Title of Invention

A GEAR SHIFT INTERLOCK MECHANISM FOR A MULTISPEED SYNCHROMESH TRANSMISSION SYSTEM

Abstract A gear shift interlock mechanism for locking the inactive shifter shafts of a multispeed synchromesh transmission system when the desired shifter shaft is actuated,comprising symmertric left and right interlock arms accommodated in a housing;a pivot pin fastened to the housing and passingt through the interlock arm to procid a swivelling act5ion;each shifter shaft being provide3d with a groove for seating the interlock arms;top and bottom return springs for bring the interlock arms to their respective neutral positions,said interlock arms,in their neutral positions resting in the centre of the shifter shafts without direct contact with the said shafts.
Full Text

The present invention relates to a gear shift interlock mechanism for a multi-speed synchromesh transmission system using two interlock arms to lock the inactive shifter shafts when the desired shifter shaft is actuated.
The function of the known gearbox is to alter the available torque and speed of the engine according to requirement and then pass it to the other components of the drive train. The synchromesh gearbox has two sets of gears, which are in constant mesh. They are the drive gears on the input shaft, which get their drive for the output of the engine and the driven gears of the counter shaft that are driven by the input shaft gears. Although the two shaft assemblies are in constant mesh the appropriate speed ratio is selected by the driver by moving the shifter sleeve of the synchronizer unit and engaging it with the desired gear. The movement of the shifter shaft is in linear direction only. Three shifter shafts are used for shifting the gears. They move from mean position or neutral position towards the chosen gear. The internal shift mechanism has a shift select assembly that helps to select the desired plane and gear. An interlock mechanism is used to lock the remaining 2 shifter shafts in neutral position when the desired gear is engaged. The known interlock mechanism consists of an interlock plate, gear shift/select lever, shift/select shaft, interlock bolt, E-rings and spring pin. This mechanism is driven by the external shift mechanism, which is actuated by the driver. There are no interlock grooves on the shifter shafts.
Fig.l of the accompanying drawings illustrates the gear shift interlock mechanism in a typical 5 speed gear box with 3 shifter shafts SSI SS2
SS3.Yokes Yl Y2 Y3 are fastened to the shifter shafts respectively. The

gear shift/select mechanism consisting of shift/select shaft SSS interlock plate IP interlock bolt IB is connected to the shifting mechanism on one side and actuates the yokes Yl Y2 Y3 on the other side. The interlock plate IP is placed in the center of the yokes Yl Y2 Y3. There is a provision in the interlock plate IP for the axial movement of one yoke at a time. When the driver operates the external gear shift meachnism to shift a gear the external gear shift m each an ism operates the shift/select shaft SSS to select and shift the descired gear. When the shift/select shaft SSS moves axially the shift plane is selected. The slot provided in the interlock plate IP allows the yoke to move towards the gear to be engaged. When the gear shift/select shaft rotates at an angle the desired gear is engaged. The interlock plate IP rests in the groove of the other two yokes and restricts their movement. Thus it is seen that only one shaft moves at a time.
In the known system the major drawback is the large number of components required for the functioning of the interlock mechanism. This increases the assembly and dismantling time.
To cope with the above problem, it is proposed to reduce the number of components and make the mechanism more simple, but with an ability to perform the same function of efficiently locking the idle shifter shafts in neutral position.
This invention proposes a simple mechanism, which is independent of the shift/select mechanism.

The interlock mechanism for locking the inactive shifter shafts of a multispeed synchromesh transmission system, when the desired shifter shaft is actuated, according to this invention, comprises symmetric left and right interlock arms accommodated in a housing; a pivot pin fastened to the housing and passing through the interlock arm to provide a swivelling action; top and bottom return springs for bringing the interlock arms to their respective neutral positions, said interlock arms, in their neutral positions resting in the centre of the shifter shafts without direct contact with the said shafts.
This invention will now be described with reference to the accompanying drawings which illustrate by way of example, and not by way of limitation, one of possible embodiments of the interlock mechanism proposed herein,
Fig 1 illustrating the gear shift interlock mechanism in a typical 5 speed
gear box with 3 shifter shafts.
Fig. 2 illustrating the construction of the said embodiment
Fig. 3 illustrating the said embodiment in neutral position.
Fig. 4 illustrating the said embodiment in action when the second shifter
shaft SS2 is engaged.
Fig. 5 illustrating the front view of the said embodiment in the central shaft
engaged position.
Fig. 6 illustrating the said embodiment in the first shifter shaft (SSI) in the
engaged position.

A reference to Fig. 1 has already been made hereinabove.
Referring to fig.2 for the construction of the interlock mechanism, the driver via the external shift mechanism and internal shift mechanism actuates the shifter shafts (SSI, SS2 and SS3). The shifter shafts SSI SS2 SS3 have grooves Gl G2 and G3 machined in it for seating the interlock arms RIA and LIA. The interlock mechanism consists of 2 interlock arms for the purpose of differentiation and are called "right interlock arm" RIA and "left interlock arm" LIA. Both interlock arms are symmetric in construction except for the orientation of the return spring holding pins RP1 and RP1. Two pivot pins PP1 and PP2 are fastened to the housing and pass through the interlock arms RIA and LIA to provide the swiveling action. Two springs which are the top return springs TS and the bottom return spring BS are provided to bring the interlock arms RIA LIA to their respective positions in neutral condition. In neutral condition the interlock arms rest in the center of the shifter shafts SSI SS2 SS3 without having direct contact with the shaft itself.
Fig. 3 illustrates the gear shift interlock mechanism in neutral position. The preloaded return springs TS and BS placed at the top and bottom of the interlock arms RIA and LIA hold the interlock arms in a position such that they do not have contact with any of the shifter shafts SSI SS2 SS3. The interlock arms RIA and LIA swivel about the pivot pin PP1 and PP2 axis.
P»8: 4 Illustrates the interlock mechanism In action when the second shliter shaft SS2 is engaged- When the driver operates the second shifter shaft

SS2 the right interlock arm RIA and the left interlock arm LIA are pushed upwards against the return spring TS force when they are forced out of the machined groove G2 in the shifter shaft SS2. Since there are pivot pins PP1 and PP2 in the interlock arms RIA and LIA the interlock arms rotate about the axis of the pivot pins PP1 and PP2. At this time the extreme end of the right interlock arm RIA touches the base of the machined groove Gl of the shifter shaft SSL The same happens with the left interlock arm LIA as it falls into the machined groove G3 of the side shifter shaft SS3.
Fig. 5 shows the front view of the interlock mechanism in the central shaft engaged position.
When the central shifter shaft SS2 is shifted back to the neutral position all the components return to their respective neutral positions. This is ensured by the return springs TS and BS.
Fig. 6 shows the gear shift interlock mechanism in the first shifter shaft SSI engaged position. When the shifter shaft SSI is moved linearly, the end of the right interlock arm RIA is forced out of machined groove Gl of the shifter shaft SSL The right interlock arm RIArotates about the pivot pin PP1 thus locking the shifter shaft SS2 in the machined groove G2. The extended portion of the arm RIA which has the retainer pin RPlfor the top return spring TS pushes the extended arm of the left interlock arm LIA and causes the left interlock arm to swivel about the pivot pin axis PP2. Thus it locks the shifter shaft SS3 in the machined groove G3. The return springs TS and BS are expanded during this operation.

When the shifter shaft SSI is shifted back to the neutral position all the components return to their respective neutral positions. This is ensured by the return springs.
Fig. 7 shows the front view of the gear shift interlock mechanism in the shifter shaft SSI engaged position.
The operation is similar when the shifter shaft SS3 is actuated. The left interlock arm LIA is pushed upward during the operation.
The earlier system uses a mechanism, which is complicated in assembling and dismantling increasing the assembly time. This invention uses a simple swivel mechanism consisting of less number of components thus reducing the part count. This system is fool proof because both the arms are partially inside the machined grooves of the shifter shaft, thus eliminating the possibility of engagement of all three or any two shafts at a time.
The terms and expressions herein are of description and not of limitation, since various other embodiments of this invention are possible within the scope and ambit of this invention.





We Claim:
1. A gear shift interlock mechanism for locking the inactive
shifter shafts of a multispeed synchromesh transmission
system, when the desired shifter shaft is actuated,
comprising symmetric left and right interlock arms
accommodated in a housing; a pivot pin fastened to the
housing and passing through the interlock arm to provide a
swivelling action; each shifter shaft being provided with a
groove for seating the interlock arms: top and bottom return
springs for bringing the interlock arms to their respective
neutral positions, said interlock arms, in their neutral
positions resting in the centre of the shifter shafts without
direct contact with the said shafts.
2. A gear shift interlock mechanism for locking the inactive
shifter shafts of a multispeed synchromesh transmission
system substantially as herein described and illustrated.


Documents:

585-che-2004-abstract.pdf

585-che-2004-claims duplicate.pdf

585-che-2004-claims original.pdf

585-che-2004-correspondnece-others.pdf

585-che-2004-correspondnece-po.pdf

585-che-2004-description(complete) duplicate.pdf

585-che-2004-description(complete) original.pdf

585-che-2004-drawings.pdf

585-che-2004-form 1.pdf

585-che-2004-form 26.pdf

585-che-2004-other document.pdf


Patent Number 205193
Indian Patent Application Number 585/CHE/2004
PG Journal Number 26/2007
Publication Date 29-Jun-2007
Grant Date 22-Mar-2007
Date of Filing 18-Jun-2004
Name of Patentee M/S. TVS MOTOR COMPANY LIMITED
Applicant Address JAYALAKSHMI ESTATES NO,8,HADDOWS ROAD,CHENNAI-600 006
Inventors:
# Inventor's Name Inventor's Address
1 SANDEEP D'MELLO TVS MOTOR COMPANY LIMITED JAYALAKSHMI ESTATES NO,8,HADDOWS ROAD,CHENNAI-600 006
2 tirupati muni manoz kumar TVS MOTOR COMPANY LIMITED JAYALAKSHMI ESTATES NO,8,HADDOWS ROAD,CHENNAI-600 006
3 vinayak dattatraya kathare TVS MOTOR COMPANY LIMITED JAYALAKSHMI ESTATES NO,8,HADDOWS ROAD,CHENNAI-600 006
PCT International Classification Number B 62 D 63/08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA