DESC:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“OPTIMIZED PERFORMANCE OF TRACTOR DRAFT CONTROL SYSTEM FOR HARD & SOFT SOIL APPLICATIONS”

APPLICANT:

Name Nationality Address
Mahindra & Mahindra Ltd.
Indian Mahindra & Mahindra Ltd.,MRV, Mahindra World City (MWC),Plot No. 41/1, Anjur Post, Chengalpattu, Kanchipuram District – 603204 (TN) INDIA

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

TECHNICAL FIELD
[001] The embodiments described herein relates generally to a draft control system for an agricultural tractor and more particularly to a draft control system which is capable of working in all operating conditions i.e. from soft soil to hard soil.
BACKGROUND
[002] The tractors used for agricultural purposes have many requirements based on several parameters such as soil condition, depth of dig, operating force required and so on. Hard soil requires higher operating draft force, which needs more stronger and reliable parts as compared to light soil which requires lesser operating forces to be sensed by sensing mechanism which needs to be highly sensitive for such smaller loads. Due to these extreme operating conditions it becomes challenging to optimize the system for hard and soft soil conditions. Hence there is a need to design a single draft control system, which will work satisfactorily in all operating conditions i.e. from soft soil to hard soil.
OBJECTS
[003] The principal object of an embodiment of this invention is to provide a draft control system for a vehicle, which could be used in different operating conditions i.e. hard soil and soft soil.
[004] Another object of an embodiment of this invention is to provide a tractor draft control system that regulates the depth of operation of an implement in accordance with draft forces.
[005] Yet another object of an embodiment of this invention is to provide a draft control system, which is of reliable, simplified construction to facilitate its manufacture, its initial assembly, and its adjustment.
[006] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
SUMMARY
[007] A hydraulic draft control system for a vehicle includes, a position control linkage comprising a position control lever for raising and lowering a hitch of the vehicle, a draft control linkage comprising a draft control lever for setting draft of the hitch, a draft spring system for sensing a load exerted by a top link of the hitch, a bell crank for transmitting the load exerted by the top link of the hitch to the draft spring system in a predefined feedback ratio, a response control valve adapted for increasing and decreasing fluid flow inside said control valve. The control valve provides fluid flow proportional to displacement of main spool of control valve and independent of weight of an implement coupled with said hitch.
BRIEF DESCRIPTION OF FIGURES
[008] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[009] Fig. 1 depicts a draft control system of a tractor according to an embodiment of the present invention;
[0010] Fig. 2 depicts a control valve of the draft control system according to an embodiment of the present invention;
[0011] Fig. 3 depicts the control valve of the draft control system when the valve is held in neutral position according to an embodiment of the present invention;
[0012] Fig. 4 depicts the control valve of the draft control system when the valve is held in raised/lifted position according to an embodiment of the present invention;
[0013] Fig. 5 depicts the control valve of the draft control system when the valve is held in lowered position according to an embodiment of the present invention;
[0014] Fig. 6 depicts a response control valve according to an embodiment of the present invention;
[0015] Fig. 7 depicts position control linkages according to an embodiment of the present invention;
[0016] Fig. 8 depicts draft control linkages according to an embodiment of the present invention;
[0017] Fig. 9 depicts draft spring system according to an embodiment of the present invention;
[0018] Fig. 10a and 10b depicts bell crank arrangement in two different positions according to an embodiment of the present invention;
[0019] Fig. 11 depicts control lever quadrant showing position and draft control levers according to an embodiment of the present invention.

DETAILED DESCRIPTION
[0020] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. 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. For example, it should be noted that while some embodiments are explained with respect to a draft control system (100) which is used in a tractor, it should be noted that the draft control system (100) as disclosed in the present invention could also be used for several other purposes by incorporating the subject matter of the invention with little or no modifications. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0021] The embodiments herein relates to a draft control system (100) which could be used in all operating conditions i.e. from hard soil to soft soil as described herein below. The embodiments herein achieve a hydraulic draft control system (100) that regulates the depth of operation of an implement in accordance with draft forces. The embodiments herein further achieve a draft control system (100), which provides reliability, simplified construction thereby facilitating the manufacture, initial assembly and adjustment. Referring now to the drawings, and more particularly to FIGS. 1 through 11, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments. Fig. 1 depicts a draft control system 100 of a tractor according to an embodiment of the present invention. The draft control system (100) includes a control valve (101), internal linkages, draft spring system and a bell crank arrangement.
[0022] Fig. 2 depicts a control valve (101) of the draft control system (100) according to an embodiment of the present invention. The control valve (101) typically includes a main spool (106) connected to a hydraulic system. The hydraulic system includes a relief valve, an unloading valve, a flow control valve, a check valve, a lowering valve, an isolator valve, a lowering speed control valve, a pilot port, a regulator piston (108), a ball regulator valve, a lift cylinder (107) and a shock load relief valve.
[0023] The control valve (101) is the key and major element in the draft control performance of the tractor. The response of hydraulics system for draft signal is decided by control valve (101) flow characteristics. The control valve (101) flow characteristics are fine-tuned suitably to operate in light soil and hard soil applications. Further the control valve (101) regulates the fluid flow to lift cylinder (107) as a function of main spool (106) movement. The control valve (101) is devised to hold three positions namely neutral, raise/lift and lower during its operation.
[0024] Fig. 3 depicts the control valve (101) of the draft control system 100 when the valve is held in neutral position according to an embodiment of the present invention. In neutral position, the main spool (106) is displaced such that the pilot port is closed. The closed position of the pilot port results in pressure build up which moves the regulator piston (108) and unseats the ball-regulator valve allowing pump flow to a reservoir through the port. The lift cylinder (107) is held in this position due to the oil locked in the lift cylinder (107).
[0025] Fig. 4 depicts the control valve (101) of the draft control system 100 when the valve is held in raised/lifted position according to an embodiment of the present invention. When the main spool (106) is moved to lift position inside the control valve (101) the pilot port is opened. The resulting pressure drop allows the regulator piston (108) to move, which seats the ball and directs the oil through lifting port. Then, the oil flows to the lift cylinder (107) through the check valve. As the rockshaft rotates and lift arms rises, the position control cam rotates which moves main spool (106) through position control linkages. The movement of the main spool (106) towards outside closes the pilot port. The resulting pressure build up moves the regulator piston (108) and unseats the ball-regulator valve allowing the pump flow to the reservoir through the port. The lift arms are held in this position due to the oil locked in the lift cylinder (107).
[0026] Fig. 5 depicts the control valve (101) of the draft control system 100 when the valve is held in lowered position according to an embodiment of the present invention. When the main spool (106) is moved to lower position, the oil moves from the lift cylinder (107) to the reservoir through control valve lowering port and lowering tank port. This causes the implement to fall under its own weight. As the pressure is unchanged, the regulator ball is held off its seat and pump flow is circulated in the reservoir.
[0027] In an embodiment the draft control system (100) is said to be proportional. The control valve (101) passes the fluid proportional to the main spool (106) displacement which is independent of load on the lift cylinder (107). This enables implement movement proportional to draft signal at top link. If there is a small draft signal, the main spool (106) will pass a small amount of oil to the lift cylinder (107). This results in small movement of the lift cylinder (107) and implement, irrespective of the implement weight. If there is comparatively more draft signal, control valve will pass comparatively more oil to the lift cylinder (107) and there will be movement of implement. Thus the draft control system (100) is proportional to the draft signal. The fluid flow in the lift cylinder (107) is a function of control valve (101) movement and is called flow characteristics of the valve. This flow characteristic of control valve (101) is optimized for hard and soft soil conditions.
[0028] Fig. 6 depicts a response control valve (103) according to an embodiment of the present invention. In an embodiment the draft control system (100) includes a response control valve (103) which is used to change the flow setting of the control valve (101). The response control valve (103) is operated by means of an adjustable knob (104). The movement of knob (104) towards inside increases the flow to the lift cylinder (107) and hence results in a faster response and outside movement of knob (104) reduces the flow to the lift cylinder (107) resulting in a slower response. The response is selected based on the operation needs.
[0029] In an embodiment the draft control system (100) includes internal linkages coupled with the control valve (101) for position control and draft control of the hitch. Therefore, the internal linkages include a position control linkage and a draft control linkage controlled by a position control lever (PC) and a draft control lever (DC). When operating the position control lever (PC) the draft control lever (DC) is kept in fully forward position and similarly when the draft control lever (DC) is operated the position control lever (PC) is kept in fully forward direction.
[0030] Fig. 11 depicts control lever quadrant (105) showing position control lever (201) and draft control lever (301) according to an embodiment of the present invention. The control lever quadrant (105) having the two control levers namely, Position Control (PC) Lever and Draft Control (DC) lever. The PC lever (201) is located inside towards driver seat while the DC lever (301) is located outside towards fender. These levers are respectively connected to PC and DC internal linkages. The PC lever (201) and DC lever (301) are used to set PC and DC commands for hydraulics system.
[0031] Fig. 7 depicts position control linkages according to an embodiment of the present invention. In an embodiment the position control linkages includes a PC lever (201), a PC connecting link (202), a PC cross shaft (203), a PC cam (204), a roller link (205) and an PC actuating link (206). The main spool (106) of the control valve (101) is in contact with the PC actuating link (206). During lift, the PC lever (201) is moved towards back in the control lever quadrant (105), for lifting of the hitch. As the PC connecting link (202) is connected with the PC lever (201) and PC cam (204), movement of the PC lever (201) results in the rotation of the PC cam (204) mounted on the PC cross shaft (203). The rotation of the PC cam (204) moves the roller link (205) downward. The downward movement of the roller link (205) moves the PC actuating link (206) which under the action of a return spring pushes the main spool (106) inside the control valve (101). This inside movement of main spool (106) results in diversion of pump flow to lift cylinder (107) resulting in piston and rockshaft movement which finally leads in lifting of hitch and implement attached to hitch. The lifting of hitch rotates the PC cam (204) which in turn moves the roller link (205) towards the control valve (101). Further main spool (106) moves outward in the control valve (101) which positions the control valve (101) in neutral position and facilitates in holding the hitch in set position.
[0032] When PC lever (201) is moved forward, the PC cross shaft (203) and PC cam (204) rotates clockwise and the roller link (205) moves on the PC cam (204). This results in movement of the PC actuating link (206) which allows the main spool (106) inside the control valve (101) to move outwards under the action of the spring main valve. This lowers the hitch to set position. At set position the main spool (106) will come to neutral by a feedback from the PC cam (204) and roller link (205).
[0033] Fig. 8 depicts draft control linkages according to an embodiment of the present invention. In an embodiment the draft control linkages includes a DC lever (301), a DC connecting link (302), a DC actuating link (305), a spring feedback link (306), a DC plunger (307), and a draft link (308). For setting the draft, the draft control lever (301), is moved forward or backward as per requirement. The movement of the DC lever (301) defines a gap between a DC actuating link (305) and main spool (106) of control valve (101). This gap determines the setting of the draft for the particular operation and thus the depth of operation of the implement is set. The DC lever (301) is used for setting the draft and the DC plunger (307), spring feedback link (306) and DC actuating link (305) is used for transmitting feedback signal from draft sensing spring to control valve 101. The internal linkages and position of bell crank decide the ratios (X/Y) setting command and feedback. These ratios (X/Y) are optimized suitably for light and hard soils.
[0034] Fig. 9 depicts draft spring system according to an embodiment of the present invention. In an embodiment the draft spring system includes a spring housing (410), a plurality of spring seats (401, 404), DC spring (402), bell crank (403), a locknut (405), a plurality of seams (408 and 409), and a spindle (406) as shown in fig. 10. The draft spring system facilitates in balancing the top link force given by the used implement attached to tractor by means of three point linkages. The draft spring system is sensitive enough to sense the light loads experienced in sandy soil applications like leveller and at the same time having enough capability of taking heavy loads of ploughing operation. In an embodiment the draft control system (100) could be optimized by changing spring stiffness, assembly clearances and layout in such a way that there are minimum frictional losses of draft control signal sensed by DC spring (402). The spring is kept horizontal for minimum frictional loss.
[0035] In draft control mode, the DC lever (301) is set in a particular position on the control quadrant (105). As the top link is attached to bell crank (403), under the top link force, the DC spring (402) will deflect. This displacement of DC spring (402) due to top link force is passed to DC plunger (307) which is kept always in contact with bell crank (403) by return spring. The movement of DC plunger (307) is transferred to the main spool (106) of the control valve (101) with certain amplification through draft link (308) and DC actuating link (305). This result in lifting of the implement in operation till the set force is reached. If the implement is lifted more than required height, the top link force is reduced and the bell crank (403) will go back. The backward movement of bell crank (403) will lower the implement till the set draft is achieved.
[0036] Fig. 10a and 10b depicts bell crank arrangement in two different positions according to an embodiment of the present invention. The bell crank (403) transmits top link force (draft signal) to DC spring (402) in a predefined ratio. This is achieved by providing two holes at particular location with respect to pivot point of the bell crank (403) and spring attachment point. Two holes are provided to change the draft sensitivity. The hole away from pivot point gives higher sensitivity and the hole closer to pivot point gives lesser sensitivity, due to change in feedback ratio. In one embodiment the pivot point of bell crank (403) is located below the DC spring (402) and in another embodiment the pivot point of bell crank (403) is located above the DC spring (402) providing two different feedback ratios for higher and lower sensitivity.
[0037] 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, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
,CLAIMS:We claim
1. A hydraulic draft control system for a vehicle, said hydraulic draft control system comprising:
a position control linkage comprising a position control lever adapted for raising and lowering a hitch of said vehicle and a PC actuating link provided in communication with a main spool of a control valve;
a draft control linkage comprising a draft control lever adapted for setting draft of said hitch and a DC actuating link provided in communication with said main spool of said control valve;
a draft spring system adapted for sensing a load exerted by a top link of said hitch, wherein said draft spring system is provided in communication with said draft control linkage;
a bell crank adapted for transmitting said load exerted by said top link of said hitch to said draft spring system in a predefined feedback ratio wherein said bell crank has a plurality of opening adapted for connecting said bell crank with said top link and each of said opening with respect to a pivot point of said bell crank and said draft spring system, provides different degrees of draft sensitivity; and
a response control valve adapted for increasing and decreasing fluid flow inside said control valve,
wherein
said control valve provides fluid flow proportional to displacement of said main spool of said control valve and independent of weight of an implement coupled with said hitch.
2. The hydraulic draft control system as claimed in claim 1, wherein said system provides draft proportional to said load exerted by said top link.
3. The hydraulic draft control system as claimed in claim 1, wherein said system further comprises a control lever quadrant adapted for holding said position control lever and said draft control lever.
4. The hydraulic draft control system as claimed in claim 1, wherein said position control linkage includes a PC connecting link, a PC cross shaft, a PC cam, and a roller link, wherein said PC cam is mounted on said PC cross shaft, and said roller link is provided in communication with said PC cam and said PC actuating link, and said PC connecting link is provided in communication with said position control lever and said PC cam.
5. The draft control linkage as claimed in claim 1 further comprises a DC connecting link, a spring feedback link, a draft link and a DC plunger wherein said DC plunger is provided in communication with said draft spring system and said draft link, and said spring feedback link is provided in communication with said draft link and said DC actuating link, and said DC connecting link is provided in communication with said draft control lever and said PC cam.
6. The hydraulic draft control system as claimed in claim 1, wherein said pivot point of said bell crank and said draft spring system is positioned above said draft spring system.
7. The hydraulic draft control system as claimed in claim 1, wherein said pivot point of said bell crank and said draft spring system is positioned below said draft spring system.
8. The hydraulic draft control system as claimed in claim 1, wherein said vehicle is a tractor.

Date: 28th August 2014 Signature:
Kalyan Chakravarthy