DESC:CROSS-REFERENCE TO RELATED APPLICATIONS
[001] This application is based on and derives the benefit of Indian Provisional Application 201741011883, the contents of which are incorporated herein by reference.
TECHNICAL FIELD
[002] The embodiments herein generally relate to hydro-static transmission unit in vehicles and more particularly, to a control linkage mechanism for a hydro-static transmission unit of a vehicle.
BACKGROUND
[003] Generally, a hydro-static transmission unit of a vehicle is type of power transmission unit that uses a hydraulic drive propulsion system in place of a standard clutch and geared transmission. The hydro-static transmission unit uses hydraulic fluid forced through a pump to drive the vehicles such as tractors or other similar vehicles. This fluid drive system is controlled by a foot pedal or a hand lever.
[004] Certain vehicles, of which industrial lift trucks and loaders are typical examples, are often equipped with a hydrostatic transmission which provides for infinite variation of the drive ratio between the engine and drive wheels or the like in both forward and reverse drive directions. The drive ratio and the drive direction are controllable by selectively moving a control member away from a central or neutral position. Motion in one direction progressively increases drive ratio in the forward drive mode while motion of the control member in the opposite direction from the neutral position progressively increases drive ratio in the reverse drive mode.
[005] Interconnections between the operator's control member and the transmission and the engine are still further complicated as it is desirable that the operator be able to further increase engine speed after the transmission drive ratio control element has reached its maximum movement in either the forward or reverse direction. This may be desirable, for example, when the vehicle is travelling relatively fast at the maximum available drive ratio and either a further speed increase is desired or the vehicle is subjected to increased loading such as may occur from starting up an inclined slope. It is then necessary to further open the engine throttle, governor rack or the like in order to maintain speed.
[006] Thus, if the operator is to control both the hydrostatic transmission and engine speed with a single control member, the linkage which interconnects these components must be capable of shifting the transmission control element in either direction from a neutral position in accordance with the corresponding movement of the operator's control member and must concurrently shift the engine speed control a proportionate amount but always in the same direction regardless of the direction of movement of the control member. Further, the linkage must enable continued movement of the engine speed control in a single direction after the transmission control has reached the limit of travel in either direction.
[007] Because of these complicated requirements, the linkages heretofore used for interconnecting a single operator's control member with both a hydrostatic transmission and an engine have been undesirably complex and costly.
[008] Therefore, there exists a need for control linkage mechanism for a hydro-static transmission unit of a vehicle, which obviates the aforementioned drawbacks.

OBJECTS
[009] The principal object of an embodiment of this invention is to provide a control linkage mechanism for a hydro-static transmission unit of a vehicle.
[0010] Another object of an embodiment of this invention is to provide a simple, compact, reliable and economical control mechanism enabling optimized control of vehicle speed, drive ratio and drive direction by movement of a single foot control member.
[0011] Yet another object of an embodiment of this invention is to provide a control linkage mechanism having a locking mechanism for a hydro-static transmission unit of a vehicle.
[0012] 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 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.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The embodiments of the invention are 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:
[0014] FIG. 1 depicts a perspective view of a control linkage mechanism for a hydro-static transmission unit of a vehicle, according to a first embodiment of the invention as disclosed herein;
[0015] FIG. 2 depicts a perspective view of a locking mechanism of the control linkage mechanism, according to a first embodiment of the invention as disclosed herein;
[0016] FIG. 3 depicts an another perspective view of a portion of the locking mechanism of the control linkage mechanism, according to a first embodiment of the invention as disclosed herein;
[0017] FIG. 4 depicts a perspective view of a cam roller mechanism of the control linkage mechanism, according to a first embodiment of the invention as disclosed herein;
[0018] FIG. 5 depicts a perspective view of the control linkage mechanism assembled to a housing of the hydro-static transmission unit, according to a first embodiment of the invention as disclosed herein;
[0019] FIG. 6 depicts a perspective view of a locking mechanism of a control linkage mechanism for a hydro-static transmission unit of a vehicle, according to a second embodiment of the invention as disclosed herein; and
[0020] FIG. 7 depicts a perspective view of the control linkage mechanism assembled to a housing of a hydro-static transmission unit, according to a second embodiment of the invention as disclosed herein.

DETAILED DESCRIPTION
[0021] 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. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0022] The embodiments herein achieve a control linkage mechanism for a hydro-static transmission unit of a vehicle. Further, the embodiments herein achieve a simple, compact, reliable and economical control mechanism enabling optimized control of vehicle speed, drive ratio and drive direction by movement of a single foot control member. Referring now to the drawings, and more particularly to FIGS. 1 through 7, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0023] FIG. 1 depicts a perspective view of a control linkage mechanism for a hydro-static transmission unit of a vehicle, according to a first embodiment of the invention as disclosed herein. In first embodiment, the control linkage mechanism 100 for a hydro-static transmission unit of a vehicle includes a foot control member 102, a hand control lever 104, an interconnecting linkage means, a cam roller mechanism, a cam connecting link member 120, a first connecting link member 106, at least two step pads 108a and 108b, a second connecting link member 110, a third connecting link member 111, a plurality of teeth 112, a first pivot member 114, a roller pivot link 116, and a connecting member 118, at least one spring 124
[0024] The control linkage mechanism 100 for the hydro-static transmission unit of the vehicle includes the foot control member 102. The foot control member 102 described herein the description may be a straddle pedal. The foot control member 102 is mounted on the vehicle at a predetermined position. The foot control member 102 is pivotably movable about at a first axis A. The foot control member 102 is adapted to move between a forward position and a backward position from a neutral position. The foot control member 102 includes a first end 102a and a second end 102b. The first end 102a includes a plurality of teeth 112. The plurality of teeth 112 may be defined either in the foot control member 102 itself or may be provided on an additional member 122 as shown in FIG. 2. The plurality of teeth 112 is adapted to engage with the interconnecting linkage means. Further, the foot control member 102 includes at least two step pads 108a and 108b defined in second end 102b of the foot control member 102 for applying a predetermined force to move the foot control member 102 in at least one of the forward position and the backward position. The predetermined force is applied by an operator’s foot in accordance with the direction and speed requirements of the vehicle. The step pad 108a is referred as forward step pad in this description. Similarly the step pad 108b is referred as backward step pad in this description. The control linkage mechanism 100 further includes at least one connecting member 118 disposed between the first connecting link member 106 and the cam connecting link member 120. Further an additional spring may be connected between the first connecting link member 106 and the foot control member 102.
[0025] FIGS. 2 and 3 depict a perspective view of a locking mechanism of the control linkage mechanism, according to a first embodiment of the invention as disclosed herein. The control linkage mechanism 100 for the hydro-static transmission unit of the vehicle includes a locking mechanism. The locking mechanism includes the hand control lever 104 operatively connected to the foot control member 102 by the interconnecting linkage means. The hand control lever 104 is configured to lock and unlock the foot control member 102 from at least one of forward position and backward position. The hand control lever 104 is disposed near the operator’s hand. During the start of the hydrostatic transmission of the vehicle the hand control lever 104 is moved to an open position. At open position, the hand control lever 104 unlocks the foot control member 102 and the operator may operate at least one of the forward step pad and the backward step pad according to predetermined requirements (such as speed and direction). Once the predetermined requirements are achieved, the hand control lever 104 is shifted to the closed position. The closed position of the hand control lever 104 locks or holds the foot control member 102 at the predetermined position.
[0026] FIG. 5 depicts a perspective view of the control linkage mechanism assembled to a housing of the hydro-static transmission unit, according to a first embodiment of the invention as disclosed herein. The interconnecting linkage means is assembled to the housing of the hydro-static transmission unit as shown in FIG. 5. The control linkage mechanism 100 for the hydro-static transmission unit of the vehicle further includes the interconnecting linkage means. The interconnecting linkage means further includes the first connecting link member 106 meshing with the plurality of teeth 112 of said foot control member 102, the second connecting link member 110 extending from the from first connecting link 106 and the third connecting link member 111 extending from the second connecting link member 110. The third connecting link member 111 is connected to the hand control lever 104 by the first pivot member 114. The first connecting link member 106 includes a plurality of stopper teeth (not shown) adapted to engage with the plurality of teeth 112 of the foot control member 102 to lock the foot control member 102 at the predetermined position.
[0027] FIG. 4 depicts a perspective view of a cam roller mechanism of the control linkage mechanism, according to a first embodiment of the invention as disclosed herein. The control linkage mechanism 100 for the hydro-static transmission unit of the vehicle further includes the cam roller mechanism operatively connected to said foot control member 102 by a cam connecting link member 120. The cam roller mechanism is adapted to shift the foot control member 102 from at least one of the forward position and the backward position to the neutral position. The cam roller mechanism includes a swash lever 115 having a first end (not shown) and a second end (not shown). The first end of swash lever 115 is pivotably connected to the vehicle at a predetermined location. The second end of swash lever 115 includes a predetermined profile P. The cam roller mechanism further includes a roller configured to rotatably move within the profile P. The roller is configured to move the swash lever 115 in at least one of a first direction and a second direction. Further, the cam roller mechanism includes a roller pivot link 116 having a first arm 116a and a second arm 116b. Furthermore, the cam roller mechanism includes at least one spring 124 connected to the second arm 116b. The spring connected to the roller pivot link 116 is configured to actuate the cam roller mechanism to shift the foot control member 102 from at least one of the forward position and the backward position to the neutral position.
[0028] FIG. 6 depicts a perspective view of a locking mechanism of a control linkage mechanism for a hydro-static transmission unit of a vehicle, according to a second embodiment of the invention as disclosed herein. In second embodiment, the control linkage mechanism 100 for the hydro-static transmission unit of the vehicle includes a braking mechanism connecting the foot control member 202 with the hand control lever 204. To accommodate the braking mechanism the foot control member 202 is modified from first embodiment described above. FIG. 7 depicts a perspective view of the control linkage mechanism assembled to a housing of a hydro-static transmission unit, according to a second embodiment of the invention as disclosed herein. The foot control member 202 is pivotably mounted on the vehicle at a first axis A and includes a first end 202a having a first arm 210 adapted to connect with a first connecting link member 206 having a first end 206a and a second end 206b. The first end 206a is connected to the first arm 210 of said foot control member 202. Further, the braking mechanism includes a brake drum 212 connected to second end 206b of the first connecting link member 206. Furthermore, the braking mechanism includes a brake pad 214 engaged with the brake drum 212. The braking mechanism further includes a second connecting member 216 connecting the brake pad 214 to the hand control lever 204 through a second pivot member 218. During the start of the hydrostatic transmission of the vehicle the hand control lever 204 is moved to an open position. At open position, the hand control lever 204 unlocks the foot control member 202. The brake pad 214 is moved away from the brake drum 212 at open position while at closed position the brake pad 214 is configured to engage with the brake drum 212 thereby restricting the motion of the foot control member 202. At closed position the hand control lever 204 locks or holds the foot control member 202 at the predetermined position.
[0029] Some of the technical benefits of the invention are as follows. Less number of linkages so high linkage efficiency. Precise speed may be achieve in forward as well as reverse speed using single hand lever so productivity of operation increases. Only one foot control member and one hand control lever is used thereby completely eliminating controls, and easy to operate. Suitable for straddle platform type tractor and can be accommodated in limited space. Minimum alteration required on existing tractor.
[0030] 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 control linkage mechanism 100 for a hydro-static transmission unit of a vehicle, said control linkage mechanism 100 comprising:
a foot control member 102 mounted on said vehicle and adapted to move between a forward position and a backward position from a neutral position;
a hand control lever 104 operatively connected to said foot control member 102 by an interconnecting linkage means; and
a cam roller mechanism operatively connected to said foot control member 102 by a cam connecting link member 120,
wherein
said foot control member 102 is pivotably movable about at a first axis A and includes a first end 102a having a plurality of teeth 112 adapted to engage with interconnecting linkage means; and
said hand control lever 104 is configured to lock said foot control member 102 in at least one of forward position and backward position; and
said cam roller mechanism adapted to shift said foot control member 102 from at least one of said forward position and said backward position to said neutral position.

2. The control linkage mechanism 100 as claimed in claim 1, wherein said foot control member 102 further includes at least two step pads 108a and 108b defined in second end 102b of said foot control member 102 for applying a predetermined force to move the foot control member 102 in at least one of said forward position and said backward position.
3. The control linkage mechanism 100 as claimed in claim 1, wherein said hand control lever 104 is configured to move in at least one of an open position and closed position to unlock and lock said foot control member 102.

4. The control linkage mechanism 100 as claimed in claim 1, wherein said interconnecting linkage means includes:
a first connecting link member 106 meshing with said plurality of teeth 112 of said foot control member 102;
a second connecting link member 110 extending from said from first connecting link 106; and
a third connecting link member 111 extending from said second connecting link member 110 and connected to said hand control lever 104,
wherein
said third connecting link member 111 is connected to said hand control lever 104 through a pivot member 114.

5. The control linkage mechanism 100 as claimed in claim 1, wherein said cam roller mechanism includes:
a swash lever 115 having a first end and a second end, said first end of swash lever 115 pivotably connected to said vehicle at a predetermined location, said second end of swash lever 115 having a predetermined profile P;
a roller configured to rotatably move within the profile P, said roller configured to move the swash lever 115 in at least one of a first direction and a second direction;
a roller pivot link 116 having a first arm and a second arm; and at least one spring 124 connected to said second arm.

6. The control linkage mechanism 100 as claimed in claim 1, wherein said control linkage mechanism 100 includes at least one connecting member 118 disposed between said first connecting link member 106 and said cam connecting link member 120.

7. The control linkage mechanism 100 as claimed in claim 1, wherein said at least one spring 124 is configured to actuate said cam roller mechanism to shift said foot control member 102 from at least one of said forward position and said backward position to said neutral position.

8. A control linkage mechanism 200 for a hydro-static transmission unit of a vehicle, said control linkage mechanism 100 comprising:
a foot control member 202 mounted on said vehicle and adapted to move between a forward position and a backward position from a neutral position;
a hand control lever 204 operatively connected to said foot control member 202 by a braking mechanism; and
a cam roller mechanism operatively connected to said foot control member 202 by a connecting link member,
wherein
said foot control member 202 is pivotably mounted on said vehicle at a first axis A and includes a first end 202a having a first arm 210 adapted to connect with braking mechanism; and
said hand control lever 204 is configured to lock said foot control member 202 in at least one of forward position and backward position; and
said cam roller mechanism adapted to shift said foot control member 202 from at least one of said forward position and said backward position to said neutral position.

9. The control linkage mechanism 100 as claimed in claim 8, wherein said braking mechanism includes:
a first connecting link member 206 having a first end 206a and a second end 206b, said first end 206a is connected to said first arm 210 of said foot control member 202;
a brake drum 212 connected to second end of said first connecting link member 206;
a brake pad 214 engaged with said brake drum 212; and
a second connecting member 216 connecting said brake pad 214 to said hand control lever 204 through a second pivot member 218.