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

COMPLETE SPECIFICATION
(SEE MEMBER 10 AND RULE 13)

TITLE OF THE INVENTION

“A SHIFTER ASSEMBLY FOR CHANGING SPEED IN WORK VEHICLES”

APPLICANTS:

Name : Mahindra &Mahindra Ltd.

Nationality : Indian

Address :Mahindra Research Valley 
Mahindra World City Plot No. 41/1 
Anjur P.O. Chengalpattu Kancheepuram
Dist  Tamilnadu.- 603204

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

[001] The present invention generally relates to a system for selecting an operating speed among plurality of speeds provided in a work machine  and particularly  relates to a shifter assembly that is adapted to work with a power take-off transmission system used with off-road vehicles such as tractors and alike to selectively shift one speed from another speed.

BACKGROUND OF THE INVENTION

[002] In general  work machine such as  for example  lathe machines  special purpose machine tools and power take-off transmission system of off road vehicles are provided with plurality of speeds to operate various machining operations and applications  wherein  the plurality of speed is obtained by disposing either plurality of gear pairs or chain drives or belt drives. In all these applications  selection of appropriate speed for the intended operation is performed by shifting one speed from another speed as per the requirement of operations. To perform this selection of a particular operating speed among plurality of speeds  a shifter assembly is incorporated with the speed transmission system of the work machine. Another aspect of the shifter assembly is that once it is shifted and positioned at a particular place  it has to be remains in that position until operator manually intervenes.

[003] In the present invention  disclosed is such a shifter assembly adapted to work with a power take-off transmission system of off road vehicles such as tractor and alike. A typical tractor assembly has a hand lever for changing speed of transmission at output shaft thereof  another hand lever for changing range of the speed of the transmission system  yet another hand lever of changing speed of power take-off transmission system  a Position Control & Draft Control quadrant assembly to operate hydraulic system of the vehicle thereby to actuate three point linkage  a foot pedal for locking differential mechanism and a hand lever for applying brake during the parking of the vehicle. All the aforesaid control levers and pedals are positioned around the operator seat of the vehicle which  ultimately  makes the operator console area very much congested and thereby makes the operator feel uncomfortable in handling all the levers and pedals while running the tractor. Also the operator’s entry in and exit of the vehicle is become uncomfortable as some of these levers restrict movement of operator around the seat. Mandatory requirement of these controls makes manufactures to route all these levers and pedals within the limited space available around the operator seat.

[004] In all these levers and pedals  some levers like hand levers used for changing speed and range of the transmission are being frequently operated by the operator during the running of the vehicle wherein some levers like lever used for changing speed of power take-off transmission system is being used only when the power from engine is to be availed at power take-off output shaft for operating different field application during running condition as well as during stationary condition of the vehicle.

[005] Hence  to overcome the aforesaid problem  levers like power take-off transmission speed changing lever is improved into a shifter according to the present invention which is designed in such a way to utilize very less amount of space around the operator seat thereby to give more space to the manufactures to accommodate other levers and pedals conveniently and comfortably without getting disturbed with other surrounding parts  and which in turn makes the operator to move around the seat very comfortably.

SUMMARY OF THE INVENTION

[006] A shifter assembly according to one aspect of the present invention comprises a shifting rod that is disposed in a vertical plane with respect to central axis of a power take-off output shaft having a first end facing downward is coupled with a pair of fork arm to engage with a dog clutch  wherein the dog clutch is disposed between a first driven gear and a second driven gear to selectively engage one of the first and second driven gear as the shifting rod is operated to transfer engine power from a power take-off input shaft to a power take-off output shaft to avail required speed at free end of the power take-off output shaft for the desired application. Second end of the shifting rod facing upward is operably coupled with a first end of a shifting arm to operate the shifting rod; second end of said shifting arm is associated with a detent mechanism to ensure proper engagement of the dog clutch with a first and second cog rings and further to arrest movement of the shifting arm once it is positioned at an operating place.

[007] The detent mechanism comprises a plate having first end provided with a hole adapted to freely receive the second end of the shifting rod and a second end provided with a first detent hole  a second detent hole and a third detent hole radially and serially arranged with reference to central axis of the hole adapted to engage with a plunger. The plate is positioned in a housing via a dowel with reference to the shifting rod to ensure proper alignment of the detent holes to engage with the plunger and rigidly secured with the housing via fastening device such as bolt and .

[008] The first end of said shifting arm having a first cylindrical extension provided with a bore having diameter adapted to freely receive the second end of the shifting rod and said shifting arm is being assembled with the second end of the shifting rod in such a way to abut the first cylindrical extension with the plate via a fastening device such as roll pin. The second end of the shifting arm is provided with a second cylindrical extension having a hollow portion  wherein the hollow portion includes a first diameter at free end of the second cylindrical extension adapted to receive a spring and a second diameter at base end of the second cylindrical extension adapted to receive a shank of said plunger as such said plunger is incorporated inside the second cylindrical extension at the second end of the shifting arm against the spring force.

[009] First end of the shank of the plunger has an extension radially outward of the shank adapted to freely slide over the first diameter of the second cylindrical extension and has a cylindrical extension axially downward having a diameter adapted to freely engage with the detent holes and second end of the shank is provided with a cylindrical rod adapted to threadingly receive a handle (148).

[010] Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However  it should be understood that the detailed description and specific examples  while indicating preferred embodiments of the invention  are given by way of illustration only  since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[011] The present invention will become more fully understood from the detailed description given herein below with reference to the accompanying drawings  and the drawings which are shown herein are just for the illustration purpose  not for limiting the scope of the present invention:

[012] FIG. 1 is a perspective view of a power take-off transmission system incorporating a shifter assembly according to the present invention.

[013] FIG. 2 is an exposed view of power take-off transmission system of FIG.1 showing the power take-off drive arrangement in relation with the shifter assembly.

[014] FIG. 3 is a top elevation of the power take-off drive arrangement of FIG.2 showing engagement of the shifter assembly with the power take-off drive arrangement.

[015] FIG. 4 is a perspective view of the shifter assembly of FIG. 2 according to the present invention.

[016] FIG. 5 is a sectional view of the shifter assembly of FIG. 3 disposed with a detent mechanism according to the present invention.

[017] FIG. 6 is an enlarged view of an elongated plate associated with the detent mechanism of the shifter assembly of FIG. 3 showing plurality of holes provided therein.

DETAILED DESCRIPTION OF THE INVENTION

[018] As the present invention is disposed of embodiments in many different forms  the detailed description of the preferred embodiments and the corresponding drawings shown herein below are to be understood that the present disclosure is an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below  like reference numerals are used to describe the same  similar or corresponding parts in the several views of FIG 1- 5
[019] Referring to FIG. 1  a power take-off transmission system (100) of an off road vehicle such as tractors and alike is mounted at rear end of the vehicle. The position of the power take-off transmission system (100)  in tractor  is varied with respect to the various configuration of the vehicle and requirement of diverse field operations as well as other field applications. Hence  a person having skilled in the art should be able to produce the invention described herein below with minor or no modification for various applications. The position of the power take-off transmission system (100) described herein is for the illustration of the working of the present invention in relation therewith and not intend to limit the scope of the present invention. The power take-off transmission system (100) comprises a housing (101) for enclosing a power take-off drive arrangement (102). Said power take-off drive arrangement (102) receives engine power through a power take-off input shaft (103) and transfer the power at the end of a power take-off output shaft (104) (104). The power take-off transmission system (100) is mounted at the rear end of a transmission case through the housing (101) via bolting means. The power take-off transmission system (100) described herein encloses the power take-off drive arrangement (102) having two speeds  however  it is to be understood that the present invention described herein below shall be adapted with a power take-off transmission system having plurality of speeds with less or no modification therein and hence the power take-off transmission system (100) disclosed herein should not be treated as limitative of the present invention.

[020] A shifter assembly (105) according to the present invention is incorporated with the power take-off transmission system (100)  wherein the shifter assembly (105) is disposed at top surface of the housing (101) and at the proximity of operator seat to comfortably operate the power take-off transmission system (100) by operator during the running condition as well as during stationary condition of the vehicle.

[021] Referring to FIG. 2  said power take-off input shaft (103) is integrally formed with a first drive gear (106) and a second drive gear (107) and rotatably supported with the housing (101) via bearings (108) at both ends of the power take-off input shaft (103). Forward end of the power take-off input shaft (103) is provided with splines to couple with an engine power drive shaft (not shown) to receive the engine power. Said first drive gear (106) is constantly meshed with a first driven gear (109) and said second drive gear (107) is constantly meshed with a second driven gear (110)  wherein said first driven gear (109) and second driven gear (110) is rotatably supported on the power take-off output shaft (104)  wherein the power take-off output shaft (104) is rotatably supported with the housing (101) via bearings (111) at both end thereof.

[022] Referring to FIG. 3  a cog wheel (not shown) is disposed between the first driven gear (109) and the second driven gear (110) and fixedly engaged with the power take-off output shaft (104) via splines. A dog clutch (112) is meshed with the cog wheel and made movable left and right of the cog wheel in the axial direction thereof. Said first driven gear (109) is integrally formed with a first cog ring (113) at the surface facing towards the cog wheel and the second driven gear (110) is integrally formed with a second cog ring (114) at the surface facing towards the cog wheel  wherein both the first cog ring (113) and the second cog ring (114) is adapted to engage with the dog clutch (112). Thus  when the dog clutch (112) engages the first cog ring (113) and the cog wheel  the engine power is transferred from the power take-off input shaft (103) to the power take-off output shaft (104) via first driven gear (109) and accordingly the power take-off output shaft (104) rotate at a first speed  and when the dog clutch (112) engages the second cog ring (114) and the cog wheel  the engine power is transferred from the power take-off input shaft (103) to the power take-off output shaft (104) via second driven gear (110) and accordingly the power take-off output shaft (104) rotate at a second speed.

[023] Referring to FIG. 4 & FIG. 5  the shifter assembly (105) according to the present invention is described herein below in details with respect to the construction and working method. The shifter assembly (105) comprises a shifting rod (115) that is disposed in a vertical plane with respect to central axis of the power take-off output shaft (104) having a first end (116) facing downward is coupled with a pair of fork arm (117) to engage with the dog clutch (112)  wherein the dog clutch (112) is disposed between the first driven gear (109) and the second driven gear (110) to selectively engage one of the first and second driven gears (109  110) with the power take-off output shaft (104) to avail corresponding speed at free end of the power take-off output shaft (104) for the desired application. Both the fork arms (117) are being secured with the shifting rod (115) via roll pins (118) to firmly engage with the dog clutch (112). Second end (119) of the shifting rod (115) facing upward is operatively secured with a shifting arm (120) perpendicularly to the axis of the shifting rod (115) to operate the shifting rod (115). An oil seal (121) is disposed at the second end (119) of the shifting rod (115) to restrict oil flow out of the housing (101) as the shifting rod (115) is inserted through the housing (101). It is to be understood that a skilled person in the art can reproduce the shifter assembly (105) of this invention in desired plane with respect to the power take-off output shaft (104) and the shifting arm (120) shall be secured radially to the axis of the shifting arm (120) to suit with the position of the power take-off transmission system (100) and the orientation of the housing (101)  and hence the orientation of the shifting rod (115) and the shifting arm (120) of this disclosure should not be deemed as limitative of the scope of the present invention. Said shifting arm (120) is associated with a detent mechanism (122) to ensure proper engagement of the dog clutch (112) with the cog rings (113  114) and further to arrest movement of the shifting arm (120) once it is positioned at an operating place.

[024] Referring to FIG. 5 & FIG. 6  the detent mechanism (122) comprises an elongated plate (123) having a first end (124) provided with a through hole (125) adapted to freely and rotatably receive the second end (119) of the shifting rod (115) and second end (126) is having a first detent hole (127)  a second detent hole (128) and a third detent hole (129) radially and serially arranged with reference to central axis of the hole (125) receives the shifting rod (115). A first through hole (130) is provided along the mid of the plate (123) adapted to receive a bolt (131) to rigidly fix the plate (123) with the housing (101) and a second through hole (132) is provided along the mid of the plate (123) to receive a dowel (133) with very close tolerance to locate the plate (123) in the housing (101) with reference to the shifting rod (115). The shifting arm (120) has a first end (134) having a first cylindrical extension (135) provided with a bore (136) having diameter adapted to freely receive the second end (119) of the shifting rod (115). The first cylindrical extension (135) is being assembled onto the second end (119) of the shifting rod (115) as such to abut the first cylindrical extension (135) with the plate (123) and thereupon rigidly secure with a roll pin (137). Second end (138) of the shifting arm (120) is provided with a second cylindrical extension (139) having a hollow portion  wherein the hollow portion includes a first diameter (140) at free end of the second cylindrical extension (139) adapted to receive a spring (141) and a second diameter (142) at base end of the second cylindrical extension (139) adapted to receive a shank (143) of a plunger (144). Said plunger (144) is vertically oriented at the second cylindrical extension (139) at the second end (138) of the shifting arm (120) and biased with said spring (141). First end of the shank (143) of the plunger (144) facing downward has an extension (145) radially outward of the shank (143) that has an diameter adapted to freely slide over the first diameter (140) of the second cylindrical extension (139) and further has an cylindrical extension (146) axially downward having a diameter relatively smaller than the shank diameter adapted to freely engage with one of the three detent holes (127  128  129) during normal condition of the shifter assembly (105). Second end facing upward of the shank (143) is formed as a cylindrical rod (147) adapted to threadingly receive a handle (148) to comfortably hold the plunger (144) to operate the shifter (105). Optionally  the cylindrical extension of the shank of the plunger shall be of an extension of any cross section which is adaptable with to engage with inner contour of the detent holes. When the shifting arm (120) is assembled onto the shifting rod (115)  free end of the second cylindrical extension (139) is adapted to abut with surface of the plate (123).

[025] Referring to FIG. 3 & FIG. 6  method of working of the shifter assembly (105) according to the present invention is described in detail herein below. When the power take-off transmission system (100) is in neutral condition  the cylindrical extension (146) of the shank (143) of the plunger (144) is engaged with the second detent hole (128) provided in the plate (123) of the detent mechanism (122) due to compressive force of the spring (141). The spring is a compression spring which is being accommodated inside the hollow portion of the second cylindrical extension (139) in such a way to be possessed with some amount of strain energy sufficiently enough to keep the plunger always engaged with any one of the detent holes (127  128  129). To select the first speed at the power take-off output shaft (104)  the plunger (144) is pulled upward by holding the handle (148) to disengage the cylindrical extension (146) from the previously engaged detent hole and rotate the shifting arm (120) in anticlockwise direction to engage the plunger (144) with the first detent hole (127)  which in turn tilt the shifting rod (115) to shift the dog clutch (112) leftward and thereby to engage the first cog ring (113) of the first driven gear (109) with the cog wheel to transfer the power from the power take-off input shaft (103) to the power take-off output shaft (104). To select the second speed at the power take-off output shaft (104)  the plunger (144) is pulled upward to rotate the shifting arm (120) in clockwise direction to engage the plunger (144) with the third detent hole (129)  which in turn tilt the shifting rod (115) to shift the dog clutch (112) rightward and thereby to engage the second cog ring (114) of the second driven gear (110) with the cog wheel to transfer the power from the power take-off input shaft (103) to the power take-off output shaft (104). It is to be understood from the present disclosure that the shifter assembly according to the present invention shall be adapted with a power take-off transmission system having plurality of speed by providing corresponding number of detent holes in the plate without any modification or with less modification within the scope of the present invention  and also the detent holes shall be of a depression on surface of the plate adapted to engage with the plunger  and hence the description of the embodiments shown herein regarding the subject feature should not be considered as limitative of the present invention.

[026] The invention being thus described  it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as departure from the spirit and scope of the invention  and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

CLAIMS
We claim:
1) A shifter assembly for changing speed of a power take-off transmission system used with off road vehicles comprises a shifting rod having a first end operably coupled with a pair of fork arms to engage with a dog clutch disposed between a plurality of driven gears thereby to selectively engage driven gears as the shifting rod is operated to transfer engine power from a power take-off input shaft to a power take-off output shaft  characterized in that

said shifting rod has a second end (119) operably coupled with a first end (134) of a shifting arm (120)  second end (138) of said shifting arm (120) is associated with a detent mechanism (122);

said detent mechanism comprises a plate (123) having plurality of depression on upper surface thereof adapted to engage with a plunger (144)  said plunger (144) is incorporated at second end of the shifting arm against a spring force.

2) The shifter assembly as claimed in claim 1  wherein the first end (134) of said shifting arm (120) having a first cylindrical extension (135) provided with a bore (136) having diameter adapted to freely receive the second end (119) of the shifting rod (115)  said shifting arm (120) is being assembled with the second end (119) of the shifting rod (115) in such a way to abut the first cylindrical extension (135) with the plate (123) via a fastening device.

3) The shifter assembly as claimed in claim 2  wherein said fastening device is a roll pin.

4) The shifter assembly as claimed in claim 1  wherein the second end (138) of the shifting arm (120) is provided with a second cylindrical extension (139) having a hollow portion  wherein the hollow portion includes a first diameter (140) at free end of the second cylindrical extension (139) adapted to receive said spring (141) and a second diameter (142) at base end of the second cylindrical extension (139) adapted to receive a shank (143) of said plunger (144).

5) The shifter assembly as claimed in claim 1  wherein the plate (123) having a first end (124) provided with a hole (125) adapted to freely receive the second end (119) of the shifting rod (115) and a second end (126) has the plurality of depressions.

6) The shifter assembly as claimed in claim 1  wherein the plate (123) is positioned in a housing (101) via a dowel (133) with reference to the shifting rod (115) to ensure proper alignment of the plurality of depression to engage with the plunger (144) and rigidly secured with the housing (101) via a fastening device.

7) The shifter assembly as claimed in claim 1  wherein said fastening device is a bolt (131).

8) The shifter assembly as claimed in claim 4  wherein first end of the shank (143) of the plunger (144) has an extension (145) radially outward of the shank (143) adapted to freely slide over the first diameter (140) of the second cylindrical extension (139) and has a projection axially downward adapted to freely engage with the plurality of depressions  wherein second end of the shank (143) is provided with a cylindrical rod (147) adapted to threadingly receive a handle (148).

9) The shifter assembly as claimed in claim 6  wherein the plurality of depressions include a first detent hole (127)  a second detent hole (128) and a third detent hole (129) radially and serially arranged with reference to central axis of the hole (125).

10) The shifter assembly as claimed in claim 5  wherein the projection is a cylindrical extension (146) having a diameter adapted to freely engage with the detent holes (127  128  129).

Date: 31st July  2012 Signature

Dr.Kalyan Chakravarthy
Patent Agent

ABSTRACT
A shifter assembly for changing speeds of a power take-off transmission system used with off road vehicles. The shifter assembly includes a shifting rod having a first end operably coupled with a pair of fork arms to engage with a dog clutch disposed between a plurality of driven gear thereby to selectively engage driven gears as the shifting rod is operated to transfer engine power from a power take-off input shaft to a power take-off output shaft. Further  the shifting rod includes a second end operably coupled with a first end of a shifting arm  second end of the shifting arm is associated with a detent mechanism. The detent mechanism comprises a plate having plurality of depression on upper surface thereof adapted to engage with a plunger  the plunger is incorporated at second end of the shifting arm against a spring force.
Fig. 1