FORM 2
THE PATENT ACT 1970 (as amended)
[39 OF 1970]
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
[See Section 10 and Rule 13]
TITLE: “A GEARBOX COMPRISING RANGE INTERLOCK MECHANISM, A METHOD OF INTERLOCKING AND A METHOD OF ASSEMBLING
THEREOF”
NAME AND ADDRESS OF THE APPLICANT: TATA MOTORS LIMITED, an Indian company having its registered office at Bombay house, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001, Maharashtra, INDIA.
Nationality: INDIAN
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

TECHNICAL FIELD
Embodiment of the disclosure is related to heavy commercial vehicles comprising gearboxes of split type gears or planetary gearbox system along with a main speed gearbox. The planetary gearbox system along with the main gearbox is used to shift from low range to high range and from high range to low range.
BACKGROUND OF THE DISCLOSURE AND PRIOR ARTS
Range is a planetary gearbox construction having two or more gear ratios. The total gear ratio output in heavy commercial gearboxes is a multiplication of gear ratio of the main gearbox and gear ratio of the range gearbox. Generally, total lower gear ratios such as for gears 1, 2, 3 & 4 in an 8 speed gearbox utilize low range gear ratio. To shift from the 4th gear to the 5th gear, the range gear is also required to be shifted from low gear (referred as low range) to high gear (referred as high range). In addition, while shifting down from the higher gears such as 8, 7, 6, 5, and below, shifting from 5th gear to 4th gear requires change from high range to low range in the range gearbox.
The change from high range to low range in the range gearbox is executed with the help of a pneumatic cylinder [range shifting cylinder (6)]. The range shifting cylinder (6) having a piston carries a shifter fork (9). Speeds of an output shaft of the complete gearbox and range gears are synchronized by range synchronizers (8). The low range synchronizers absorb more energy when compared to the high range synchronizers due to higher reflected inertia and higher speeds of shifting while shifting from the high range to the low range. During this process of shifting from the high range to the low range, the low range synchronizers are more prone to damage. Hence, users/drivers of the vehicles are instructed to shift to the low range only at a certain vehicle speed and not when the vehicle is more than the predetermined threshold speed. The instructions given to users/drivers are seldom followed by the users/drivers due to negligence or demand of any particular situation. Thus, the low range synchronizers are prone to cause clashing on the range gearbox while shifting from the high range to the low range.
Conventional heavy commercial vehicle gearbox with range gearbox and a main gearbox is shown in Figure 1. Here, range shifting is actuated in the top cover (3) of the main

gearbox (1). The top cover (3) contains a selection shaft (9) and a range shift control valve (4) bolted to the top cover (3). Air is passed through the range shifting control valve (4) to a range shift cylinder (6) via a plurality of pneumatic lines (5a and 5b). A range shifter shaft (7) is connected to a piston of the range shift cylinder (6). A range shifter fork (8) is used for changing the range.
During shifting of range from the low range to the high range, the selection shaft (9) is to be actuated by the user/driver which in turn actuates the range shifting control valve (4). The actuation of the range shifting control valve (4) passes air supplied from an air cylinder of vehicle to the range shift cylinder (6) through the pneumatic line (5a). Thus the range shifter cylinder (6) retracts the range shifter shaft (7) for engaging the range at the high range.
Similarly, while shifting from the high range to the low range, the range shifting control valve (4) is actuated by the selection shaft (9) actuated by the user/driver to pass the air supplied from the air cylinder of the vehicle to the range shift cylinder (6) through the pneumatic line (5b). Thus the range shift cylinder (6) pushes the range shifter shaft (7) for engaging the range at the low range.
In the existing gearbox system, the user/driver is shifting from high range to low range at his will. Even though the users/drivers are trained and instructed to shift to the low range only when predetermined threshold vehicle speed is achieved, the users/drivers are used to shift range from the high range to the low range at higher vehicle speeds without applying brakes or without monitoring the speed of vehicle to a predetermined threshold vehicle speed. Due to this practice, while shifting to the low range the synchrocones/synchronizers of the vehicle are forced to absorb huge amount of kinetic energy in order to synchronize the low range at very high vehicle speeds. This causes damage to the synchrocones at early stages and fail.
Referring now to Figure 2, the spool (15) of the range shifting control valve (4) is in outward condition. This allows the air to pass through the range shifting control valve (4) to port connected to the pneumatic line (5a) for engaging the high range.

Referring now to Figure 3, the spool (15) of the range shifting control valve (4) is pressed inside by the movement of the selection shaft (9). This allows the air to pass through the range shifting control valve (4) to port connected to the pneumatic line (5b) for engaging the low range.
In order to prevent and protect the low range synchronizers from faulty or mishandled shifting from the high range to the low range, an interlock mechanism for the low range shifting is provided in the disclosure. The interlock mechanism allows the user/driver to shift to the low range only when the vehicle speed is below the predetermined threshold value.
OBJECTS OF THE DISCLOSURE
The object is to provide an interlocking mechanism for a gearbox (A) to prevent shifting of high range gear to low range gear when the vehicle speed is more than predetermined threshold speed.
The object is to prevent damages to low range synchronizers from faulty or mishandled shifting of range from high range to low range.
STATEMENT OF THE DISCLOSURE
Accordingly, the disclosure relates to a gearbox (A), comprising a main gearbox (1) consisting of a top cover (3) and a selection shaft (9); a range gearbox (2) connected to the main gearbox (1); a range shifting control valve (4) connected to the top cover (3); an interlock mechanism (10) connected to the range shifting control valve (4) at one end and other end is connected to a solenoid valve (13); the solenoid valve (13) connected to an Engine Control Unit (14) (ECU) of a vehicle; wherein said solenoid valve (13) is actuated to pass air to the interlock mechanism (10) using signals of the ECU during gear shifting operation to prevent shifting of high range gear to low range gear when the vehicle speed is more than predetermined threshold speed, also relates to a method of interlocking selection shaft (9) of a gearbox during gear shifting operation to prevent shifting of high range gear to low range gear when the vehicle speed is more than predetermined threshold speed, said method comprising acts of sensing speed of the vehicle by ECU

(14); actuating a solenoid valve (13) by the ECU when the speed of vehicle is more than predetermined threshold speed; applying pressure of air onto a diaphragm (11) of the interlock mechanism (10) by the actuated solenoid valve (13) to displace a spool (15) axially; wherein said displaced spool (15) contacts a selection shaft (9) and blocks movement of the selection shaft (9) during gear shifting operation to prevent shifting of current high range gear to low range gear, and also relates to a method of assembling a gearbox, said method comprising acts of connecting a main gearbox (1) comprising a top cover (3) and a selection shaft (9) to a range gearbox (2); connecting an interlock mechanism (10) to the range shifting control valve (4) at one end and other end is connected to a solenoid valve (13); connecting the solenoid valve (13) to an Engine Control Unit (14) (ECU) of a vehicle.
SUMMARY
In one embodiment of the disclosure, a gearbox, comprising a main gearbox (1) consisting of a top cover (3) and a selection shaft (9); a range gearbox (2) connected to the main gearbox (1); a range shifting control valve (4) connected to the top cover (3); an interlock mechanism (10) connected to the range shifting control valve (4) at one end and other end is connected to a solenoid valve (13); the solenoid valve (13) connected to an Engine Control Unit (14) (ECU) of a vehicle; wherein said solenoid valve (13) is actuated to pass air to the interlock mechanism (10) using signals of the ECU during gear shifting operation to prevent shifting of current high range gear to low range gear when the vehicle speed is more than predetermined threshold speed.
In one embodiment the range gearbox (2) consisting of a range shift cylinder (6) connected to pneumatic lines (5a, 5b); a range shifter shaft (7) connected to piston of the range shift cylinder (6); and a range shifter fork (8) attached to the range shifter shaft (7) for varying range according to speed of the vehicle.
In one embodiment, the interlock mechanism (10) consisting of a diaphragm (11) connected with a spring (16) and a port (12).

In one embodiment, the diaphragm (11) is connected to a spool (15) of the range shifting control valve (4) and is axially displaceable by pressure of air through the solenoid valve (13).
In one embodiment, the spool (15) contacts and blocks the selection shaft (9) during gear shifting operation to prevent shifting of current high range gear to low range gear when the vehicle speed is more than predetermined threshold speed.
In one embodiment of the disclosure, a method of interlocking selection shaft (9) of a gearbox during gear shifting operation to prevent shifting of current high range gear to low range gear when the vehicle speed is more than predetermined threshold speed, said method comprising acts of sensing speed of the vehicle by ECU (14); actuating a solenoid valve (13) by the ECU when the speed of vehicle is more than predetermined threshold value; applying pressure of air onto a diaphragm (11) of the interlock mechanism (10) by the actuated solenoid valve (13) to displace a spool (15) axially; wherein said displaced spool (15) contacts a selection shaft (9) and blocks movement of the selection shaft (9) during gear shifting operation to prevent shifting of current high range gear to low range gear.
In one embodiment of the disclosure, a method of assembling a gearbox, said method comprising acts of connecting a main gearbox (1) comprising a top cover (3) and a selection shaft (9) to a range gearbox (2); connecting an interlock mechanism (10) to the range shifting control valve (4) at one end and other end is connected to a solenoid valve (13); connecting the solenoid valve (13) to an Engine Control Unit (14) (ECU) of a vehicle.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example

only, with reference to the accompanying figures wherein like reference numerals
represent like elements and in which:
Figure 1: shows the outline of heavy commercial gearbox and the range shifting
mechanism embodiment according to the prior art.
Figure 2: shows sectional view of range shift valve (4) arrangement in the ‘High Range’
engaged position according to the prior art.
Figure 3: shows sectional view of range shift valve (4) arrangement in the ‘Low Range’
engaged position according to the prior art.
Figure 4: shows the outline of heavy commercial gearbox comprising high speed range
interlock mechanism according to the disclosure.
Figure 5: shows sectional view of embodiment of range shift valve (4) arrangement along
with interlock mechanism (10) in the ‘High Range’ engaged position according to the
disclosure.
Figure 6: shows sectional view of embodiment of range shift valve (4) arrangement along
with interlock mechanism (10) in the ‘Low Range’ engaged position according to the
disclosure.
Figure 7: shows sectional view of embodiment of range shift valve (4) arrangement along
with interlock mechanism (10) in locked condition, not allowing the shift from ‘High
Range’ to ‘Low Range’.
The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the accompanying figures, which form a part hereof. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, and figures are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects

of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.
This disclosure is drawn, inter-alia, to a gearbox, a method of interlocking selection shaft (9) of a gearbox during gear shifting operation, and a method of assembling the gearbox.
Referral numerals:
A: Gearbox of the heavy vehicle
1: Main gearbox
2: Range gearbox
3: Top Cover
4: Range shifting control valve
5a and 5b: Pneumatic lines
6: Range shift cylinder
7: Range shifting shaft
8: Range shifter fork
9: Selection shaft
10: Interlock mechanism
11: Diaphragm
12: Port in the interlock mechanism
13: Solenoid valve
14: Engine Control Unit (ECU) of a vehicle
15: Spool
Figure 4 illustrates the outline of heavy commercial gearbox comprising high speed range interlock mechanism according to the disclosure. Here, range shifting is actuated in the top cover (3) of the main gearbox (1). The top cover (3) contains a selection shaft (9) and a range shift control valve (4) bolted to the top cover (3). Air is passed through the range shifting control valve (4) to a range shift cylinder (6) via a plurality of pneumatic lines (5a and 5b). A range shifter shaft (7) is connected to a piston of the range shift cylinder (6). A range shifter fork (8) is used for changing the range.

A solenoid valve (13) is connected to the range shifting control valve (4) through an interlock mechanism (10) for regulating air through the pneumatic lines (5a and 5b). The solenoid valve (13) supplies air to the interlock mechanism (10) for displacing spool (15) of the range shifting control valve (4) to regulate of the air through the pneumatic lines (5a and 5b). The solenoid valve (13) is actuates by vehicle ECU (14) connected to it. The ECU is programmed to provide signals to the solenoid valve (13) when the vehicle speed is more than predetermined threshold value while shifting from high range to low range. The interlock mechanism (10) locks the abuse shifts to the low range by a non-skilled user/driver.
Figure 5 illustrates sectional view of assembly of the range shifting control valve (4) with the interlock mechanism (10) and the selection shaft (9). The vehicle is in high range position, wherein the spool (15) of the range shifting control valve (4) is in outward condition. The outward condition of the spool (15) allows the air from the air cylinder to pass through air inlet of the range shifting control valve (4) to port connected to pneumatic line (5a). The air passed through the pneumatic line (5a) activates the range shift cylinder which in turn activates the range shifter shaft (7) through a piston of the range shift cylinder (6). A range shifter fork (8) connected to the range shifter shaft (7) thus changes the range to high range position. In this condition, the shift interlock device (10) is not activated as there is no air supplied by the solenoid valve to port (12) of the interlock mechanism (10) and hence range shift is in high range position.
Figure 6 illustrates sectional view of assembly of the range shifting control valve (4) with interlock mechanism (10) and the selection shaft (9). The vehicle is in the low range position, wherein the spool (15) of the range shifting valve (9) is in inward condition by pressing force applied by the selection shaft (9). The inward condition of the spool (15) allows the air from the air cylinder to pass through the air inlet of the range shifting control valve (4) to port connected to the pneumatic line (5b). The air passed through the pneumatic line (5b) activates the range shift cylinder which in turn activates the range shifter shaft (7) through a piston of the range shift cylinder (6). A range shifter fork (8) connected to the range shifter shaft (7) thus changes the range to low range position. In this condition, the shift interlock device (10) is not activated as there is no air supplied by

the solenoid valve to port (12) of the interlock mechanism (10) and hence range shift is in low range position. The low range is engaged at specified vehicle speed or below specified vehicle speed.
Figure 7 illustrates sectional view of assembly of range shifting control valve (4) with interlocking mechanism (10) and a selection shaft (9). The selection shaft (9) is in locked condition. The locked condition doesn’t allow the range shift from high range to low range. The shift to the low range is blocked when the speed of vehicle is above the specified threshold vehicle speed for changing the shift from high range to low range. The selection shaft (9) is not allowed to move in the direction of force as the spool (15) is pushed from backside by the interlock mechanism (10). The interlock mechanism (10) is actuated by the solenoid valve (13) which in turn is actuated by ECU (14) signal. The actuated solenoid valve (3) passes air to the port (12) of the interlock mechanism (10) to push a diaphragm (11) in the interlock mechanism (10) to further push the spool (15) connected to it. Thus the spool (15) is held in that position to restrict the shift change and maintain the high range position even though the user tries to shift from high range to the low range without applying brake of the vehicle. The interlock mechanism (10) blocks abusive and non-skillful shifting from high range to low range and prevents damage to the low range synchrocones by locking the selection shaft by the interlock mechanism (10).
Equivalents
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further

understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

We claim:
1. A gearbox (A), comprising:
a main gearbox (1) consisting of a top cover (3) and a selection shaft (9);
a range gearbox (2) connected to the main gearbox (1);
a range shifting control valve (4) connected to the top cover (3);
an interlock mechanism (10) connected to the range shifting control valve (4) at one end and other end is connected to a solenoid valve (13);
the solenoid valve (13) connected to an Engine Control Unit (14) (ECU) of a vehicle;
said solenoid valve (13) is actuated to pass air to the interlock mechanism (10) using signals of the ECU during gear shifting operation to prevent shifting of current high range gear to low range gear when the vehicle speed is more than predetermined threshold speed.
2. The gearbox as claimed in claim 1, wherein the range gearbox (2) consisting of a range shift cylinder (6) connected to pneumatic lines (5a, 5b).
3. The gearbox as claimed in claim 2, wherein a range shifter shaft (7) is connected to piston of the range shift cylinder (6)
4. The gearbox as claimed in claim 3, wherein a range shifter fork (8) is attached to the range shifter shaft (7) for varying range according to speed of the vehicle.
5. The gearbox as claimed in claim 1, wherein the interlock mechanism (10) consisting of a diaphragm (11) connected with a spring (16) and a port (12).
6. The gearbox as claimed in claim 5, wherein the diaphragm (11) is connected to a spool (15) of the range shifting control valve (4) and is axially displaceable by pressure of air through the solenoid valve (13).
7. The gearbox as claimed in claim 6, wherein the spool (15) contacts and blocks the selection shaft (9) during gear shifting operation to prevent shifting of current high

range gear to low range gear when the vehicle speed is more than predetermined threshold speed.
8. A method of interlocking selection shaft (9) of a gearbox during gear shifting
operation to prevent shifting of current high range gear to low range gear when the
vehicle speed is more than predetermined threshold speed, said method comprising
acts of:
sensing speed of the vehicle by ECU (14);
actuating a solenoid valve (13) by the ECU when the speed of vehicle is more than the predetermined threshold valve;
applying pressure of air onto a diaphragm (11) of the interlock mechanism (10) by the actuated solenoid valve (13) to displace a spool (15) axially; said displaced spool (15) contacts a selection shaft (9) and blocks movement of the selection shaft (9) during gear shifting operation to prevent shifting of current high range gear to low range gear.
9. A method of assembling a gearbox (A), said method comprising acts of:
connecting a main gearbox (1) comprising a top cover (3) and a selection shaft (9) to a range gearbox (2);
connecting an interlock mechanism (10) to the range shifting control valve (4) at one end and other end is connected to a solenoid valve (13);
connecting the solenoid valve (13) to an Engine Control Unit (14) (ECU) of a vehicle.
10. A gearbox, a method of interlocking the gearbox and a method of assembling are
substantially as herein above described and as illustrated in accompanying drawings.