Claims:We claim:
1. A feedback mechanism (100) for controlling fluid flow in a hydro-static transmission of a vehicle, said feedback mechanism (100) comprising:
a trunnion shaft lever (108);
a movable member (106) adapted to be loaded into said trunnion shaft lever (108) through a first resilient member (105), wherein said movable member (106) defines a plurality of locking member engaging portions (106A, 106B & 106C);
a main lever (102) adapted to be connected to said movable member (106) through a main lever connecting member (104);
a locking member (112) adapted to be selectively engaged with one of said locking member engaging portions (106A, 106B & 106C) defined on said movable member (106); and
a release lever (105) adapted to be connected to said locking member (112) through a release lever connecting member (111).

2. The feedback mechanism (100) as claimed in claim 1, wherein said feedback mechanism (100) includes,
an end cover (107) mounted onto a top end of said trunnion shaft lever (108),
wherein
one end of said first resilient member (105) is engaged with said end cover (107) and another end of said first resilient member (105) is engaged with a collar (106CR) defined on said movable member (106);
said first resilient member (105) is at least a spring;
one end of said main lever connecting member (104) is connected to said main lever (102) and another end of said main lever connecting member (104) is connected to said movable member (106); and
said main lever connecting member (104) is at least a cable.

3. The feedback mechanism (100) as claimed in claim 2, wherein said feedback mechanism (100) includes,
a pivot lever mounting bracket (118) adapted to be secured to said trunnion shaft lever (108); and
a pivot lever (114) adapted to be pivotably mounted onto said pivot lever mounting bracket (118), wherein said pivot lever (114) is connected to said locking member (112),
wherein
said locking member (112) adapted to be loaded against said trunnion shaft lever (108) through a second resilient member (116),
one end of said release lever connecting member (111) is connected to said release lever (105) and another end of said release lever connecting member (111) is connected to said pivot lever (114);
said release lever connecting member (111) is at least a cable;
one end of said second resilient member (116) is engaged with a collar (112C) defined on said locking member (112) and another end of said second resilient member (116) is coupled with said pivot lever (114); and
said second resilient member (116) is at least a spring;

4. The feedback mechanism (100) as claimed in claim 3, wherein said feedback mechanism (100) includes,
a stopper (109) adapted to limit said ingress of said movable member (106) within said trunnion shaft lever (108) beyond a predefined position;
a cable holding bracket (120) adapted to hold said release lever connecting member (111); and
a fastener (117) adapted to secure said pivot lever mounting bracket (118) to said trunnion shaft lever (108),
wherein
said stopper (109) defines a movable member receiving portion (cavity or opening) adapted to allow a linear movement of said movable member (106) during a movement of said main lever (102)

5. The feedback mechanism (100) as claimed in claim 1, wherein said locking member (112) is adapted to disengage from one of said plurality of locking member engaging portions (106A, 106B, 106C) on pressing said release lever (110);
said movable member (106) is adapted to be moved with respect to said trunnion shaft lever (108) on movement of said main lever (102); and
said locking member (112) is adapted to engage with respective locking member engaging portions (106A or 106B or 106C) on depressing said release lever (110) thereby changing length of ingress (loading) of said movable member (106) with respect to said trunnion shaft lever (108),
wherein
said trunnion shaft lever (108) abuts against a trunnion shaft (122); and
the change in length of ingress (loading) of movable member (106) with respect to trunnion shaft lever (108) facilitates a variation in the rate of fluid flow in said hydro-static transmission.

6. The feedback mechanism (100) as claimed in claim 5, wherein said feedback mechanism (100) includes,
a forward direction control pedal adapted to be movably coupled to the trunnion shaft lever (108) through a plurality of first linkages and said stopper (109); and
a reverse direction control pedal (not shown) adapted to be movably coupled to the trunnion shaft lever (108) through a plurality of second linkages and said stopper (109).

7. The feedback mechanism as claimed in claim 6, wherein the engagement of said locking member (112) with one of the locking member engaging portions (106A-106C) of said movable member (106) defines the degree of contact of said trunnion shaft lever (108) with respect to the trunnion shaft (122) which in turn corresponds at which degree the trunnion shaft lever (108) can rotate with respect to the trunnion shaft (122);
the change in length of ingress (loading) of said movable member (106) within said trunnion shaft lever (108) defines a change in pressure applied by said trunnion shaft lever (108) on the trunnion shaft (122) which in-turn leads to the variation in magnitude of rotation of said trunnion shaft (122); and
the degree (magnitude) of rotation of said trunnion shaft (122) changes a rate of hydraulic fluid flow in the hydro-static transmission which in-turn varies a speed of the vehicle one operation of one of said forward direction control pedal or said reverse direction control pedal.

8. The feedback mechanism (100) as claimed in claim 7, wherein the degree (magnitude) of rotation of said trunnion shaft (122) controls the quantity of hydraulic fluid delivered from a hydraulic pump.

9. A method (500) for controlling fluid flow in a hydro-static transmission of a vehicle, said method (500) comprising:
disengaging (502), by a release lever (110), a locking member (112) from respective locking member engaging portion (106A) of a movable member (106) through a release lever connecting member (111) and a pivot lever (114) by pressing the release lever (110);
moving (504), by a main lever (102), the movable member (106) through a main lever connecting member (104); and
depressing (506), the release lever (110) for engaging the locking member (112) with another locking member engaging portion (106B or 106C) of the movable member (106) to change a length of ingress of the movable member (106) with respect to a trunnion shaft lever (108) which in turn facilitates a variation in the rate of fluid flow in the hydro-static transmission.

10. The method (500) as claimed in claim 9, wherein said method (500) includes,
varying (508), by the trunnion shaft lever (108), a degree of rotation of trunnion shaft (122) thereby controlling fluid flow in the hydro-static transmission on operation forward or reverse direction control pedals,
wherein
the engagement of said locking member (112) with one of the locking member engaging portions (106A-106C) of said movable member (106) defines the degree of contact of said trunnion shaft lever (108) with respect to the trunnion shaft (122) which in turn corresponds at which degree the trunnion shaft lever (108) can rotate with respect to the trunnion shaft (122);
the change in length of ingress (loading) of said movable member (106) within said trunnion shaft lever (108) defines a change in pressure applied by said trunnion shaft lever (108) on the trunnion shaft (122) which in-turn leads to the variation in magnitude of rotation of said trunnion shaft (122); and
the degree (magnitude) of rotation of said trunnion shaft (122) changes rate of hydraulic fluid flow in the hydro-static transmission which in-turn varies a speed of the vehicle on operation of one of said forward direction control pedal or said reverse direction control pedal.
, Description:TECHNICAL FIELD
[001] The embodiments herein generally relates to a hydro-static transmission in a vehicle and more particularly, to a feedback mechanism for controlling fluid flow in the hydro-static transmission of the vehicle such as a tractor.
BACKGROUND
[002] In the case of a hydro-static transmission (HST) of an off-road vehicle, an internal combustion (IC) engine is used to drive a hydraulic pump which in turn provides pressurized fluid with the help of a motor to drive the wheels. For vehicles with HST, there is a lever whose movement in one direction, say forward, will cause the hydraulic pump to allow fluid flow in a direction that causes the vehicle to move forward. However, since the quantity of fluid and rate of flow is fixed, there is a need to give variations in speed similar to the speed variations as provided by a mechanical transmission.

[003] A conventional control system for a utility vehicle transmission provides for operator selection of vehicle "aggressiveness” or rates of acceleration in response to operator command. The aggressiveness of vehicle's performance can be controlled by modulating control signals to proportional control valves, which determine the transmission acceleration, according to two or more electrical ramp-up or ramp-down profiles, in response to an operator's acceleration command or deceleration command. The transmission control system includes a controller, directional switches and electro-hydraulic valves which are used to control hydraulic pressure in the servo control system of the hydrostatic transmission. The operator is provided with a two-position set switch. With the set switch in the less aggressive position, in response to the operator's command, the software in the controller provides a relatively slow current ramp to energize the control valves. With the switch in the more aggressive position, the current ramps and resultant pressure ramps are faster, thus causing more aggressive transmission operation for the hydrostatic transmission.

OBJECTS
[004] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
[005] An object of the present invention is to provide a feedback mechanism for controlling fluid flow in a hydro-static transmission of a vehicle such as a tractor.
[006] Another object of embodiments herein is to provide a method for controlling fluid flow in the hydro-static transmission of the vehicle.
[007] Another object of embodiments herein is to provide a mechanical type feedback mechanism for controlling fluid flow in the hydro-static transmission.
[008] Another object of the invention is to provide a feedback to the user in terms of variation in operating speed of vehicle while using hydro-static transmission.
[009] 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.

BRIEF DESCRIPTION OF DRAWINGS
[0010] The foregoing and other features of embodiments of the present invention will become more apparent from the following detailed description of embodiments when read in conjunction with the accompanying drawings. In the drawings, like reference numerals refer to like elements.
[0011] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it is not intended to limit the scope of the invention to these embodiments.
[0012] Figure 1 illustrates a feedback mechanism for controlling fluid flow in a hydro-static transmission system of a vehicle, where the feedback mechanism is in a first position (aggressive speed position), according to embodiments as disclosed herein;
[0013] Figure 2 illustrates the feedback mechanism in a second position (slow speed position), according to embodiments as disclosed herein;
[0014] Figure 3 illustrates the feedback mechanism in a third position (normal speed position), according to embodiments as disclosed herein;
[0015] Figure 4 illustrates the feedback mechanism in the first position (aggressive speed position), according to embodiments as disclosed herein; and
[0016] Figure 5 illustrates a flowchart indicating steps of a method for controlling fluid flow in the hydro-static transmission system of the vehicle, according to embodiments as disclosed herein.

DETAILED DESCRIPTION
[0017] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which shown by way of illustration specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable a person skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, and other changes may be made within the scope of the embodiments. Also, the words “comprising,” “having,” “containing,” and “including,” and other similar forms are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. The following detailed description is, therefore, not be taken as limiting the scope of the invention, but instead the invention is to be defined by the appended claims The terms “first resilient member” and “second resilient member” used herein in the specification is to be understood with respect to a reference object.

[0018] Figure 1 illustrates a feedback mechanism (100) for controlling fluid flow in a hydro-static transmission of a vehicle, where the feedback mechanism (100) is in a first position (aggressive speed position), according to embodiments as disclosed herein. In an embodiment, the feedback mechanism (100) comprises a main lever (102), a main lever connecting member (104), a first resilient member (105), a movable member (106), an end cover (107), a trunnion shaft lever (108), a stopper (109), a release lever (110), a release lever connecting member (111), a locking member (112), a pivot lever (114), a second resilient member (116), a fastener (117), a pivot lever mounting bracket (118), a cable holding bracket (120) and a trunnion shaft (122). For the purpose of this description and ease of understanding, the feedback mechanism (100) is explained herein with below reference to controlling fluid flow in the hydro-static transmission of an off-road vehicle such as a tractor. However, it is also within the scope of this invention to use/practice the feedback mechanism (100) for controlling fluid flow in the hydro-static transmission of any other vehicles without otherwise deterring the intended function of the feedback mechanism (100) as can be deduced from the description and corresponding drawings.
[0019] The main lever (102) is connected to the movable member (106) through the main lever connecting member (104). One end of the main lever connecting member (104) is connected to the main lever (102) and another end of the main lever connecting member (104) is connected to the movable member (106). For the purpose of this description and ease of understanding, the main lever connecting member (104) is considered to be a cable. However, it is also within the scope of invention to use rods or any other linkages for connecting the main lever (102) with the movable member (106) without otherwise deterring the intended function of the main lever connecting member (104) as can be deduced from the description and corresponding drawings.
[0020] One end of the first resilient member (105) is engaged with a collar ((106CR), (as shown in fig. 2) defined on the movable member (106), and another end of the first resilient member (105) is engaged with the end cover (107). For the purpose of this description and ease of understanding, the first resilient member (105) is considered to be a spring. The movable member (106) is adapted to be loaded into the trunnion shaft lever (108) through the first resilient member (105). The movable member (106) defines a plurality of locking member engaging portions ((106A, 106B and 106C), (as shown in fig. 1 to fig. 4)).
[0021] The end cover (107) is mounted at a top end of the trunnion shaft lever (108). The end cover (107) is adapted to support the first resilient member (105) and the movable member (106). The end cover (107) is adapted to restrict the releasing of the movable member (106) from the trunnion shaft lever (108) during movement of the movable member (106) in response to movement of the main lever (102). The stopper (109) defines a movable member receiving portion (cavity or opening) adapted to allow a linear movement of the movable member (106) during the movement of the main lever (102). Further, the stopper (109) is adapted to limit the ingress of the movable member (106) within the trunnion shaft lever (108) beyond a predefined position.
[0022] The release lever (110) is adapted to be connected to the locking member (112) through the release lever connecting member (111) and the pivot lever (114). The release lever (110) is located on the main lever (102). One end of the release lever connecting member (111) is connected to the release lever (110) and another end of the release lever connecting member (111) is connected to the pivot lever (114). For the purpose of this description and ease of understanding, the release lever connecting member (111) is considered to be a cable. However, it is also within the scope of invention to use rods or any other linkages for connecting the release lever (110) with the locking member (112) without otherwise deterring the intended function of the release lever connecting member (111) as can be deduced from the description and corresponding drawings.
[0023] The locking member (112) is adapted to be loaded against the trunnion shaft lever (108) through the second resilient member (116). The locking member (112) is adapted to be selectively engaged with one of the locking member engaging portions (106A, 106B & 106C) defined on the movable member (106).
[0024] The pivot lever (114) is located on one side of the trunnion shaft lever (108). The pivot lever (114) is adapted to be pivotably mounted on the pivot lever mounting bracket (118). The pivot lever (114) is adapted to support the locking member (112) against the trunnion shaft lever (108). The pivot lever (114) is adapted to move the locking member (112) to engage or dis-engage the locking member (112) with respect to the movable member (106) on depressing or pressing the release lever (110) respectively. One end of the second resilient member (116) is engaged with a collar ((112C), as shown in fig. 1)) defined on the locking member (112) and another end of second resilient member (116) is engaged with the pivot lever (114) through a connecting pin (121), (as shown in fig. 1)). The second resilient member (116) is at least a spring. The pivot lever mounting bracket (118) is secured to the trunnion shaft lever (108) through the fastener (117), where the fastener (117) is considered to be a bolt. The cable holding bracket (120) is adapted to hold the release lever connecting member (111).
[0025] Further, the feedback mechanism (100) includes a forward direction control pedal (not shown) and a reverse direction control pedal (not shown). The forward direction control pedal is adapted to be movably coupled to the trunnion shaft lever (108) through a plurality of first linkages (not shown) and the stopper (109). The reverse direction control pedal is adapted to be movably coupled to the trunnion shaft lever (108) through a plurality of second linkages (not shown) and the stopper (109).

[0026] For understanding the disclosed feedback mechanism 100 is used in the hydro-static transmission, the system will be described below considering a user (operator) using the feedback mechanism (100) to achieve various speeds in the hydro-static transmission with reference to FIG. 1 to FIG. 4. The feedback mechanism (100) is in a first position ((aggressive speed position), (as shown in fig. 1)), where the locking member (112) is engaged with the locking member engaging portion (106C) of the movable member (106), and the vehicle is configured to be operated at higher speeds. The feedback mechanism (100) is in a second position ((slow speed position), (as shown in fig. 2)), where the locking member (112) is engaged with the locking member engaging portion (106A) of the movable member (106), and the vehicle is configured to be operated at slower speeds. The feedback mechanism (100) is in a third position ((normal speed position), (as shown in fig. 3)), where the locking member (112) is engaged with the locking member engaging portion (106B) of the movable member (106), and the vehicle is configured to be operated at normal speeds.
[0027] Figure 3 illustrates the feedback mechanism (100) in the third position (normal speed position), according to embodiments as disclosed herein. For example, if the locking member (112) is engaged with the locking member engaging portion (106C) of the movable member (106) as illustrated in FIG. 1, then in order to engage the locking member (112) with the another locking member engaging portion (106B) as illustrated in FIG. 3, the user needs to disengage the locking member (112) from the locking member engaging portion (106A) of the movable member (106) by operating (pressing) the release lever (110), and then operating the main lever (102) for moving the movable member (106). Depressing the release lever (110) for engaging the locking member (112) with one of the locking member engaging portions (106B or 106C) to change the length of ingress (loading) of the movable member (106) with respect to the trunnion shaft lever (108) facilitates a variation in the rate of fluid flow in said hydro-static transmission. This is because if the locking member (112) is engaged with the locking member engaging portion (106B) of the movable member (106), will not allow further loading of the movable member (106) into the trunnion shaft lever (108). Now, the feedback mechanism (100) is in the third position (normal speed position), where the vehicle is configured to be operated at normal speeds. The engagement of the locking member (112) with locking member engaging portion (106B) defines the degree of contact of the trunnion shaft lever (108) with respect to the trunnion shaft (122) which in turn corresponds at which degree the trunnion shaft lever (108) can rotate with respect to the trunnion shaft (122). Based upon the length of ingress (loading) of the movable member (106) within the trunnion shaft lever (108), the pressure applied by the trunnion shaft lever (108) on the trunnion shaft (122) changes and this in-turn leads to the variation in magnitude of rotation of the trunnion shaft (122) thereby facilitating a variation in the rate of fluid flow in said hydro-static transmission. Based upon the degree of rotation of the trunnion shaft (122) in this case D1, the hydraulic fluid flowing through the hydro-static transmission is varied which in-turn varies speed of the vehicle on operation of one of the forward direction control pedal or the reverse direction control pedal.
[0028] Figure 2 illustrates the feedback mechanism (100) is in a second position (slow speed position), according to embodiments as disclosed herein. Now, referring to FIG. 2, to achieve a speed, the magnitude of which is different from the speed as achieved through the detailed description of FIG. 3, the user needs to press the release lever (105) to disengage the locking member (112) from the locking member engaging portion (106B) of the movable member (106). As the locking member (112) disengages from the locking member engaging portion 106B, the movable member (106) is free to move within the trunnion shaft lever (108), the user then moves the main lever (102) to a position such that the locking member engaging portion 106A of the movable member (106) is aligned to receive the locking member (112). Upon, depressing the release lever (110), the locking member (112) engages with the locking member engaging portion 106A, the degree to which the trunnion shaft (122) can rotate is now (D2). Now, the feedback mechanism (100) is in the second position (slow speed position), where the vehicle is configured to be operated at slow speeds. Since magnitude of D2 is different from D1, the hydraulic fluid flowing through the hydro-static transmission system is controlled in dependence of the magnitude D2 and this in-turn gives variation in speed of the vehicle on operation of one of the forward direction control pedal or the reverse direction control pedal.
[0029] Now, referring to FIG. 4, the user presses the release lever (110) to disengage the locking member (112) from one of the locking member engaging portion ((106A), (as shown in fig. 2) or (106B), (as shown in fig. 3)) of the movable member (106). As the locking member (112)) disengages from one of the locking member engaging portion (106A or 106B), the movable member (106) is free to move within the trunnion shaft lever (108), the user then moves the main lever (102) to a position such that the locking member engaging portion 106C of the movable member (106) is aligned to receive the locking member (112). Upon, depressing the release lever (110), the locking member (112) engages with the locking member engaging portion 106C, the degree to which the trunnion shaft (122) can rotate is now (D3). Now, the feedback mechanism (100) is in the first position (aggressive speed position), where the vehicle is configured to be operated at slow speeds. Since magnitude of D3 is different from D2 and D1, the hydraulic fluid flowing through the hydro-static transmission is controlled in dependence of the magnitude D3 and this in-turn gives variation in speed of the vehicle on operation of one of the forward direction control pedal or the reverse direction control pedal.
[0030] Figure 5 illustrates a flowchart indicating steps of a method (500) for controlling flow of fluid in a hydro-static transmission of a vehicle. The method (500) comprises disengaging (502), by a release lever (110), a locking member (112) from respective locking member engaging portion (106A) of a movable member (106) through a release lever connecting member (111) and a pivot lever (114) by pressing the release lever (110). The method (500) includes moving (504), by a main lever (102), the movable member (106) through a main lever connecting member (104). Depressing (506), the release lever (110) for engaging the locking member (112) with another locking member engaging portion (106B or 106C) of the movable member (106) to change length of ingress (loading) of movable member (106) with respect to trunnion shaft lever (108) therein to change a degree of contact of the trunnion shaft lever (108) with respect to the trunnion shaft (122) which in turn corresponds at which degree the trunnion shaft lever (108) can rotate with respect to the trunnion shaft (122) thereby facilitating a change in fluid flow in hydro-static transmission, and varying (508), by the trunnion shaft lever (108), a degree of rotation of trunnion shaft (122) for controlling fluid flow in the hydro-static transmission on operating forward or reverse direction control pedals.
Advantages:
1. The feedback mechanism (100) provides various speed modes in hydro-static transmission of the vehicle.
2. The feedback mechanism (100) provides various speed modes for the hydro-static transmission in both forward and reverse driving condition of the vehicle.
[0031] 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.
[0032] 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. The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which these embodiments may be used and to further enable the skilled person in the relevant art to practice the invention.
[0033] Although, the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification by making innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.
[0034] 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.
[0035] Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to imply 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.
[0036] 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.
[0037] These relative terms are for convenience of description and do not require that the corresponding apparatus or device be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “main lever” and “release lever”, refer to a relationship, wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.