F0RM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention: AN IMPROVED RIVETED ROTARY JOINT ASSEMBLY
2. Applicant(s):
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001, State
of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is
to be performed:

TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to an improved riveted rotary joint assembly. More particularly, the invention is concerned about a rotary riveted joint assembly which is applicable in switching devices and provides unrestricted motions of the links joined together by using less number of components. Such joint assembly can be assembled in lesser time and is cost effective.
BACKGROUND AND THE PRIOR ART
Air circuit breaker, which is an electrical switching device, is defined as a unit designed to connect, carry, disconnect electrical supply and protect the equipments connected in the electrical circuit from damage caused by overload, under voltage or short circuit etc.
Circuit breaker operating mechanism permits breaker to store energy by compressing springs that are linked to the contact assembly of breaker by latching different links. Stored energy of springs and latching arrangement between the linkages allow breaker to make the contacts, hence completing the electrical circuit (Closing of breaker) as well as break the contacts, hence interrupting the electrical circuit (Tripping of breaker).
Closing and Tripping time of breaker is very crucial in switchgear application as both closing and tripping are done in a very short span of time. Proper distribution of forces is very critical in achieving high speed operation in an operating mechanism of the circuit breaker. Force distribution depends on released energies of various springs used in mechanism along with the way how latching and de-latching is done.
In an operating mechanism of breaker, forces are to be transmitted to the parts/components from one link to another. These forces strongly depend on the profile of components and joints between the links in a subassembly. Latching and de-latching of links mainly depends on how well the assembly is done. This is due to the fact that every part of assembly is under load and system requirement is to have force transmission with minimum losses.

US20040081511 discloses a provision for a riveted attachment for a rotating part, such as for a swiveling handle, is provided using a rivet and two parallel pieces of sheet material. A cylindrical raised dimple with a central through hole is formed in a first piece and that dimple is inserted through a hole in the second piece. A rivet is inserted through the dimple and swaged against opposite ends of the dimple, trapping the second piece while leaving it free to rotate around the cylindrical axis of dimple.
In described circuit breakers, linkage assembly consists of 3 different links as shown in Fig 1(A). These links are latched in two specific orientations resembling closing and tripping operation as shown in Fig (2A and 2B). In application, all the links will be latched and their relative angles are positioned critically such that that even a small degree of angular movement can change the toggle condition. (The dead centre is crossed). Hence force transmission should be efficient and free from losses due to interference between mating parts.
As shown in the Fig (2A and 2B) links are assembled such that in some conditions, they will have relative motion with respect to each other while at other conditions they can move
independently.
In case of normal riveting of two hardened links (up to 48 Re hardness) with a rivet (softer material), there is always a chance of joining of metals due to expansion of soft rivet material inside the holes of links. In such a case, two mating parts becomes single entity and desired
relative motion can't be achieved.
OBJECTS OF THE INVENTION
One object of the present invention is to overcome the disadvantages/drawbacks of the
known art.
Another object of the present invention is to provide an improved riveted rotary joint
assembly.

Another object of the present invention is to use less number of assembling components. Another object of the present invention is to provide a cost effective joint assembly.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
There is provided an improved riveted joint assembly for use in switching devices.
According to one aspect of the present invention there is provided an improved joint assembly, said assembly comprising : first link means having hole means;
second link means having hole means;
roller means is enclosed in said hole of the first link means;
rivet pin means passing through said roller means enclosed in said hole of the first link and said hole of the second link means. Second link means is riveted on protruded roller side of said first link means wherein during riveting process material of rivet pin expands inside said hole of the second link means such that said rivet pin means, roller means and second link means are integrated to form a single body

wherein said roller means having a clearance with said first link means such that in operation said first link means rotates with respect to said rivet pin means, second link means and roller
means.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
So that those having ordinary skill in the art will more readily understand how to construct an improved riveted rotary joint assembly in accordance with the present disclosure, exemplary embodiments are described in details herein below with reference the accompanying
drawings wherein:
Figure 1(A) shows the diagrammatic representation of the linkage assembly and direction of
constrained motion of the links where riveted rotary joints are used.
Figure 1(B) shows the three dimensional view of the same assembly.
Figure 1(C) shows the sectional representation of riveting in the assembly.
Figure 2(A) and 2(B) shows the arrangement of main trip link assembly in breaker ON and
OFF condition respectively.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Referring now to Figure 1(A), Figure 1(B) and Figure 1(C), the like numerals assigned to the parts shown in various figures indicate the like parts.
Referring to Figs. 1 and 2 rivet pin (12) is passed through roller (17) inside first link (13) and hole of second link (15). While riveting, material of rivet pin flares and head is formed on

outer side of second link (15) as shown in Fig 1 (C). During riveting, material of rivet shank expands inside hole of link (15) and rivet (12). Due to this, pin (12), roller (17) and second link (15) are joined together and forms a single body.
Due to clearance between roller (17) and link (13), it behaves as a separate body and hence link (13) can rotate with respect to (12), (15) & (17).
Conventional riveting joins the links permanently with no relative motion of the links. Other alternatives for rotary pin joint needs stepped pin & nut which increase the no. of components & cost. This innovation reduces the no. of components, assembly time & thus cost. Also, importantly it reduces the space requirement.
A hard roller is used in the linkage assembly so that, hard materials are in contact with each other under loading which doesn't lead to seizing. Rivet materials are not hard materials as riveting needs soft, malleable material. Soft materials, in contact with each other lead to
seizing when under load.
According to one embodiment of the present invention, main trip link assembly for the electrical switching device comprises of three links of specific profiles viz. link (11), link (13) and link (15). Link joints (11 & 13) and (13 & 15) are made by riveted rotary joint. Roller (17) is enclosed in the hole of links (11) and (13).
During breaker "OFF" condition (when contacts are not made), the arrangement of trip link assembly would be as shown in Fig 2(A) and when closing command is given, load is coming on link (13) at actuation pt (14) and due to that joints of links (13 and 15) crosses dead centre. At this condition all the links are locked relative to each other. Also when closing command is given, link (18) which is connected to link (15) rotates about its pivot point resulting in motion of moving contacts thus closing the breaker. This is shown by arrangement in Fig 2 (B).

This invention refers to the riveted rotary joint (12). Roller introduced in Rivet joints provides an improved rotary joint which allows unrestricted motions of all the links, which is desired in a mechanism.
The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

WE CLAIM
1. An improved joint assembly, said assembly comprising :
first link means having hole means;
second link means hole means;
roller means is enclosed in said hole of the first link means;
rivet pin means passing through said roller means enclosed in said hole of the first link and said hole of the second link means. Second link means is riveted on protruded roller side of said first link means wherein during riveting process material of rivet pin expands inside said hole of the second link means such that said rivet pin means, roller means and second link means are integrated to form a single body
wherein said roller means having a clearance with said first link means such that in operation said first link means rotates with respect to said rivet pin means, second link
means and roller means.
2. Assembly as claimed in claim 1 wherein said roller means having width more than said first link means.
3. An improved joint assembly as herein described and illustrated with reference to accompanying drawings.