FIELD
The present disclosure relates to the field of gearbox, particularly manual
transmission gearbox.
BACKGROUND
The background information herein below relates to the present disclosure but is
not necessarily prior art.
Most vehicles available in the market (which includes automobiles, tractors, and
mining machines) include a gearbox assembly to facilitate operation at different
speeds and different load conditions. A clutch mechanism is provided for
facilitating a smooth transition between different gears. In accordance with
standard procedure, a driver of the automobile, tractor, and mining machine is
required to press the clutch lever and disengage clutch plates before shifting a
gear. The operation of the clutch plates facilitates smooth disengagement of an
engaged first gear and a smooth engagement of a second gear. However, some
unskilled drivers of the vehicle shift gears without completely depressing the
clutch pedal. As a result the gears are being shifted without complete
disengagement of the clutch plates. This leads to undue stresses on gearbox
components (shifting forks, lever, and gears) which may lead to failure or loss of
functionality. Such act of the driver is undesirable and may damage gear teeth
and the gearbox assembly.
Presently, gearbox assemblies are not provided with a foolproof arrangement to
restrain the driver from shifting gears without pressing the clutch pedal. The
bypassing of clutch pedal operation results in jerks and excessive stress on the
components of the gearbox assembly. Therefore, the owners of the automobile,
tractor, and mining machine have to face severe issues such as early breakdowns,
increased maintenance, and reduced useful life of the gearbox. This results in
huge economic losses.
There is, therefore, felt a need of a device, for controlling the operation of the
gear shift lever, which alleviates the aforementioned drawbacks.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment
herein satisfies, are as follows:
An object of the present disclosure is to provide a device for controlling the
operation of the gear shift lever.
Another object of the present disclosure is to provide a device for controlling the
operation of the gear shift lever that prevents bypassing of clutch mechanism by a
driver.
Yet another object of the present disclosure is to provide a device for controlling
the operation of the gear shift lever that reduces the maintenance cost and the
frequency of breakdown of the gearbox.
Still another object of the present disclosure is to provide a device for controlling
the operation of the gear shift lever that increases the useful life of the gearbox
assembly.
An object of the present disclosure is to provide a device for controlling the
operation of the gear shift lever that prevents the operation of a gear shift lever
without complete disengagement of transmission clutch.
An object of the present disclosure is to provide a device for controlling the
operation of the gear shift lever that uses simple components and mechanical
linkages.
An object of the present disclosure is to provide a device for controlling the
operation of the gear shift lever that is cost effective.
Other objects and advantages of the present disclosure will be more apparent
from the following description, which is not intended to limit the scope of the
present disclosure.
SUMMARY
The present disclosure envisages a device for controlling the operation of a gear
shift lever for a manual transmission gearbox.
In accordance with an embodiment of the present disclosure, the device for
controlling the operation of the gear shift lever comprises a device housing that
abuts a shifter rod of the gearbox. A plurality of grooves is formed on the shifter
rod, wherein the grooves are configured to be in a positive engagement with the
plunger when the plunger is in an inoperative extended position.
A mechanically actuated spring loaded plunger is free to reciprocate inside the
housing and the plunger is further configured to be normally in an extended
position. In the extended position, the plunger is in a positive engagement with
the shifter rod. A control cable is used to mechanically connect the plunger to a
clutch pedal, and the control cable configured to move the plunger to a retracted
position when the clutch pedal is operated. In the retracted position of the plunger
the shifter rod is free to move.
In another embodiment, a protruding portion is provided at a first operative end
of the plunger. The protruding portion is configured to positively engage with at
least one of the grooves of the shifter rod.
In yet another embodiment, the device for controlling the operation of the gear
shift lever includes a compression spring for retaining the plunger in the extended
position.
In an embodiment, the housing of the device is detachably fastened to gear shift
lever housing.
In another embodiment, the housing of the device is detachably fastened to
gearbox housing.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
A device for controlling the operation of the gear shift lever of the present
disclosure will now be described with the help of the accompanying drawing, in
which:
Figure 1 shows an isometric view of a device for controlling the operation of the
gear shift lever, in accordance with an embodiment of the present disclosure;
Figure 2 shows a cross sectional view of the device of Figure 1; and
Figure 3 shows a cross sectional view of a gearbox housing showing the
connection between a gear shift lever and a shifter rod.
LIST OF REFERENCE NUMERALS
102 - Gear shift lever
104-Shifter rod
104a, 104b... 104n - Grooves on shifter rod
105 - Gear shift lever housing
120- Clutch lever
150 - Device for controlling the operation of the gear shift lever
152-Plunger
152a - Protruding portion of plunger
154 - Compression spring
156 - Plunger housing
158 -Retainer
170 - Opening in the gear shift lever housing
170a - Annular base support
170b - First internal threads
171 - Cable cover
171a - First end of cable cover
171b - Second end of cable cover
172-Control cable
173 - Cable wire
173 a - Anchor of the cable wire
173b - End of the cable wire that is connected to clutch pedal
175 - Support plate
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to
the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the
present disclosure to the person skilled in the art. Numerous details, are set forth,
relating to specific components, to provide a complete understanding of
embodiments of the present disclosure. It will be apparent to the person skilled in
the art that the details provided in the embodiments should not be construed to
limit the scope of the present disclosure. In some embodiments, well-known
processes, well-known apparatus structures, and well-known techniques are not
described in detail.
The terminology used, in the present disclosure, is only for the purpose of
explaining a particular embodiment and such terminology shall not be considered
to limit the scope of the present disclosure. As used in the present disclosure, the
forms "a," "an," and "the" may be intended to include the plural forms as well,
unless the context clearly suggests otherwise. The terms "comprises,"
"comprising," "including," and "having," are open ended transitional phrases and
therefore specify the presence of stated features, operations, elements, units
and/or components, but do not forbid the presence or addition of one or more
other features, operations, elements, components, and/or groups thereof.
When an element is referred to as being "mounted on," "engaged to," "connected
to," or "coupled to" another element, it may be directly on, engaged, connected or
coupled to the other element. As used herein, the term "and/or" includes any and
all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of
the present disclosure as the aforementioned terms may be only used to
distinguish one element, component, region, or section from another component,
region, or section. Terms such as first, second, third etc., when used herein do not
imply a specific sequence or order unless clearly suggested by the present
disclosure.
Terms such as "inner," "outer," "beneath," "below," "lower," "above," "upper,"
and the like, may be used in the present disclosure to describe relationships
between different elements as depicted from the figures.
Conventional manual transmission gearboxes do not have a foolproof provision
to restrict an unskilled driver/operator from shifting a gear without depressing
clutch pedal. This practice results in huge economic losses to the owner of the
vehicles having a manual transmission gearbox.
It shall be noted that the term "vehicle" used in the description also covers the
machines such as "automobile", "tractor", "mining machines", and "agricultural
and construction machineries".
Figure 1 illustrates an isometric view of a device for controlling the operation of a
gear shift lever 102 detachably fastened, in proximity, to a shift lever housing
105, in accordance with an embodiment of the present disclosure.
In accordance with an embodiment of the present disclosure, a mechanical
plunger 152 driven from a clutch lever 120 is used to restrict the movement of the
gear shift lever 102. The plunger 152 is normally held in a positive locking
engagement with a gear shifter rod 104 unless the clutch pedal is operated by the
driver. The gear shifter rod 104 can be shifted only when there is a complete
disengagement of clutch plates of a clutch assembly, otherwise the gear shifter
rod 104 remains locked in its instant position, and the driver is unable to move
the shift lever 102. When the clutch pedal is depressed, transmission clutch is
disengaged from the engine and it is safe to shift the gear of the vehicle.
The present disclosure envisages a device 150 for controlling the operation of a
gear shift lever 102. The device 150 is described below with reference to Figure 1
and Figure 2. Figure 2 depicts a cross-sectional view of the device 150 shown in
Figure 1.
The device 150 for controlling the operation of the gear shift lever 102 that
employees a mechanical locking arrangement, is illustrated with the help of
Figure 1 and Figure 2. The manual gear shifting arrangement includes a gear shift
lever 102, shifter rod 104, a gearbox (not specifically shown in figures), and
shifting forks and gears (not specifically shown in figures) housed inside a
gearbox housing (not specifically shown in figures). The shifting fork is a metal
lever having a forked end. The shifting fork is configured to straddle a gear shaft
of the manual transmission gearbox. The function of the shifting fork is to slide at
least one gear in and out of engagement with other gears, in order to change the
transmission from one gear ratio to another in a manual transmission gearbox.
The gear shift lever 102 as shown in figure 3 is mechanically coupled with the
shifting fork (not specifically shown in figure) via the shifter rod 104. The gear
shift lever 102 is pivotally mounted on the shift lever housing 105, wherein the
shift lever housing 105 is provided in a driver's cabin and is easily accessible to
the driver. When the driver operates the gear shift lever 102, the motion of the
gear shift lever 102 is transferred to the shifter rod 104. The movement of the
shifter rod 104 results in the movement of the shifting fork, which ultimately
results in the change in the gear ratio of the transmission.
The device 150 comprises a plunger 152, a compression spring 154, a plunger
housing 156, a retainer 158, an opening 170 formed in a gear shift lever housing
105, and a control cable 172. The control cable 172 includes a wire 173 housed
inside a cable cover 171. The plunger 152 is free to reciprocate inside the plunger
housing 156. An anchor 173a portion is provided at one end of the wire 173
while the other end 173b of the cable wire 173 is connected to the clutch lever
120.
In accordance with an embodiment of the present disclosure, the opening 170 in
the shift lever housing 105 includes an annular base support 170a that surrounds
the plunger 152 and spring 154 along the axial space. The annular base support
170a is provided with first internal threads 170b as shown in figures. A first
operative end of the plunger 152 is provided with a protruding portion 152a while
the other end is configured to receive the anchor 173a of the wire 173. The
protruding portion 152a of the plunger 152 faces towards the shifter rod 104. The
plunger housing 156 having external threads near one end and internal threads
near the other end is fastened to the annular base support 170a of the opening 170
and defines a guiding path for the plunger 152 therein. The retainer 158 is
fastened to the internal threads of the plunger housing 156 after the plunger 152,
the spring 154, and anchor 173a is assembled in the plunger housing 156. The
plunger 152 is normally retained in an extended position (PI) due to the force
exerted by the compression spring 154 that is supported by the retainer 158. The
plunger 152 is retained in the extended position (PI) unless the driver presses the
clutch pedal. A first end 171a of the cable cover 171 is supported in the retainer
158, while the second end 171b is held by a support plate 175. The support plate
175 is fixedly mounted on the body or chassis of the vehicle.
At least one groove (104a, 104b... 104n) is formed in the shifter rod 104. The
grooves (104a, 104b... 104n) are further configured to receive the protruding
portion 152a of the plunger 152, when the plunger 152 is in the extended position
(PI).
In accordance with an embodiment of the present disclosure, the device 150 is
configured to abut the shifter rod 104 of the gearbox.
In accordance with another embodiment of the present disclosure, the device
opening 170 is configured to allow the passage of the shifter rod 104
therethrough.
The protruding portion 152a of the spring loaded plunger 152 is seated in at least
one of the grooves (104a, 104b.... 104n). The plunger 152 is linked to the control
cable 172 which is further configured to pull out the plunger 152 from the groove
(104a, 104b....104n). The retainer 158 maintains the plunger 152 seated in the
grooves (104a, 104b... 104n) by transmitting a compression force via the spring
154. The other end 173b of the wire 173 is connected to a clutch lever 120.
Whenever the clutch pedal is depressed, the clutch lever 120 pulls the other end
173b of the wire 173. The axial movement of the wire 173 pulls the protruding
portion 152a of the plunger 152 out of the groove (104a, 104b... 104n) and the
shifter rod 104 is free to move. As long as the clutch pedal is depressed, the
shifter rod 104 is free to move, and thus the gear shift lever 102 is permitted to be
operated by the driver. Upon removal of foot from the clutch pedal, the plunger
152 moves to its normally extended position and the protruding portion 152a of
the plunger 152 fits in any one of the grooves (104a, 104b... 104n), thus locking
the movement of the gear shift lever 102 and the shifter rod 104. Further, due to
the spring force the plunger 152 stays in extended position (PI) and locks the
movement of the gear shift lever 102 unless the clutch pedal is pressed.
The advantage of the device 150 is that it prevents the forceful operation of the
gear shift lever 102 while the vehicle's transmission clutch is still in the engaged
position and driven by the engine. This avoids the failure and damage of the
gearbox and drivetrain components.
The foregoing description of the embodiments has been provided for purposes of
illustration and not intended to limit the scope of the present disclosure.
Individual components of a particular embodiment are generally not limited to
that particular embodiment, but, are interchangeable. Such variations are not to be
regarded as a departure from the present disclosure, and all such modifications
are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages
including, but not limited to, the realization of a device for controlling the
operation of the gear shift lever, that:
• prevents the forceful operation of gear shift lever while the clutch is
engaged;
• reduces frequent breakdown of the gearbox;
• increases the life of the gearbox;
• is easy to maintain;
• is simple in construction;
• is easy to assemble;
• can be retrofitted on an existing gearbox; and
• is economical.
The foregoing description of the specific embodiments so fully reveals 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.
Throughout this specification the word "comprise", or variations such as
"comprises" or "comprising", will be understood to imply the inclusion of a
stated element, or group of elements, but not the exclusion of any other element,
or group of elements.
The use of the expression "at least" or "at least one" suggests the use of one or
more elements or ingredients or quantities, as the use may be in the embodiment
of the disclosure to achieve one or more of the desired objects or results.
Any discussion of materials, devices, articles or the like that has been included in
this specification is solely for the purpose of providing a context for the
disclosure. It is not to be taken as an admission that any or all of these matters
form a part of the prior art base or were common general knowledge in the field
relevant to the disclosure as it existed anywhere before the priority date of this
application.
While considerable emphasis has been placed herein on the components and
component parts of the preferred embodiments, it will be appreciated that many
embodiments can be made and that many changes can be made in the preferred
embodiments without departing from the principles of the disclosure. These and
other changes in the preferred embodiment as well as other embodiments of the
disclosure will be apparent to those skilled in the art from the disclosure herein,
whereby it is to be distinctly understood that the foregoing descriptive matter is to
be interpreted merely as illustrative of the disclosure and not as a limitation.

WE CLAIM:
1. A device (150) for enabling gear shifting operation only upon disengagement
of transmission clutch from the engine, said device (150) coupled to a manual
transmission gearbox, said gearbox comprising a shifter rod (104) connected
to said shift lever (102) through a pin, said device (150) comprising:
• a plunger housing (156) detachably fastened to shift lever housing
(105);
• a plurality of grooves (104a, 104b... 104n) formed on said shifter rod
(104), said grooves (104a, 104b... 104n) being configured to be in a
positive engagement with said plunger (152);
• a mechanically actuated spring loaded plunger (152) reciprocating
inside said plunger housing (156), said plunger (152) configured to be
normally in an extended position (PI), wherein in said extended
position (PI) said plunger (152) is in positive engagement with said
shifter rod (104) and thus the shifter rod (104) is prevented from
displacement; and
• a control cable (172) mechanically connecting said plunger (152) to a
clutch pedal, said control cable (172) configured to displace said
plunger (152) from said extended position (PI) to its retracted position
(P2) by the operation of said clutch pedal, wherein in said retracted
position (P2) of said plunger (152), said shifter rod (104) is free to
move.
2. The device (150) as claimed in claim 1, which includes a protruding portion
(152a) provided at a first operative end of said plunger (152), said protruding
portion (152a) configured to positively engage with at least one of said
grooves (104a, 104b... 104n) of said shifter rod (104).
3. The device (150) as claimed in claim 1, which includes a compression spring
(154) for retaining said plunger (152) in the extended position (PI).
4. The device (150) as claimed in claim 1, wherein said plunger housing (156) is
detachably fastened to a gear shift lever housing (105).
5. The device (150) as claimed in claim 1, wherein said plunger housing (156) is
detachably fastened to gearbox housing.