FIELD OF INVENTION:
[001] The present subject matter described herein, relates to a shift fork structure
of manual transmission in a vehicle, and, in particular, to an adjustable two piece
fork for manual transmission. The present uniform adjustable 5 shift fork can be
used for all pair of gears in the gear shift system instead of different configuration
shift forks.
BACKGROUND AND PRIOR ART:
[002] Generally, a shift fork is used to switch gears in a vehicle transmission in
10 gear box. The shift forks are employed in vehicular transmissions to translate the
means employed therein to select the desired gear ratio between the engine and
the drive wheels of the vehicle. The shift forks receives input load from the shift
shaft and moves the sleeve over gears for engagement. Generally, the shift fork is
formed as a single piece structure. Further, the structure and use of the shift fork is
15 well known in the art.
[003] Fig. 1 and 2 illustrate structure and use of the shift fork in the vehicle
transmission. The gear shift system 100 comprises a lever Gear Shift and select
(LGSS) 1, yokes 2, shifting shafts 3, forks 4, sleeves 5, and reverse gear lever 6.
In the six gear vehicle, there are three shifting shafts 3 for gear pair 1st - 2nd, gear
20 pair 3rd – 4th and gear pair 5th and reverse gear. Similarly, there are three shift
forks 4 for gear pair 1st - 2nd, gear pair 3rd – 4th and gear pair 5th and reverse gear.
Similarly, there are three yokes 2 which are attached to the shifting shaft 3 and
forks 4 for engaging the various gear pairs. The size of sleeves 5 for each pair of
gear vary due to which size of the shift fork 4 varies. Accordingly, there are three
25 shift forks for the 1-2 gear, 3-4 gear and 5-reverse gear, the three shift forks are
mounted on respective shift rails. As per present design of the gear shift system,
100, three different sizes of shift forks 4 are required in the six gear shift system.
[004] As shown in the figure 1, during the gear shifting, LGSS 1 moves the yoke
2 attached to shifting shafts 3 which in turn moves the shifting shafts 3. The
3
movement of shifting shafts 3 causes the movement of forks 4 which are attached
to shifting shafts only which in turn moves the sleeves 5 to engage various gears.
The reverse gear also gets actuated by movement of reverse gear lever 6 attached
to shifting shaft 3.
[005] Figure 2 shows the single shift shaft 3 and single sleeve and 5 shift fork. The
figure illustrates one of the shaft system along with fork and yoke arrangement.
As shown in the figure, the fork 4 is a single body and is attached to the shifting
shaft 3 with the help of welding. The shift fork 4 has different shaper and size for
different gear/sleeve arrangement. Accordingly, a plurality of different forks is
10 required for gear shift system.
[006] Technical problem associated with the shift fork is that different design
and development is required for different synchro packs resulting in cost increase.
[007] Therefore, there is a need in the art to manufacture a universal shift fork
which can be used for any gear and sleeve pair. The present invention has been
15 conceived in view of the aforementioned circumstances.
OBJECTS OF THE INVENTION:
[008] The principal objective of the present invention is to provide a universal
adjustable shift fork.
[009] Another object of the present invention is to provide an adjustable shift
20 fork which can be resized to a plurality of shift fork sizes.
[0010] Another object of the present invention is to provide an adjustable shift
fork with two fork arms where one fork arm is assembled on the other fork arm
via pin/rivet.
[0011] Yet another object of the present invention is to provide a simple,
25 effective, and cost efficient adjustable shift fork for equal stiffness and absorption
of vibrations.
4
SUMMARY OF THE INVENTION:
[0012] The subject matter disclosed herein relates to an adjustable shift fork for
manual transmission. The present adjustable shift fork has two arms. The
adjustable shift fork comprises a hub portion connected with a shift shaft. Further,
the adjustable shift fork has a first fork arm radially extending 5 from the hub
portion adapted to engage with circumference of sleeve and other fork arm
extending radially opposite to the first fork arm from the hub portion. The other
fork arm has a rivet hole and at least three locking hole for fixing second
adjustable fork arm. The second adjustable fork arm assembled on the other fork
10 arm. The second adjustable fork arm has a locking hole and a rivet. Further, the
second adjustable fork arm and the other fork arm are assembled by the rivet joint
and the locking holes. A rivet passes through the rivet hole of the other fork arm
and the rivet hole of the second adjustable fork arm to rotatably mount the
adjustable second fork arm with the other fork arm which extends from the hub
15 portion. For adjusting the different sizes of the shift fork, a locking pin engages
with the locking hole of the second adjustable fork arm and the at least one
locking hole of the other fork arm.
[0013] In order to further understand the characteristics and technical contents of
the present subject matter, a description relating thereto will be made with
20 reference to the accompanying drawings. However, the drawings are illustrative
only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] It is to be noted, however, that the appended drawings illustrate only
typical embodiments of the present subject matter and are therefore not to be
25 considered for limiting of its scope, for the invention may admit to other equally
effective embodiments. The detailed description is described with reference to the
accompanying figures. In the figures, the left-most digit(s) of a reference number
identifies the figure in which the reference number first appears. The same
numbers are used throughout the figures to reference like features and
30 components. Some embodiments of system or methods in accordance with
5
embodiments of the present subject matter are now described, by way of example,
and with reference to the accompanying figures, in which:
[0015] Fig. 1 illustrates gear shifting system in general;
[0016] Fig. 2 illustrates gear shifting system with single sleeve and single shifting
shaft as shown 5 in the fig. 1;
[0017] Fig. 3a illustrates gear shifting system with present adjustable shift fork, in
accordance with an embodiment of the present subject matter;
[0018] Fig. 3b illustrates structure of the adjustable shift fork arms, in accordance
with an embodiment of the present subject matter; and
10 [0019] Fig. 4 illustrates multiple size shift fork achieved by the adjustable shift
fork of figure 3b, in accordance with an embodiment of the present subject matter.
[0020] The figures depict embodiments of the present subject matter for the
purposes of illustration only. A person skilled in the art will easily recognize from
the following description that alternative embodiments of the structures and
15 methods illustrated herein may be employed without departing from the principles
of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0021] The subject matter disclosed herein relates to an adjustable shift fork for
manual transmission. The present adjustable shift fork has two arms. The
20 adjustable shift fork comprises a hub portion connected with a shift shaft. Further,
the adjustable shift fork has a first fork arm radially extending from the hub
portion adapted to engage with circumference of sleeve and other fork arm
extending radially opposite to the first fork arm from the hub portion. The other
fork arm has a rivet hole and at least three locking hole for fixing second
25 adjustable fork arm. The second adjustable fork arm assembled on the other fork
arm. The second adjustable fork arm has a locking hole and a rivet. Further, the
second adjustable fork arm and the other fork arm are assembled by the rivet joint
and the locking holes. A rivet passes through the rivet hole of the other fork arm
and the rivet hole of the second adjustable fork arm to rotatably mount the
6
adjustable second fork arm with the other fork arm which extends from the hub
portion. For adjusting the different sizes of the shift fork, a locking pin engages
with the locking hole of the second adjustable fork arm and the at least one
locking hole of the other fork arm.
[0022] It should be noted that the description and figures merely 5 illustrate the
principles of the present subject matter. It should be appreciated by those skilled
in the art that conception and specific embodiment disclosed may be readily
utilized as a basis for modifying or designing other structures for carrying out the
same purposes of the present subject matter. It should also be appreciated by those
10 skilled in the art that by devising various assembly that, although not explicitly
described or shown herein, embody the principles of the present subject matter
and are included within its scope. Furthermore, all examples recited herein are
principally intended expressly to be for pedagogical purposes to aid the reader in
understanding the principles of the present subject matter and the concepts
15 contributed by the inventor(s) to furthering the art, and are to be construed as
being without limitation to such specifically recited examples and conditions. The
novel features which are believed to be characteristic of the present subject matter,
both as to its organization and method of operation, together with further objects
and advantages will be better understood from the following description when
20 considered in connection with the accompanying figures.
[0023] These and other advantages of the present subject matter would be
described in greater detail with reference to the following figures. It should be
noted that the description merely illustrates the principles of the present subject
matter. It will thus be appreciated that those skilled in the art will be able to devise
25 various arrangements that, although not explicitly described herein, embody the
principles of the present subject matter and are included within its scope.
[0024] The shift forks are integral part of gear shift system in transmission. The
purpose of which is to engage the gears. In the present shift fork is made in two
parts instead of a single body. One part is attached to the shifting shaft through
30 welding and other part is joined to the first part with a help of a riveted joint.
7
[0025] In the present gear shifting system as shown in the figure 3a, the adjustable
shift fork 4 is made in two parts instead of conventional single body structure.
One part 4-a, is welded to shifting shaft 3 and other part 4-b is assembled to first
part 4-a through riveted joint 6.
[0026] Fig. 3b illustrates structure of adjustable shift fork 5 with fork arms, in
accordance with an embodiment of the present subject matter. The adjustable shift
fork 300 has a hub portion 301 which is connected with the shift shaft. The hub
portion 301 extends and bifurcates into two arms, such as first arm 301a and other
arm 302. The other arm 302 is smaller than the first arm 301a in circumference.
10 The first arm 301a extends in radially direction to define a circular path for
receiving circumference of the sleeve. The other fork arm 302 and the first fork
arm 301a are integrated with each other and act as a single arm. The other fork
arm 302 extending radially opposite to the first fork arm 301a from the hub
portion 301. The other fork arm 302 has a rivet hole 306a and at least three
15 locking hole 308a, 308b, 308c at distal end. The other fork arm 302 has step cut at
the distal end to receive opposite step cut end of a second adjustable fork arm
302a. The second adjustable fork arm 302a assembled on the other fork arm 302
at the end. The second adjustable fork arm 302a has step cut at the end which is
towards the other fork arm for assembly. Further, the step cut of the second
20 adjustable fork arm 302a is opposite to the other fork arm 302. The step cut on the
second adjustable fork arm 302a and the other fork arm 302 are provided for equal
surface assembly. The second adjustable fork arm 302a has a locking hole 307
and a rivet hole 306b.
[0027] In the assembly of the second adjustable fork arm 302a and the other fork
25 arm 302, a rivet 303 is provided for pivot joint of the second adjustable fork arm
302a and the other fork arm 302. The rivet 303 passes through the rivet hole 306a
of the other fork arm 302 and the rivet hole 306b of the second adjustable fork
arm 302a and makes a pivot joint between the second adjustable fork arm 302a
and the other fork arm 302. The rivet 303 joins the rivet hole 306a of the other
30 fork arm 302 and the rivet hole 306b of the second adjustable arm 302a.
8
[0028] Further, a locking pin 305 is provided to lock or fix the second adjustable
fork arm 302a and the other fork arm 302 with each other. The locking pin 305
engages with the locking hole 307 of the second adjustable fork arm 302a and the
at least one locking hole 308a, 308b, 308c of the other fork arm 302 to adjust
different sizes of the 5 shift fork 300.
[0029] In the 5 speed vehicles, there are three pairs of gears, i.e., gear pair 1st –
2nd, gear pair 3rd - 4th, and gear pair 5th and reverse gear. For easy of explanation,
the present subject matter is explained with reference to the six gear vehicles. The
present subject matter should not be limited to six gear vehicle, it can be
10 implemented on gear shift system which has N number of gears. For example, the
the locking pin 305 locks the locking hole 307 of the second adjustable fork arm
302a with the locking hole 308a from the at least one locking hole 308a, 308b,
308c to define the adjustable shift fork 300 for one gear pair. In another
arrangement, the locking pin 305 locks the locking hole 307 of the second
15 adjustable fork arm 302a with the locking hole 308b from the at least one locking
hole 308a, 308b, 308c to define the adjustable shift fork 300 for second gear pair.
In yet another arrangement, the locking pin 305 locks the locking hole 307 of the
second adjustable fork arm 302a with the locking hole 308c from the at least one
locking hole 308a, 308b, 308c to define the adjustable shift fork 300 for third gear
20 pair. The shift fork 300 has plastic shoes 310, 310a at both ends of the first fork
arm 301a and the second adjustable fork arm 302a to receive the sleeve. The first
fork arm 301a and the second adjustable fork arm 302a define a circular shape for
receiving the circular sleeve.
[001] Accordingly, the present shift fork 300 can be used as a common shift fork
25 for all gear combinations. As shown in the figure 4, the various shift fork sizes,
such as shift fork with fork arms 401+402, shift fork with fork arms 401+403, and
the shift fork with fork arms 401+ 404. Therefore, there is no need to have a
different shift fork sizes with different shape and configuration for each gear pair.
The present shift fork 300 act as a universal or common shift fork which can be
9
used at all gear pairs. So, a plurality of adjustable forks 300 can be used in the
gear shift system.
[002] The present adjustable shift fork is common part which can be used for all
the synchro packs due to usage of adjustable fork.
[003] The term “vehicle” as used throughout this detailed description 5 and in the
claims refers to any moving vehicle that is capable of carrying one or more human
occupants and is powered by any form of energy. The term “vehicle” is a motor
vehicle which includes, but is not limited to: cars, trucks, vans, minivans,
hatchback, sedan, MUVs, and SUVs.
10 [004] It will be further appreciated that functions or structures of a plurality of
components or steps may be combined into a single component or step, or the
functions or structures of one-step or component may be split among plural steps
or components. The present invention contemplates all of these combinations.
Unless stated otherwise, dimensions and geometries of the various structures
15 depicted herein are not intended to be restrictive of the invention, and other
dimensions or geometries are possible. In addition, while a feature of the present
invention may have been described in the context of only one of the illustrated
embodiments, such feature may be combined with one or more other features of
other embodiments, for any given application. It will also be appreciated from the
20 above that the fabrication of the unique structures herein and the operation thereof
also constitute methods in accordance with the present invention. The present
invention also encompasses intermediate and end products resulting from the
practice of the methods herein. The use of “comprising” or “including” also
contemplates embodiments that “consist essentially of” or “consist of” the recited
25 feature.
[005] Although embodiments for the present subject matter have been described
in language specific to structural features, it is to be understood that the present
subject matter is not necessarily limited to the specific features described. Rather,
the specific features and methods are disclosed as embodiments for the present
30 subject matter. Numerous modifications and adaptations of the system/component
10
of the present invention will be apparent to those skilled in the art, and thus it is
intended by the appended claims to cover all such modifications and adaptations
which fall within the scope of the present subject matter.

We claim:
1. A shift fork (300) for transmission in a vehicle, the shift fork (300)
comprising:
a hub portion (301) connected with a shift shaft (3);
a first fork arm (301a) radially extending from the 5 hub portion (301)
adapted to engage with circumference of sleeve (5);
a other fork arm (302) extending radially opposite to the first fork arm
(301a) from the hub portion (301), wherein the other fork arm (302) has a
rivet hole (306a) and at least three locking hole (308a, 308b, 308c); and
10 a second adjustable fork arm (302a) assembled on the other fork arm
(302) of the hub portion (301), wherein the second adjustable fork arm (302)
has a locking hole (307) and a rivet hole (306b), wherein assembly of the
second adjustable fork arm (302a) and the other fork arm (302) comprising:
a rivet (303) which joins the rivet hole (306a) of the other fork arm
15 (302) and the rivet hole (306b) of the second adjustable arm (302a); and
a locking pin (305) which engages with the locking hole (307) of the
second adjustable fork arm (302a) and the at least one locking hole (308a,
308b, 308c) of the other fork arm (302) to adjust different sizes of the shift
fork (300).
20
2. The shift fork (300) as claimed in claim 1, wherein the locking pin (305)
locks the locking hole (307) of the second adjustable fork arm (302a) with
the locking hole (308a) from the at least one locking hole (308a, 308b,
308c) to define the shift fork (300) for one gear pair.
25
3. The shift fork (300) as claimed in claim 1, wherein the locking pin (305)
locks the locking hole (307) of the second adjustable fork arm (302a) with
the locking hole (308b) from the at least one locking hole (308a, 308b,
308c) to define the shift fork (300) for second gear pair.
30
12
4. The shift fork (300) as claimed in claim 1, wherein the locking pin (305)
locks the locking hole (307) of the second adjustable fork arm (302a) with
the locking hole (308c) from the at least one locking hole (308a, 308b,
308c) to define the shift fork (300) for third gear pair.
5
5. The shift fork (300) as claimed in claim 1, wherein the other fork arm (302)
is integrated with the hub (301) and the first fork arm (301a).
6. The shift fork (300) as claimed in claim 1, wherein the shift fork (300) is
10 common shift fork for all gear combinations.
7. The shift fork (300) as claimed in claim 1, wherein the shift fork (300) is an
adjustable fork.
15 8. The shift fork (300) as claimed in claim 1, wherein the shift fork (300) has
plastic shoes (310, 310a) at both ends of the first fork arm (301a) and the
second adjustable fork arm (302a).