART

A dead band (neutral zone or dead zone) is an interval of a signal domain or band where no action occurs (the system is 'dead' - i.e. the output is zero). The dead band of force in the draft sensing operation is the difference between the force required to lift the implement and the force required to lower the implement. A lower dead band means that the sensitivity is more, and a higher dead band means that the sensitivity is less. The tractor application with respect to the soil working can be divided into two major categories, soft soil application and hard soil application. For soft soil applications, the recommended dead band of force is less for optimum levelling, whereas for hard soil applications, the recommended dead band of force is more to avoid implement hunting.

Therefore, it is not possible for a single draft sensing spring to achieve the requirements of both the applications efficiently. So, the modern draft sensing mechanisms consist of a pair of springs (with different stiffness), which are spaced apart in lateral direction relative to the tractor.

However, due to the series arrangement of the draft sensing springs, there are problems faced on a low stiffness spring getting completely compressed during the hard soil applications. Therefore, there is an existing need for addressing the abovementioned issue.

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 draft sensing device for a tractor for use in any type of soil applications.

Another object of the present invention is to provide a draft sensing device for a tractor, which is easy to be operated.

Still another object of the present invention is to provide a draft sensing device for a tractor, which is cost-effective to manufacture.

Yet another object of the present invention is to provide a draft sensing device for a tractor, which provides better control in draft sensing operation.

A further object of the present invention is to provide a draft sensing device for a tractor, which provides a lower dead band force to improve sensitivity during the draft sensing operation.

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.

DESCRIPTION OF THE PRESENT INVENTION

The present invention addresses this issue by describing a novel draft sensing spring assembly, which consists of a high stiffness spring, a low stiffness spring and a separation pin.

From the bell crank side, first the higher stiffness spring is placed and followed by placing the lower stiffness spring (see Figure 1). For soft soil applications, the separation pin is placed after the low stiffness spring to make a compound spring. Therefore, the compound spring’s stiffness is substantially lower than the low stiffness spring (see Figure 2).

For hard soil applications, the separation pin is placed before the low stiffness spring (see Figure 1). Therefore, the low stiffness spring is isolated, and the high stiffness spring starts acting. This compound spring arrangement gives a higher dead band of force for the same tractor during its hard soil applications.

This invention relates to hydraulic draft sensing in an agricultural tractor, in which draft sensing is used for controlling the draft load of the implement. The height of the lower linkages often is controlled in response to the draft on the implement in order to maintain a more or less uniform depth selected by the operator. The implement is raised or lowered automatically, as required, for maintaining the preselected draft of the implement.

When using an implement on hard soils, the draft is relatively high and while using it on soft soils, the draft is much lower. When the implement is in operation, the reaction force of soil is transferred to the implement, resulting in compressive forces acting on the top link and tensile forces acting on the lower link.

This invention is unique compared to abovementioned prior art techniques in following ways:

• A separation pin is used according to the present invention to offer greater control on the draft sensing during hard soil applications. Whereas in the conventional design, the soft spring was getting completely compressed during very hard soil applications.

• By using this separation pin, the soft spring is isolated during hard soil applications, therefore it provides a greater control on the draft sensing operation.

• Further, a high stiffness spring is placed before the lower stiffness spring, which is opposed to the conventional design of lower stiffness spring placed before the higher stiffness spring.

• Therefore, this arrangement provides an easy isolation of the lower stiffness spring by using a separation pin.

• During the simulation of draft sensing springs under different load conditions, the complete compression of soft (low-stiffness) springs was observed at high load in the conventional designs.

• Therefore, this solution is developed to avoid such complete compression of the soft springs occurring the existing arrangements during field application by using the existing systems.

In the draft sensing spring assembly configured according to the present invention, the observed dead band is lower (see Figure 4) and is suitable for soft soil application, by placing the separation pin in between the high and low stiffness springs (see Figure 2).

The hitch regulation is defined as:

% hitch regulation = (FR-FL/FR) x 100
wherein,
FR – Force required to raise the hitch

FL – Force required to lower the hitch.

This hitch regulation is also an indicator of the performance of draft sensing spring. The simulation results (Figure 5) shows that the % hitch regulation for the compound spring arrangement with separation pin configured according to the present invention is at par with that of the soft spring arrangement for soft soil application. In the hard soil application, only the high stiffness spring is active due to the separation pin and this arrangement is as good as the single high stiffness spring configuration recommended for hard soil.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a compound draft sensing spring assembly for different soil applications by a tractor; said assembly comprising:

• a seat for draft sensing spring;

• a spindle top link provided with a plurality of holes (125) at a predetermined pitch from said seat and said spindle top link is fixed thereto;

• at least one high-stiffness spring placed on the outer end of said spindle top link; and

• at least one low-stiffness spring placed on the inner end of said spindle top link fixed on said draft sensing spring seat;

wherein a lockable separation pin is removably disposed at different holes on said spindle top link for selectively operating said draft sensing spring assembly according to the type of soil to be worked on.

Typically, the assembly comprises a high-stiffness spring and a low-stiffness spring and one hole each provided on said draft sensing spring seat before said and after said low-stiffness spring.

Typically, the separation pin is inserted in a hole disposed between said high-stiffness spring and low-stiffness spring to isolate said low-stiffness spring for providing a high dead band for operating the tractor during hard-soil applications.
Typically, the separation pin is inserted in a hole adjacent to the seat for draft sensing spring to use the compound spring formed by said high-stiffness spring and low-stiffness spring for providing a low dead band for operating the tractor during soft-soil applications.

Typically, the outer diameter of said high-stiffness spring is greater than the outer diameter of said low-stiffness spring.

In an embodiment of the present invention, the compound draft sensing spring assembly comprises:

• a seat for draft sensing spring;

• a spindle top link provided with one hole each provided on said draft sensing spring seat before said and after said low-stiffness spring;

• a high-stiffness spring placed on the outer end of said spindle top link for hard-soil applications; and

• a low-stiffness spring placed on the inner end of said spindle top link) fixed on said draft sensing spring seat for soft-soil applications;

wherein said separation pin having a threaded end is inserted in a hole provided between said high-stiffness spring on said spindle top link and locked by a removable nut for isolating said low-stiffness spring to achieve a high dead band for operating the tractor during hard-soil applications.

Typically, the separation pin is inserted in a hole provided before said low-stiffness spring for facilitating the compound spring formed with said high-stiffness spring and said low-stiffness spring to achieve a low dead band for operating the tractor during soft-soil applications.

Typically, the outer diameter of said high-stiffness spring is greater than the outer diameter of said low-stiffness spring.

Typically, the diameter f the wire forming said high-stiffness spring is greater than the diameter of the wire forming said low-stiffness spring.

Typically, the separation pin is a bolt partially threaded for tightening a bolt thereon after insertion of said bolt in one of said holes provided on said draft sensing spring seat.

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 cross-sectional view of the conventional draft sensing spring assembly.

Figure 2 shows a side view of the draft sensing spring assembly configured in accordance with the present invention being used for hard soil applications.

Figure 3 shows a side view draft sensing spring assembly configured in accordance with the present invention being used for soft soil applications.

Figure 4 shows a graphical representation of a comparison of dead bands for low, high and compound stiffness springs respectively for soft soil applications.

Figure 5 shows a graphical representation of simulation results for hitch regulation for low, high and compound stiffness springs respectively for soft soil applications.

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 a cross-sectional view of the conventional draft sensing spring assembly. Here, the higher stiffness spring is placed and thereafter the lower stiffness spring is placed for hard soil applications.

Figure 2 shows a side view of the draft sensing spring assembly 100 configured in accordance with the present invention set-up by positioning the separation pin for hard soil applications. The low stiffness spring gets isolated, and only the high stiffness spring is acting. The draft sensing spring assembly 100 includes a seat spring 110, a spindle top link 120, a high-stiffness spring 130, a low-stiffness spring 140 and a separation pin 150 disposed between these two springs 130 and 140. Accordingly, a high-stiffness spring 130 is placed before the low-stiffness spring 140 and the separation pin 150 is placed (inserted in a hole in the 120 and locked by tightening a nut 156 thereon) before the low stiffness spring 140 to isolate the low-stiffness spring 140. Thus, the high-stiffness spring 130 gets active for providing a high dead band for tractor during hard-soil applications.

Figure 3 shows a side view of the draft sensing spring assembly 100 configured in accordance with the present invention, which is set-up by different positioning of the separation pin 150 for soft soil applications. Here, the separation pin is placed after the low stiffness spring to make a compound spring for soft soil applications. This compound spring arrangement gives a higher dead band of force for the same tractor during its soft soil applications. Therefore, the compound spring’s stiffness is substantially lower than the low stiffness spring. The diameter D of the high-stiffness spring 140 being greater than that of the low-stiffness spring 130. Here, the separation pin 150 is placed after the low stiffness spring 130 to make it a compound spring 160.

Figure 4 shows a graphical representation of improvement in the dead band force achieved through the use of the compound spring 160 configured in accordance with the present invention. It is evident that the amount of dead band force using a single low or high stiffness spring is substantially higher than the compound or double springs used according to the present invention. Since for soft soil application, it is desirable to have a low dead band with respect to the top link force. Here, the results show a comparatively low dead band than the single low or high stiffness spring configurations.

Figure 5 shows a graphical representation of the results of simulation for hitch regulation for low, high and compound stiffness springs respectively, during the soft soil applications. Here, the compound spring configuration shows a substantially lower value of hitch regulation in the curve for the - hitch regulation (-%) v/s force required to raise the hitch (kg), which is more uniformly distributed than the conventional arrangements, in terms of the force required to raise the implement during a soft soil application. It is recommended to have low hitch regulation with respect to top link force for efficient soft soil application

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The draft sensing spring assembly configured in accordance with the present invention has the following advantages:

• Separation pin offers greater control on draft sensing during hard soil application.

• Separation pin isolates the soft spring during hard soil applications.

• Placing the high-stiffness spring before the low-stiffness spring provides an easy isolation of low-stiffness spring by using the separation pin.

• Lower dead band force due to use of compound spring.

• Offers higher sensitivity necessary during soft soil applications.

• Offers an advanced technological feature for the applicant’s tractors.

• A single tractor can be used for any kind of soil application.

• Offers the applicant a market lead by distinguishing this unique feature to achieve new more technology savvy customers.

In the previously detailed description, different features have been summarized for improving the conclusiveness of the representation in one or more examples. However, it should be understood that the above description is merely illustrative, but not limiting under any circumstances. It helps in covering all alternatives, modifications and equivalents of the different features and exemplary embodiments.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept. Many other examples are directly and immediately clear to the skilled person because of his/her professional knowledge in view of the above description.

These 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. Therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

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. The description provided herein is purely by way of example and illustration.

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.
In the claims and the description, the terms “containing” and “having” are used as linguistically neutral terminologies for the corresponding terms “comprising”.

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.

Furthermore, the use of the term “one” shall not exclude the plurality of such features and components described.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

Also, any reference herein to the terms ‘left’ or ‘right, ‘up’ or ‘down, or ‘top’ or ‘bottom’ are used as a matter of mere convenience, and are determined by standing at the rear of the machine facing in its normal direction of travel.

The various features and advantageous details are explained with reference to the non-limiting embodiment/s 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.

Furthermore, the various components shown or described herein for any specific application of this invention can be widely known or used in the art by persons skilled in the art and each will likewise not therefore be discussed in significant detail. When referring to the figures, like parts are numbered the same in all of the figures. ,CLAIMS:We claim:

1. A compound draft sensing spring assembly (100) for different soil applications by a tractor, said assembly comprising:

• a seat (110) for draft sensing spring;

• a spindle top link (120) provided with a plurality of holes (125) at a predetermined pitch from said seat (110) and said spindle top link (120) is fixed thereto;

• at least one high-stiffness spring (130) placed on the outer end of said spindle top link (120); and

• at least one low-stiffness spring (140) placed on the inner end of said spindle top link (120) fixed on said draft sensing spring seat (110);

wherein a lockable separation pin (150) is removably disposed at different holes (125) on said spindle top link (120) for selectively operating said draft sensing spring assembly according to the type of soil to be worked on.

2. Compound draft sensing spring assembly (100) as claimed in claim 1, wherein the assembly comprises a high-stiffness spring (130) and a low-stiffness spring (140) and one hole (125) each provided on said draft sensing spring seat (110) before said and after said low-stiffness spring (140).

3. Compound draft sensing spring assembly (100) as claimed in claim 2, wherein said separation pin (150) is inserted in a hole (125) disposed between said high-stiffness spring (130) and low-stiffness spring (140) to isolate said low-stiffness spring (140) for providing a high dead band for operating the tractor during hard-soil applications.

4. Compound draft sensing spring assembly (100) as claimed in claim 2, wherein said separation pin (150) is inserted in a hole (125) adjacent to the seat (110) for draft sensing spring to use the compound spring formed by said high-stiffness spring (130) and low-stiffness spring (140) for providing a low dead band for operating the tractor during soft-soil applications.
5. Compound draft sensing spring assembly (100) as claimed in anyone of the claims 2 to 4, wherein the outer diameter (D) of said high-stiffness spring (130) is greater than the outer diameter (d) of said low-stiffness spring (140).

6. Compound draft sensing spring assembly (100) as claimed in claim 1, wherein said assembly comprises:

• a seat (110) for draft sensing spring;

• a spindle top link (120) provided with one hole (125) each provided on said draft sensing spring seat (110) before said and after said low-stiffness spring (140);

• a high-stiffness spring (130) placed on the outer end of said spindle top link (120) for hard-soil applications; and

• a low-stiffness spring (140) placed on the inner end of said spindle top link (120) fixed on said draft sensing spring seat (110) for soft-soil applications;

wherein said separation pin (150) having a threaded end is inserted in a hole (125) provided between said high-stiffness spring (130) on said spindle top link (120) and locked by a removable nut for isolating said low-stiffness spring (140) to achieve a high dead band for operating the tractor during hard-soil applications.

7. Compound draft sensing spring assembly (100) as claimed in claim 6, wherein said separation pin (150) is inserted in a hole (125) provided before said low-stiffness spring (140) for facilitating the compound spring formed with said high-stiffness spring (130) and said low-stiffness spring (140) to achieve a low dead band for operating the tractor during soft-soil applications.

8. Compound draft sensing spring assembly (100) as claimed in anyone of the claims 1 to 7, wherein the outer diameter (D) of said high-stiffness spring (130) is greater than the outer diameter (d) of said low-stiffness spring (140).

9. Compound draft sensing spring assembly (100) as claimed in anyone of the claims 1 to 7, wherein the diameter (D1) of the wire forming said high-stiffness spring (130) is greater than the diameter (d1) of the wire forming said low-stiffness spring (140).

10. Compound draft sensing spring assembly (100) as claimed in anyone of the claims 1 to 9, wherein said separation pin (150) is a bolt (150) partially threaded for tightening a bolt (155) thereon after insertion of said bolt (150) in one of said holes (125) provided on said draft sensing spring seat (110).

Dated: this 17th day of January 2017. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT