FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF INVENTION
A Solenoid Operated Latching Device For Vehicles
APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Shivkumar H Chougule & Shekhar D Phulambrikar
Both Indian Nationals
of TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the
manner in which it is to be performed.

FIELD OF INVENTION
This invention relates to a latching device for vehicles and more particularly a latching device which can operate manually or electromechanically and adapted for use with vehicle fuel filler door latch system.
BACKGROUND OF INVENTION
In an effort to avoid unauthorized access to the vehicle fuel tank, fuel filler door as used with proper latching mechanism. This latching mechanism can be either manual or electromechanically operated from inside the vehicle. Conventionally latching system includes a striker bar fixed to the fuel filler door and a latch member engages the striker bar in a latched position when filler door is closed. To release the filler door the latch member is moved to unlatched position to disengage the striker bar, thereby allowing the fuel cap filler door to open freely for access to fuel cap. For convenience remotely activated fuel filler door release systems are used. Remotely actuated latching systems permit an occupant within the passenger compartment of the vehicle to open the fuel filler door prior to exiting the vehicle. Typically, remotely actuated latching systems include the use of a linear actuation cable or linkage coupled to the latch member for manually releasing the filler door. Alternatively an electrically actuated release systems are used to open the filler door. These systems typically include an electromechanical solenoid device mounted latch wherein the solenoid armature or plunger is acting as a latch member. Energization of the solenoid moves the armature ( plunger) to disengage the striker bar. The solenoid is energized by giving electric supply through switch, which is located in the passenger compartment.
Conventionally, the armature (plunger) is made of steel to get a tractive pull required of the solenoid. The solenoid is located inside a plastic housing and the plunger is moving to and fro inside the housing. One of the common problems by using a steel plunger is that it will easily corrode and the rust material restrict the


easy to and fro movement of the plunger inside the housing. This will affect the efficient releasing of the striker bar thereby affect the opening and closing of the fuel filler door. To avoid problem causing due to the corrosion, the plunger is provided with electro-less nickel plating. But again the to and fro movement of the plunger inside the housing may remove the nickel coating this may lead to corrosion causing inefficient movement of the latch member inside the housing and working of the latching system. Because of the fuel filler door is a fit and finish component of an automobile, it must be precisely aligned during assembly. It is common for conventional fuel filler latching mechanisms to require adjustment of the alignment between the latch member and the striker bar following vehicle assembly to ensure that the release system will function properly. Again, to maintain the alignment dimensional tolerance is required for critical portion of the plunger which is located near the striking bar. This involves machining operations like Turning, Milling, Surface grinding & cylindrical grinding resulting in long machining process time. Again the electro-less nickel plating require very long process time. The long manufacturing time and plating makes the plunger expensive. Since the plunger is made in steel higher voltage (5.8 to 6.2 V) is required to produce enough magnetic attractive force due to higher weight of steel. Consequently to assure adequate and efficient release of the striker bar, it is necessary to provide a relatively expensive solenoid.
OBJECTS OF INVENTION
Main object of this invention is to provide a latching device comprising of a solenoid wherein plunger of said solenoid acting a latch member, which is adequate and efficient in latching and unlatching the striker bar.
Another object of this invention is to provide a latching device which can be manufactured in less process time and requiring less voltage for activation.


Yet another object of this invention is to provide a latching device which is cost effective.
SUMMARY OF INVENTION
According to this invention a solenoid operated latching device for vehicles comprising, a housing, a movable composite plunger located inside said housing, a return spring disposed between a flange of said plunger and a interior wall of said housing to keep the tip of said plunger engaged with a locking member at its first position, an electromagnetically inductive coil wound around other end of said plunger to pull the plunger to second position by energizing said coil thereby disengaged with said locking member, wherein said composite plunger is having a first and second portion, said first portion is engaged with second by a locking means to restrict axial and rotational movement between said first and second portions, said first portion is made of a non-metallic material and second portion made of steel.
In conventional plated steel plunger wherein the exposed end is striking against the striker bar and lead to removal of plating there by causing corrosion at the end portion and also corrosion of the striker bar and other attached components. This will further lead to restrict the movement of plunger inside the housing during operation. By replacing steel with plastic the disadvantages due to the corrosion is avoided.
In conventional plated steel plunger, due to the higher weight of the plunger higher tractive force is required and this required higher voltage to operate. Where as, in the present invention the certain portion of plunger has been converted into plastic thereby reducing the weight resulted into lower operating voltage. With this new arrangement the operating voltage is reduced to 4.8 - 5.6V.


In conventional plated steel plunger to maintain the alignment dimensional tolerance is required for critical portion of the plunger which located near the striking bar. This involves stage wise machining operations like Turning, Milling, Surface grinding & cylindrical grinding resulting in long machining process time. Again the electro-less nickel plating require very long process time. The long manufacturing time and plating makes the plunger very expensive. In the present invention the critical portion has been replaced with plastic molding where the dimensional accuracy is maintained thereby avoid complex machining. Further second portion made in steel does not require surface hardening. Hence electro-less nickel plating is not required. The manufacturing cycle time is drastically reduced by avoiding complex machining. With the present composite plunger the manufacturing time has been reduced to one third of the conventional steel plunger. By avoiding complex manufacturing processes the total cost of the composite plunger can be reduced to one third of the conventional steel plunger.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 shows the details of latching system
Figure 2 shows the details of plunger
Figure 3 shows the insert locking
Figure 4 shows the side view of the insert locking
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
Referring to the Figure 1 and 2, the latching system (1) according to the present invention includes a solenoid assembly (2) and a puller (7). The solenoid assembly


having housing (6) with central bore to accommodate plunger (3) and electromagnetically inductive coil (4) wind around end portion of said plunger to produce electromotive force. The plunger is having a flange (13) and a conical return spring (5) is arranged between the flange and a wall located inside the housing. The tip of the plunger is angled so that while the striker bar (not shown) hit the plunger tips it moves the plunger inside of the housing against the biasing force of the spring. As the striker bar moves on the plunger tip and on reaching the striker bar depression, the force acting on the plunger by the striker bar to move against the biasing force of the spring will be removed to cause the plunger to move out of the housing there by locking the striker bar. The striker bar is attached to the fuel filler door of the vehicle and the hinged end of the door is in a pre tensioned mode so that once the plunger is moved inside housing the striker bar will unlock to move the filler door outward. To move the plunger inside of the housing either needs to activate the coil (4) or pull the plunger using a puller (7). By activating the coil an electromotive force is generated thereby move the plunger (3) inside the housing (6) against the biasing force of the return spring. The coil is activated or the solenoid is operated using any conventional electrical circuit where the controlling switch is located inside the passenger cabin. Incase if the electrical circuit is not working the plunger can be pulled mechanically by a puller (7) where the puller is located inside the passenger compartment.
To avoid the disadvantages of conventional plunger, it has been replaced with a composite plunger wherein critical portion where complex machining is required has been replaced with plastic molding and certain of portion of the plunger has been retained in steel to get a tractive pull required of the solenoid. Referring to figure 2, plunger is having two separate portions, a first (11) and second (10) portions. The first portion is made of plastic and the second portion is made of steel where the first and second portions are combined by insert molding process. Further the plastic is a poly phenyl sulphide. The bonding between the first and second portion is ensured by providing a locking arrangement (12). Referring to the figure 3 & 4, the locking arrangement (12) is made by providing an axial extension on the


second portion and further making peripheral groove (14) and a semi circular flat (13) at the end of it. The groove will restrict the separation due to the pulling force and the semi circular flat end will restrict the radial separation due to rotational forces. During the molding process the plastic will deposit in the grooves on the axial extension of the second portion thereby by make a perfect bond between the first and second portions.
By considering dimensional accuracies like concentricity, linearity and the steel portion required for generating tractive force, ratio of the plastic portion of the composite plunger has been chosen between 35 - 45% of the total length of the plunger or preferably 42% of the total length of the plunger.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.


WE CLAIM
1. A solenoid operated latching device for vehicles comprising, a housing, a movable composite plunger located inside said housing, a return spring disposed between a flange of said plunger and a interior wall of said housing to keep the tip of said plunger engaged with a locking member at its first position, an electromagnetically inductive coil wound around other end of said plunger to pull the plunger to second position by energizing said coil thereby disengaged with said locking member, wherein said composite plunger is having a first and second portion, said first portion is engaged with second by a locking means to restrict axial and rotational movement between said first and second portions, said first portion is made of a non-metallic material and second portion made of steel.
2. The solenoid operated latching device for vehicles as claimed in claim 1 wherein said locking means is formed by an axial extension of said second portion having peripheral grooves and semi circular flat at end, insert molded with the first portion of said plunger.
3. The solenoid operated latching device for vehicles as claimed in claim 1 wherein said non-metallic material is poly phenyl sulphide.
4. The solenoid operated latching device for vehicles as claimed in claim 1 wherein ratio between length of said first portion and length of said plunger is in the range of 0.35 to 0.45
5. The solenoid operated latching device for vehicles as claimed in claim 4 wherein ratio between length of said first portion and length of said plunger is 0.42.


6. The solenoid operated latching device for vehicles as claimed in claim 1 wherein one end of said plunger opposite to said tip member is mechanically connected to a puller to pull the plunger to disengage with said locking member.
7. The solenoid operated latching device for vehicles substantially as herein described with reference to accompanying drawings.
Dated this 19th day of February 2008





ABSTRACT
A Solenoid Operated Latching Device For Vehicles
Figure 1
This invention relates to a latching device comprising of a solenoid wherein plunger of said solenoid acting a latch member, which is adequate and efficient in latching and unlatching the striker bar, can be manufactured in less process time and requiring less voltage for activation and is cost effective. According to this invention solenoid with a composite plunger wherein said plunger is having two separate portions made in non-metallic and in steel thereby avoiding critical manufacturing processes required incase of steel plunger and also avoiding corrosion. These two separate portions are combined using a locking means formed by insert molding to restrict the axial and rotational movement. By avoiding critical machining the manufacturing time and cost can be reduced.