FORM 2
THE PATENTS ACT 1970
As amended by the Patents (Amendment) Aot 1999
COMPLETE SPECIFICATION
SECTION 10
TITLE
A device for vibrating and accurately locating electrical contacts on base terminals in brazing

APPLICANTS
Larsen & Toubro Limited, an Indian company having its registered office at L & T House, Ballard Estate, Mumbai 400001, Maharashtra, India
INVENTORS
Under Section 28(2)
Susheel Narayan Choubal, Larsen & Tourbo Limited, Near Custom House, Versova Creek, Madh, Mumbai -400081, Maharashtra, India, and Sanjay Dattatraya Vartak, Larsen & Toubro Limited, Powai Works, Saki Vihar Road, Mumbai - 400072, Maharashtra, India, both Indian citizens
The following specification particularly describes and ascertains the nature of this -invention and the manner in which it is to he performed :


This invention relates to a device for vibrating and accurately locating electrical contacts on base terminals in brazing.
PRIOR ART
In electrical industry, contacts are bonded to base terminals by brazing using a fusing material foil or wire interposed therebetween at a gap of about 0.1mm. The melting point of the fusing material foil or wire is lower than that of the parent metals with which the contacts and terminals are made. Therefore, during brazing the parent metals do not melt. Instead the foil or wire melts, flows through the gap between the parent metals by capillary action and forms a metallurgical bond between the parent metals. Typically silver-cadmium oxide is used for contacts, copper or brass is used for terminals and silver and copper alloy is used for foil or wire. A commonly used arrangement for brazing comprises a fixture provided with locator and heat source such as oxy-acetylene gas or liqufied petroleum gas or induction heating or resistance heating. A base terminal is supported on the fixture followed by placing the foil or wire on the terminal and the contact on the foil or wire.

In manual brazing, while the heat source is on, air entrapped between the contact and terminal ie air pockets is removed by wiping (moving to and fro) the contact on the terminal followed by locating the contact against the locator by an operator using a pincer. The heat source is removed or switched off after location of the contact against the locator. The molten foil or wire solidifies and bonds the contact to the terminal. In manual brazing it is possible to locate the contact against the locator accurately, which is critical for functional efficiency of the contact assembly. Manual brazing is, however, troublesome and inconvenient to carry out and requires the services of a very skilled operator. Still there are chances of mislocation of the contact against the locator due to human errors resulting from instances such as operator fatigue or wrong judgement or observation. Manual brazing does not remove entrapped air bubbles effectively. Therefore, the bond between the contact and terminal is not very good and strong.
In mechanical brazing, a vibrator rod comprising a bent tip engages against the contact and vibrates it to and fro horizontally in the

direction of the locator to wipe and remove the entrapped air bubbles between the contact and terminal. Due to mechanical vibration in mechanical brazing removal of entrapped air bubbles is very effective thereby improving the bond and bond strength between the contact and terminal. It is easy and convenient to carryout and does not require the services of a very skilled operator. In mechanical brazing, the contact is, however, left on the terminal at the location at which the vibrator stopped vibrating. Because of this, the contact may not be located against the locator accurately thereby reducing the functional efficiency of the contact assembly.
An object of the invention is to provide a device for vibrating and accurately locating contacts on base terminals in brazing, which improves bond and bond strength between the contacts and base terminals and increases functional efficiency of the contact assembly.
Another object of the invention is to provide a device for vibrating and accurately locating contacts on base terminals in brazing, which eliminates human errors in locating the contact against the locator.

Another object of the invention is to provide a device for vibrating and accurately locating electrical contacts on base terminals in brazing, which is simple in construction and easy and convenient to operate and does not require the services of a very skilled operator.
According to the invention there is provided a device for vibrating and acurately locating electrical contacts on base terminals in brazing, the device comprising a vertically disposed obtuse angled arm comprising a lower part and an upper part, the lower end of the arm being adapted to abut a contact placed on a base terminal with a fusible material foil or wire interposed therebetween, the base terminal being supported on a fixture and the contact being located against the locator of the fixture, the upper end of the arm being pivotally connected to a drive mechanism for moving the arm up and down, the drive mechanism being supported on a frame mounted on the fixture or on a rigid surface, and a vibrator suppoited on the frame and coupled to the arm to vibrate the arm to and fro horizontally in the direction of the locator.

The following is a detailed description of the invention with reference to the accompanying drawings, in which the sole Fig 1 is a schematic view of a device for vibrating and accurately locating electrical contacts on base terminals in brazing according to an embodiment of the invention.
Referring to Fig 1 of the accompanying drawings, the device 1 comprises a vertically disposed obtuse angled arm 2 (preferably at 120-150°) comprising a lower part 2a and an upper part 2b. The lower end of the arm is adapted to abut a contact 3 placed on a base terminal 4 with a fusible material foil or wire 5 interposed therebetween. The terminal 4 is supported on a fixture 6 whose locator is marked 7. 8 is a pneumatic cylinder supported on a lateral extension 9a of a frame 9 mounted on a rigid surface 10. Alternatively, the fixture may be extended to support the frame. 11 is a piston vertically reciprocating in the cylinder. 12 is a vertically disposed piston rod whose upper end is connected to the piston. 13 is a bracket horizontally disposed and rigidly fixed to the lower end of the piston rod. The upper end of the arm is pivoted on the bracket using a pin 14 rigidly

fixed on the bracket. 15 is a pneumatic direction control valve supported on another lateral extension 9b of the frame 9 and connected to the cylinder side and piston side of the cylinder at 16 and 17, respectively. The valve 15 is also connected to a pneumatic supply line 18. 19 is a magnetic type vibrator comprising an E-shaped magnetic core 20 wound with an electromagnetic coil 21 and located in a housing 22 which in turn is supported on another lateral extension 9c of the frame 9. The coil is connected to a 230 volts AC power supply through a switch 23. 24 is a moving magnet located in the housing in the proximity of the magnetic core. The moving magnet is connected to the inner end of a vibrator rod 25 horizontally disposed adapted to move in and out of the housing. The outer end of the vibrator rod protrudes the housing and is provided with a vibration limiting cum piston rod guiding ring 26 through which the piston rod passes defining a clearance 27 therebetween. The fixture is provided with an oxyacetylene gas or liquified petroleum gas burner 28.
During brazing, the arm is lowered until its lower end abuts and presses against the contact by allowing air flow into the cylinder side by

operating the valve. Simultaneously air at the piston side flows out from the cylinder. Due to air pressure being developed within the cylinder side the piston moves down along with the piston rod, bracket and arm and causes the arm to touch and press against the contact. Because the arm is obtuse angled and its upper end is pivoted, as it touches the contact and the pressure of its hold increases it slowly pushes the contact and locates the contact accurately automatically against the locator. The vibrator is then switched on. Due to the alternating nature of the power supply, the direction of flow of current in the coil changes alternatively and the coil energises and deenergises and assumes opposite polarities intermittently and pulls the moving magnet towards it and repels the moving magnet away from it intermittently. This causes vibration of the. vibrator rod by way of to and fro motion horizontally. Consequently the piston rod and arm vibrate horizontally and the arm moves to and fro in the direction of the locator, about the pivot pin 14 which facilitates the to and fro movement. The contact moves to and fro along with the arm and wiping takes place. After the wiping, the vibrator is switched off and the piston is moved up along

with the piston rod and arm by allowing air to flow into the piston side and air in cylinder side to flow out of the cylinder by operating the valve. Due to air pressure being developed in the piston side, the piston moves up along with the piston rod and arm. The arm is again moved down to press against the contact by operating the valve. During downward travel of the arm, if the contact is not accurately located against the locator, the arm moves the contact towards the locator and accurately locates it against the contactor as described earlier. During wiping the burner is lighted and heating continued until the contact is accurately located and the foil or wire is fully melted. On switching off the burner or removing the burner away from The fixture, the molten foil or wire solidifies and bonds the contact to the terminal. The clearance 27 within the ring limits the amplitude of vibration of the vibrator rod and arm and also guides the piston rod therethrough.
According to the invention the bond and bond strength between the contact and terminal are improved due to mechanical wiping. The functional efficiency of the contact assembly is also improved due to the

contact being accurately located on the terminal. Due to the location of the contact against the locator being automatic, chances of mislocation due to human errors have been eliminated. The device of the invention is simple in construction, easy and convenient to operate and does not require the services of a very skilled operator.
The above embodiment is by way of example and should not be construed to be limitative of the scope of the invention. Several variations of the invention are possible without deviating from the scope thereof. For instance, the cylinder and valve may be operated by another working fluid such as hydraulic fluid. Air is preferred because of cost consideration. The drive mechanism may be of a different construction such as reversible motor and gear drive, in which the motor is actuated electrically, pneumatically or hydraulically. The vibrator may be of a different construction. The arm, piston rod and frame profile may vary. The heat source may be induction or resistance heating. The fixture may have more than one locator and terminal support combination each associated with a device of the invention. Instead of ring 26, a sleeve may be used. The bracket 13 is optional and need not be

horizontal. The upper end of the arm may be directly pivoted on the piston rod. The lower part of the arm may be detachable from the upper part thereof, for instance by detachably fitting in a socket formed at the lower end of the upper part so as to facilitate replacement thereof after wear and tear. Such variations are to be construed to be within the scope of the invention.

We Claim:
1) A device for vibrating and acurately locating electrical contacts on base terminals in brazing, the device comprising a vertically disposed obtuse angled arm comprising a lower part and an upper part, the lower end of the arm being adapted to abut a contact placed on a base terminal with a fusible material foil or wire interposed therebetween, the base terminal being supported on a fixture and the contact being located against the locator of the fixture, the upper end of the arm being pivotally connected to a drive mechanism for moving the arm up and down, the drive mechanism being supported on a frame mounted on the fixture or on a rigid surface, and a vibrator supported on the frame and coupled to the arm to vibrate the arm to and fro horizontally in the direction of the locator.
2) A device as claimed in claim 1, wherein the arm is at 120 to 150°C.
3) A device as claimed in claim 1 or 2, wherein the drive mechanism comprises a piston vertically reciprocating in a cylinder supported on the

frame, a vertically disposed piston rod whose upper end is connected to the piston, a bracket horizontally disposed and rigidly fixed to the lower end of the piston rod, the upper end of the arm being pivoted on the bracket and a direction control valve supported on the frame and connected to the cylinder side and piston side of the cylinder and to a working fluid supply.
4) A device as claimed in claim 3, wherein the cylinder and valve are pneumatically operated and the working fluid supply is pneumatic supply.
5) A device as claimed in any one of claims 1 to 4, wherein the vibrator is magnetic type.
6) A device as claimed in claim 5, wherein the vibrator comprises an E-shaped magnetic core wound with an electromagnetic coil and located in a housing, the coil being connected to an AC power supply, a moving magnet located in the housing in the proximity of the magnetic core, the moving magnet being connected to the inner end of a vibrator rod horizontally

disposed adapted to move in and out of the housing, the outer end of the vibrator rod protruding the housing and being provided with a vibration limiting and guiding ring through which the piston rod passes defining a clearance therebetween.
7) A device for vibrating and accurately locating electrical contacts on base terminals in brazing substantially as herein described particularly with reference to Fig 1 of the accompanying drawings.
Dated this 31st day of May 2000.

(M A Jose) of DePENNING & DePENNING Agent for the Applicants