Background of the Invention
Field of the Invention
The present invention relates to a lock plate with a positive snap locking mechanism, without
incorporating any external spring back force principle used for locking any rotating object in clockwise or
counter clock wise or both directions in stationary housing and more particularly, it locks and guides the
magnet holder assembly in housing under external vibrations and also maintains constant air gap between
the magnet and hall Integrated Circuit, in dynamic and high operating temperature conditions.
Description of the Related Art
Conventional locking mechanism comprises of a lock ring, magnet holder and printed
circuit board assembly located in the housing. A magnet holder is engaged with D-shaft by
screw, the lock ring locks the magnet holder in the housing by a plurality of male snaps. There
are a plurality of tapered profile slots provided in the housing to lock the lock ring. The male
snap lock slides through the slots of the housing. The slots are provided with tapered profile to
ensure an interference fit between the male snap and female slots. Due to this interference fit, the
housing slots tend to expand in the axial direction, as the male snap slides in the slots. On further
rotation of the lock ring, the male snap gets locked in the grooves provided at the end of the
tapered profile slots in the housing due to Spring back force principle.
Due to thermal expansion of the housing in the axial direction, under high temperature
operating conditions, the snap lock tends to come out of the grooves and rotates in the reverse
direction of its locking, thus causing the lock ring to disassemble from the housing. As a result, it
fails in its primary function to hold and guide the magnet holder, in its original position. Under
vibrational environment, the lock ring may move out from locking groove provided at end of
3
tapered profile slot. Also, this type of locking mechanism does not work, where thin wall
thickness are designed in axial and radial direction due to space constraints, as thin wall breaks
in free fall tests. If this locking mechanism is used in a gear box mounted components, high
temperature oil comes in contact between male and female snap and reduce the coefficient of
friction between them, thus causing the lock ring to easily disengage from its locking position,
when an anti-locking force is applied by the rotating magnet holder.
Disadvantages of the Prior art
The Present invention overcomes one or more of prior art disadvantages. Firstly, in prior
art, the lock ring does not provide a positive locking with the housing. Secondly, the lock ring
can slide back out from its locked position in the reverse direction due to thermal expansion of
the housing under high temperature operating conditions. Thirdly, since the lock ring can
disassemble from the housing under external vibrations, due to this a constant air gap between
magnet and Hall Integrated Circuit is not maintained. Furthermore, this type of locking
mechanism does not work, where thin wall thickness are designed in the axial and radial
direction, due to space constraints as thin wall breaks in free fall tests. Also, high temperature oil
will come in between male and female snap and reduce coefficient of friction between them,
which causes the lock ring to easily disengage from its locking position when anti-locking force
is applied by rotating magnet holder. Finally, there is no reverse assembly POKA YOKE in lock
plate.
In the present invention, it avoids rotation of lock ring in the anti-locking direction. As
positive snaps restricts the movement of the magnet holder from its locking position under high
temperature, vibrations and magnet holder operating force conditions in reverse locking
4
direction. It also ensures reverse assembly POKA YOKE by the eccentric shape of the lock plate.
This lock plate maintains a constant air gap between Hall Integrated Circuit and Magnet in
dynamic conditions.
Objects of the Invention
Accordingly, it is a principal object of the present invention to overcome or ameliorate at
least one of the disadvantages of the prior art, or to provide a useful alternative.
Yet another object of this invention is to provide a lock plate with a positive snap lock
which has excellent mechanical strength and can be operated by a person of ordinary skill.
Additional advantages, objects, and features of the invention will be set forth in part in
the description which follows and in part will become apparent to those having ordinary skill in
the art upon examination of the following or may be learned from practice of the invention may
be realized and attained by the structure particularly pointed out in the written description hereof
as well as the appended drawings.
Summary of the Invention
Accordingly, the present invention is directed to a lock plate with positive snap lock,
which substantially obviates one or more problems due to limitations and disadvantages of the
related art.
A position sensor continuously captures angular position of rotating object for example, gear
shift drum by contactless Hall Technology. The said position sensor comprises a Hall mounted on printed
circuit board and magnet encapsulated in the magnet holder. As the magnet holder rotates according to shift
5
drum moment, the Integrated Circuit senses change in the magnetic field direction and gives analog voltage
output signal to the Electronic Control Unit.
The position sensor comprises of a unique locking mechanism inbuilt to guide and hold the
magnet holder in the housing under external vibrations and operating temperature conditions. It also
restricts the magnet holder movement in the axial direction. The Locking mechanism comprises of an
eccentric shaped lock plate with unique male snap lock. The snap lock is so designed, that it restricts the
lock plate from rotating in an anti-locking direction in dynamic conditions. The lock plate eccentric shape
ensures POKA YOKE, so that it should not be assembled in reverse direction in the housing. The lock plate
is locked in the housing by means of a flexible male snap locks as we rotate lock plate in the counter
clockwise direction. The male snap locks are deflected in downwards before entering in the guide pockets
provided in housing, as the lock plate is further rotated in CCW direction the male snap lock gets locked in
guide pockets by making positive lock with the housing.
When the magnet holder rotates against the locking direction of lock plate, the magnet holder
applies a torque to rotate lock plate along with it, However, during this condition the positive male snap
locks in the lock plate, thus restricting the rotation of the lock plate against the locking direction and
ensures robust and positive locking.
In present invention, design of the lock plate with positive snap locks along with
eccentric shape for accomplishing reverse assembly POKA-YOKE. Also the design maintains
constant air gap between magnet and hall Integrated Circuit in dynamic conditions are key
configurations.
Additional advantages, objects, and features of the invention will be set forth in part in
the description which follows and in part will become apparent to those having ordinary skill in
6
the art upon examination of the following or may be learned from practice of the invention may
be realized and attained by the structure particularly pointed out in the written description as well
as in the accompanying drawings.
Brief Description of the Accompanying Drawings
The invention will be described in conjunction with the accompanying drawings, in
which:
Figure 1 illustrates the prior art locking system;
Figure 2, illustrates the lock plate with positive snap locking according to an embodiment
of the present invention;
Figure 3 illustrates the lock plate according to an embodiment of the present invention;
Figure 4 illustrates the different views of the lock plate and sectional view of housing
assembly, according to an embodiment of the present invention;
Figure 5 illustrates the legend of the lock plate, according to an embodiment of the
present invention;
Figure 6 illustrates the assembly sequence exploded view in accordance with an
embodiment of the present invention.
Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity
and have not necessarily been drawn to scale. For example, the dimensions of some of the
elements in the drawings may be exaggerated relative to other elements to help to improve
understanding of embodiment of the present invention.
7
Detailed Description of Invention
While the invention is susceptible to various modifications and alternative forms, specific
embodiment thereof has been shown by way of example in the drawings and will be described in
detail below. It should be understood, however that it is not intended to limit the invention to the
particular forms disclosed, but on the contrary, the invention is to cover all modifications,
equivalents, and alternative falling within the spirit and the scope of the invention, as defined by
the appended claims.
Accordingly, the drawings are showing only those specific details that are pertinent to
understanding the embodiments of the present invention, so as not to obscure the disclosure with
details that will be readily apparent to those of ordinary skill in the art having benefit of the
description herein.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to
cover a non-exclusive inclusion, such that a setup, device that comprises a list of components
does not include only those components, but may include other components, not expressly listed
or inherent to such setup or device. In other words, one or more elements in a system or
apparatus proceeded by “comprises… a” does not, without more constraints, preclude the
existence of other elements or additional elements in the apparatus. The following paragraphs
explain present invention with respect to a lock plate with a positive snap locking mechanism.
The invention in respect of the same may be deduced accordingly.
Accordingly, the present invention provides a lock plate with a positive snap locking
mechanism, comprising: a position sensor for capturing the angular position of a rotating object
comprising a Printed circuit board assembly and a magnet holder assembly; said printed circuit
board assembly having a Hall Integrated circuit and electronic components and being located in
8
the housing; said magnet holder assembly comprising a magnet, magnet holder and D-shaft rotor
and screw; said magnet holder being located in the housing; a lock plate being placed on the said
magnet holder and rotated in counter clockwise direction until the male snap lock of the said lock
plate gets locked positively in the guide pockets; a D-shaft being coupled with a mating rotating
part on the vehicle; wherein the shift drum rotates in clockwise and / or counter clockwise
direction, and the D-shaft rotor rotates along with the shift drum.
According to another aspect of the present invention, the magnet holder is coupled to say
D-shaft rotor and it also rotates in both directions along with the said D-shaft.
According to another aspect of the present invention, the said lock plate avoids the
magnet holder coming out of said housing in axial direction during rotation.
According to another aspect of the present invention, the said lock plate has male snap
locks which are firmly locked in the housing slots.
According to another aspect of the present invention, the said male snap lock restricts the
said lock plate to rotate along with the magnet holder in dynamic conditions in the reverse
direction.
According to another aspect of the present invention, a constant air gap is maintained
between the said magnet and the said Hall Integrated circuit under external vibrations as the
magnet holder is locked in position by the lock plate, ensuring desired hall integrated circuit
output characteristics.
Referring now to the drawings, there is shown an illustrative embodiment of the lock plate
with a positive snap. It should be understood that the invention is susceptible to various
9
modifications and alternative forms; specific embodiment thereof has been shown by way of
example in the drawings and will be described in detail below.
Fig. 1 shows the prior art lock plate comprising of a lock ring, magnet holder (5) and
printed circuit board assembly (3) located in the housing (6). A magnet holder (5) is engaged
with D-shaft (8) by screw (7), the lock ring locks the magnet holder (5) in the housing (6) by a
plurality of male snaps (20). There are a plurality of tapered profile slots provided in housing (6)
to lock the lock ring (1). The male snap (20) slides through the slots of the housing, the slots are
provided with tapered profile to ensure an interference fit between male snap (20) and female
slots, due to this interference fit the housing slots tend to expand in axial direction, as the male
snap slides in the slots. On further rotation of the lock ring the male snap locks in the grooves
provided at the end of the tapered profile slots in housing due to Spring back force principle.
Referring to Figure 2 a position sensor is illustrated, which continuously captures angular
position of rotating object for example gear shift drum by contactless Hall Technology. It consists of Hall
(4) mounted on printed circuit board (3) and magnet (2) encapsulated in the magnet holder (5). As the
magnet holder (5) rotates according to shift drum moment, the Integrated Circuit (4) senses change in the
magnetic field direction and gives analog voltage output signal to the Electronic Control Unit.
The position sensor comprises of a unique locking mechanism inbuilt to guide and hold the
magnet holder (5) in the housing (6) under external vibrations and operating temperature conditions. It also
restricts the magnet holder (5) movement in the axial direction. The Locking mechanism comprises of an
eccentric shaped lock plate (1) with unique male snap lock (9). The snap lock is so designed, that it restricts
the lock plate (1) from rotating in an anti-locking direction in dynamic conditions. The lock plate (1)
eccentric shape ensures POKA YOKE, so that it should not be assembled in reverse direction in the
10
housing. The lock plate is locked in the housing (6) by means of a flexible male snap locks (9) as we rotate
lock plate (1) in the counter clockwise direction. The male snap locks are deflected in downwards before
entering in the guide pockets provided in housing (6), as the lock plate (1) is further rotated in CCW
direction the male snap lock gets locked in guide pockets (10) by making positive lock with the housing
(6).
When the magnet holder (5) rotates against the locking direction of lock plate (1), the magnet
holder (5) applies a torque to rotate lock plate (1) along with it, However during this condition the positive
male snap locks in the lock plate (1), thus restricting the rotation of the lock plate (1) against the locking
direction and ensures robust and positive locking.
The Position sensor comprises of a Printed Circuit Board assembly (3) and Magnet
holder assembly (5). The Printed Circuit Board assembly (3) comprises of Hall Integrated Circuit (4)
and electronic components. The Printed Circuit Board assembly (3) is located in the housing (6) by
pip and epoxy filling is done in the housing for protection of Printed Circuit Board assembly (3)
against entry of water and dust. The magnet holder assembly (5) comprises of magnet (2), magnet
holder (5), D-shaft rotor (8) and a screw (7). The magnet holder (5) along with the magnet (2) is first
located in the housing (6) then the lock plate (1) is placed on the magnet holder (5) and rotated in
counter clockwise direction, until the male snap lock (9) of the lock plate gets locked positively, in
the guide pockets (10), later the D-shaft (8) is engaged with the magnet holder by a self-tapping
screw (7). As the D-shaft (8) is coupled with mating rotating part on the motorcycle, like rotating
part, say shift drum rotates in clockwise and counter clockwise direction the D-shaft rotor rotates
along with shift drum. The magnet holder is coupled to D-shaft and it also rotates in both directions
along with the D-shaft. The lock plate (1) avoids the magnet holder (5) coming out of the housing
(6) in axial direction during rotation. This lock plate (1) has male snap locks which are firmly locked
11
in the housing guide pocket slots (10). The male snap lock also restricts the lock plate (1) to rotate
along with the magnet holder (5) in dynamic conditions in the reverse direction. As the magnet
holder (5) is locked in position by the lock plate (1), a constant air gap is maintained between the
magnet (2) and the Hall Integrated Circuit (4) under external vibrations, also ensuring hall Integrated
Circuit output characteristics as desired.
Advantages of the present invention over the Prior art
The main advantages of the present invention over the prior art is the positive locking of
the housing with the lock plate. Due to positive snap locks, the lock plate is restricted to rotate in
reverse locking direction under high temperature environments and dynamic conditions. The
lock plate guides and holds the magnet holder assembly in the required position which ensures
constant air gap between the Hall Integrated Circuit and magnet is maintained under external
vibrations. Hence, the sensor output characteristics will remain constant as desired. The Thin
wall thickness in the housing is avoided by unique snap lock design. Furthermore, this new
unique design is robust against free fall test. Also, the Lock plate does not fail in its primary
function to lock in housing under high temperature oil environment. The eccentric shape of lock
plate ensures reverse assembly of POKA YOKE.
The advantages of the disclosed invention are thus attained in an economical, practical,
and facile manner. While preferred aspects and example configurations have been shown and
described, it is to be understood that various further modifications and additional configurations
will be apparent to those skilled in the art. It is intended that the specific embodiments and
configurations herein disclosed are illustrative of the preferred nature and best mode of
12
practicing the invention, and should not be interpreted as limitations on the scope of the
invention.

WE CLAIM:
1. A lock plate with a positive snap locking mechanism, comprising:
a position sensor for capturing the angular position of a rotating object comprising a
Printed circuit board assembly and a magnet holder assembly; said printed circuit board
assembly having a Hall Integrated circuit and electronic components and being located in the
housing;
said magnet holder assembly comprising a magnet encapsulated in the magnet holder and
D-shaft rotor and screw; said magnet holder being located in the housing;
a lock plate being placed on the said magnet holder and rotated in counter clockwise
direction until the male snap lock of the said lock plate gets locked positively in the guide
pockets;
a D-shaft being coupled with a mating rotating part on the vehicle;
wherein the shift drum rotates in clockwise and / or counter clockwise direction, and the
D-shaft rotor rotates along with the shift drum.
2. The lock plate as claimed in claim 1, wherein the magnet holder is coupled to said Dshaft
and it also rotates in both directions along with the said D-shaft.
3. The lock plate as claimed in claim 1, wherein the said lock plate avoids the magnet
holder coming out of said housing in axial direction during rotation.
14
4. The lock plate as claimed in claim 3, wherein the said lock plate has male snap locks
which are firmly locked in the housing slots.
5. The lock plate as claimed in claim 4, wherein said male snap lock restricts the said lock
plate to rotate along with the magnet holder in dynamic conditions in the reverse direction.
6. The lock plate as claimed in claim 1, wherein a constant air gap is maintained between
the said magnet and the said Hall Integrated circuit under external vibrations as the magnet
holder is locked in position by the lock plate, ensuring desired hall integrated circuit output
characteristics.