FORM 2
THE PATENTS ACT 1970
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
"A wiper drive mechanism"
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
Mr. Anand R Kale & Mr. Onkar D Gorade an Indian national
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 describes the invention and the manner in which it is
performed.

FIELD OF INVENTION
The present invention generally relates to windshield wiper arm for automobiles and more particularly to a windshield wiper with a screw joint in wiper spindle to reduce force on windshield curved glass.
BACKGROUND OF INVENTION
Windshield wiping mechanism is generally used in vehicles to wipe the windshield glass to make it free from water, dirt and dust. The windshield wiper drive mechanisms generally comprise a motor connected to a reciprocating mechanism which converts the rotary motion of the motor into a reciprocating motion required for output shaft. The output shaft may include a spindle of a wiper arm, or it may drive the wiper arm or arms via a suitable linkage. The conventional wiper mechanisms include a motor driven spindle with a cylindrical joint, wiper arm and a blade. Due to significant cross curvature on glass the forces on wiper blade are high and hence spring stiffness required is also high. During forwards and reverse movement of the output shaft of wiper arm, the force on the wiper blade limits its reciprocating movement causing rapid wear and even failure of the wiper arm. The friction between the wiper blades and windshield is accounted for in the bearing friction component. Hence there is need for a mechanism to reduce the force of wiper blade on glass and to increase the durability of blade rubber. To resolve these drawbacks stated above a windscreen wiper mechanism has been develop which reduces the force exerted by wiper blade on the glass and increases the durability of blade rubber. The life of the wiper blade is increased by reducing the force on windscreen glass and the chattering of wiper blade is reduced.

OBJECT OF THE INVENTION
The main object of this invention is to reduce the forces of the wiper blade on glass and to increase the durability of blade rubber.
SUMMARY OF THE INVENTION
The present invention relates to a windscreen wiper assembly for a motor vehicle comprises a wiper blade provided on a free end of a wiper arm, said wiper blade is placed on a windscreen of said motor vehicle, a motor for generating driving force for said wiper arm, a wiper link drivingly connected to said motor for executing rotary motion, a linkage operatively connected to said wiper link for transforming the rotary motion of said wiper link into reciprocating motion, and a wiper spindle for transforming said reciprocating motion of said linkage into torsional oscillatory motion, said wiper spindle being operatively connected to said linkage and said wiper arm, wherein said wiper spindle is configured to move along its axis of torsional oscillation while executing said torsional oscillatory motion wiper arm is driven by the output of said wiper spindle and is adapted to execute to and fro motion about said wiper spindle along the surface of said windscreen in such a way that during movement, the wiper blade is raised or lowered across the plane of its movement to match the curvature of the windscreen, the raising and lowering of the wiper blade being preselectedly controlled by the spindle pitch.
According to the preferred embodiment of the invention, said assembly is provided with a wiper housing within which said wiper spindle executes torsional oscillatory motion, said wiper housing is held in position by means of a protruding arm extending from said motor.

According to the particular embodiment of the invention, said wiper spindle is externally threaded and said wiper housing is internally threaded, the external thread on said wiper spindle is adapted to match with the internals threads of said wiper housing.
Most preferably, said wiper spindle moves up and down in reciprocating manner within said wiper housing to move the wiper blade in forward and reverse direction to clean the windscreen glass. When the wiper spindle in said wiper housing reciprocates in upward direction the wiper blade moves in forward direction and when the wiper spindle in said wiper housing reciprocates in downward direction the wiper blade moves in reverse direction.
Preferably, said wiper spindle has its top end connected to the wiper arm and its bottom end connected to said linkage.
Preferably, said linkage has its one end connected to the wiper link and its other end connected to said wiper spindle.
According to the preferred embodiment of the invention, said ends of said linkage are coupled to wiper link and wiper spindle respectively by a ball joint.
Preferably, said motor drives the wiper link in 360 degree to produce rotary motion of said wiper link.
BRIEF DESCRIPTION OF INVENTION
The various embodiments of the present invention provide a windscreen wiper arm with a screw joint in wiper spindle. The mechanism comprises wiper spindle

housing with internal threads. A wiper spindle having external threads is secured in said wiper spindle housing. The top end of said wiper spindle is coupled with a fixed part of motor mounting bracket in a wiper arm by threaded joint. The bottom end of said wiper spindle is coupled to ball joint in connecting link. A spindle washer and a spindle ring are inserted while coupling said top end of said wiper spindle with wiper arm. The other end of the wiper arm with a wiper blade is positioned on a windscreen. When the wiper motor is operated the wiper motor drives the wiper link in 360° degree to oscillate wiper link.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an exploded view of a wiper arm with a screw joint, according to present invention.
FIG. 2 shows an assembly of wiper arm with a screw joint in wiper spindle, according to present invention.
FIG. 3 shows assembling of wiper arm with windscreen glass, according to present invention.
Description of reference numbers for the major component of the present invention in the drawings:
1- Wiper arm
2- Spindle ring
3- Spindle washer
4- Wiper housing
5- Wiper spindle
5a- Top end of wiper spindle

5b- Bottom end of wiper spindle
6- Connecting link
6a- one end of connecting link (6) 6b- Another end of connecting link (6)
7- Wiper motor
8- Wiper link
9- Wiper blade 10-Protruding arm
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the accompanying 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.
The various embodiments of the present invention provide a windscreen wiper arm with a screw joint in wiper spindle. The mechanism comprises a wiper spindle housing (4) with internal threads. A wiper spindle (5) having external threads are secured in said wiper spindle housing (4). The top end (5a) of said wiper spindle (5) is coupled with a fixed part of motor mounting bracket in a wiper arm by threaded joint. The bottom end (5b) of said wiper spindle (5) is coupled to ball joint of a connecting link (6). The connecting link (6) has its one end (6a) connected to a wiper link (8) and its other end (6b) connected to the wiper spindle (5). The ends (6a, 6b) of the connecting link are coupled to wiper link (8) and wiper spindle (5) by a ball joint. A spindle washer (3) and a spindle ring (2) are inserted while coupling said top end (5a) of said wiper spindle (5) with wiper arm (1). The free end of the wiper arm (1) is provided with a wiper blade which is positioned on a

windscreen. When the wiper motor (7) is operated the wiper motor drives the wiper link (8) in 360° degree to oscillate wiper link.
The oscillation motion from wiper motor (7) is transferred to the wiper blade through wiper motor link (8), connecting link (6), wiper spindle (5) and wiper arm (1). The wiper spindle (5) moves up and down in the wiper housing (4) to move the wiper blade in forward and reverse direction to clean the windscreen glass. As the wiper spindle reciprocates in the wiper spindle housing, it reduces the force on windscreen glass during the wiping condition. When the wiper blade moves in forwards direction the wiper spindle in said spindle housing reciprocates in upward direction to reduce the force on the windscreen. Similarly, when the wiper blade moves in reverse direction the wiper spindle in said spindle housing reciprocates in downward direction to reduce the force on the windscreen. The reduction of force on the windscreen depends on the pitch of the wiper spindle. The pitch of the wiper spindle depend on the following factors curvature of glass, wiping area, number of cycle required in high and low speed as per Automotive Industry Standards (AIS) 019 standard.
During operation, the motors drives the motor linkages with 360degree rotation, from which linkages converts it to the desired angle to the spindle which is rotating and fixed with main arm. The main arm on which the blade is fixed wipes the windscreen surface. The surface has curvature where the blade construction of leaf spring is used and in the main arm the coil spring is used, the screw joint in spindle gives the up/down to the blade which relaxes the spring tensions.
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 windscreen wiper assembly for a motor vehicle comprising:
- a wiper blade (9) provided on a free end of a wiper arm (1), said wiper blade (9) is placed on a windscreen of said motor vehicle,
- a motor (7) for generating driving force for said wiper arm (1),
- a wiper link (8) drivingly connected to said motor (7) for executing rotary motion,
- a linkage (6) operatively connected to said wiper link (8) for transforming the rotary motion of said wiper link (8) into reciprocating motion, and
- a wiper spindle (5) for transforming said reciprocating motion of said linkage into torsional oscillatory motion, said wiper spindle (5) being operatively connected to said linkage (6) and said wiper arm (9),
wherein said wiper spindle is configured to move along its axis of torsional oscillation while executing said torsional oscillatory motion and said wiper arm is driven by the output of said wiper spindle and is adapted to execute to and fro motion about said wiper spindle along the surface of said windscreen in such a way that during movement, the wiper blade is raised or lowered across the plane of its movement to match the curvature of the windscreen, the raising and lowering of the wiper blade being preselectedly controlled by the spindle pitch.
2. The windscreen wiper assembly as claimed in claim 1, wherein said assembly is
provided with a wiper housing (4) within which said wiper spindle (5) executes
torsional oscillatory motion, said wiper housing (4) is held in position by means
of a protruding arm (10) extending from said motor (7).

3. The windscreen wiper assembly as claimed in claim 2, wherein said wiper spindle (5) is externally threaded and said wiper housing (4) is internally threaded, the external thread on said wiper spindle (5) is adapted to match with the internals threads of said wiper housing (4).
4. The windscreen wiper assembly as claimed in claims 1 to 3, wherein said wiper spindle (5) moves up and down in reciprocating manner within said wiper housing (4) to move the wiper blade (9) in forward and reverse direction to clean the windscreen glass.
5. The windscreen wiper assembly as claimed in claims 1 to 4, wherein when the wiper spindle (5) in said wiper housing (4) reciprocates in upward direction the wiper blade (9) moves in forward direction and when the wiper spindle (5) in said wiper housing (4) reciprocates in downward direction the wiper blade (9) moves in reverse direction.
6. The windscreen wiper assembly as claimed in claims 1to 5, wherein said wiper spindle (5) has its top end (5a) connected to said wiper arm (1) and its bottom end (5b) connected to said linkage (6).
7. The windscreen wiper assembly as claimed in claims lto 6, wherein said linkage (6) has its one end (6a) connected to said wiper link (8) and its other end (6b) connected to said wiper spindle (5).
8. The windscreen wiper assembly as claimed in claims lto 7, wherein said ends (6a, 6b) of said linkage (6) are coupled to wiper link (8) and wiper spindle (5) respectively by a ball joint.

9. The windscreen wiper assembly as claimed in claims lto 8, wherein said motor (7) drives the wiper link (8) in 360 degree to produce rotary motion of said wiper link (8).