Title of Invention

CLICK FIT MECHANISM AND DEFEAT MECHANISM IN AN ELECTROMAGNETIC CONTACTOR

Abstract

A click fit mechanism in an electromagnetic contactor adapted to prevent danger of exposing the electrically live parts of control circuit to the operating personnel, the said click fit mechanism comprising plurality of housing assemblies comprising front housing (1) and rear housing (9), said rear housing (9) having erogonomical sidewalls on either sides, a plurality of interlocking means (11a, 12a, 12b, 18, 6, 10) provided in the said housing assemblies in a manner so as to interlock the said front and rear housing (1 and 9) and prevent the said housing to be separated from each other when the supply is switched ON and means (14a and 14b) provided in the said housing adapted to functionally co-operate with the said interlocking means so as to achieve the interlocking during assembly of the housings. A defeat mechanism in the click fit mechanism adapted to defeat/open both click fits simultaneously at a time with the switch being in OFF condition, without using any tool, said defeat mechanism comprising plurality of means (14a, 14b, 15b and 17) being co-operatively engaged with said interlocking means (11a, 11b, 12a, 12b, 18, 6, 10) so as to achieve separation of the front and the rear housing (1 and 9) by disengaging the interlocking means from the rectangular slots (12a and 12b).

Full Text

FORM2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10; rule 13) 1. Title of the invention. - CLICK FIT MECHANISM AND DEFEAT MECHANISM IN AN ELECTROMAGNETIC CONTACTOR 2. Applicant (a) NAME : LARSEN & TOUBRO LIMITED (b) NATIONALITY : 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 : FIELD OF INVENTION The present invention relates to a click fit mechanism in an electro magnetic contactor. More particularly, the invention relates to a click fit mechanism for the housings of the electro magnetic contactor, adapted for preventing the danger of exposing the operating personnel to electrically live parts of control circuit. The present invention also relates to a defeat mechan sm adapted for easy defeating/opening of click fits in the click fit mechanism simultaneously at a time, without using any tool. BACKGROUND ART US 4760364 discloses an enclosure for an electromagnetic contactor is provided with upper and lower housings and a cover over the upper housing, all comprised of molded insulating material. The upper housing is joined ^tc the lower housing by inserting its lugs in notches and rocking it so that a pair of hooks enter corresponding holes at one end and a clamp is pressed over a catch at the other end. A leaf bias spring between the magnet frame and the molded coil applies force to the molded coil which is pressed against the upper housing so that the coil will not morever allows the magnet frame to align with the armature or to move under armature impact, takes up slack between the upper and lower housings, biases the coil rigidly against the upper housing and allows the magnet to move relative to the housings. Blowouts are press-in held in the cover for correct positioning when the cover is assembled. Inclines on the top of the coil guide the return spring into correct centered position when the upper housing is rocked in assembly onto the lower housing. The upper and lower housings, cover, blowouts bias spring and contact carrier are keyed to allow only correct orientation relative to one another in assembly. An alternative version uses another leaf spring between the lower housing and the coil. 2 US 5293521 discloses a protective switch device such as a relay switch provided with at least one pole having contacts that can be separated. It includes a control mechanism that can cause the opening and closing of contacts and that can be actuated by a protective device that can act in case of electrical failure, and a manual control button controlling an electromagnet for operating the contacts. A moving trap door opens and closes an opening of the box so as to make it possible to change the coil of electromagnet. The trap door cooperates with a trap door locking element that can be displaced between a closed position where ;t immobilizes the trap door on the box and an open position making it possible to open the trap door. The trap door locking element is associated with a selective blocking element able to immobilize it in closed position when manual control button occupies all positions other than the stop position and to free it so that a user can bring it into open position, making it possible to open the trap door, when manual control button occupies the stop position. Generally, an electromagnetic contactor comprises an assembly consisting of plastic moulded housing which houses the stationary contacts (also known ?,fixed contacts) and terminals. This assembly also holds another plastic, moulding called contact bridge, which houses the spring loaded contact carriers and an electromagnet. During working of the contactor the contact bridge travels a specific distance along with spring loaded contact carriers and electromagnet. As the spring loaded contact carriers and the electromagnet move during contactor operation, they are popularly known as moving contacts and moving magnet respectively. When the contact bridge is stationary the positions of the moving magnet and moving contacts with respect to contacts secured in the housing are defined precisely in the housing. The moving magnet and moving contacts are held in their respective specific positions by a spring or pair of springs. The springs rest against the contact bridge and are known popularly as return springs. The assembly described above is located in front and hence it is often referred or known as front housing assembly. 3 The electromagnetic contactor also comprises another assembly located in the rear and referred to as the rear housing assembly. The rear housing assembly, consisting of the plastic moulded housing which houses an electromagnet and a coil meant for exciting the electromagnets. The electromagnet in the rear housing assembly does not travel or move during the contactor operation and referred or known as fixed magnet. The position or the fixed magnet in the rear housing assembly is also defined precisely. The other face of return spring is rest against the coil or resting surface in the rear housing assembly. During working of electromagnetic contactor the moving magnet in front housing assembly is attracted towards its magnet in rear housing assembly by giving electric supply to the coil in the rear housing assembly. The moving magnet in front housing assembly moves from its resting position and travel till it meets the fixed magnet.:,i rear housing assembly. As the contact bridge and moving contacts are linked to the moving magnet they also move around the moving magnet. The moving contacts meet the fixed contacts during their travel and a circuit is completed on moving contact touching the fixed contact. This condition viz. when the coil is fed with electric supply and magnet under contacts are closed condition is referred or known as contactor in switched ON condition. When the coil supply is cut-off the retain springs return back the moving magnet an^ hence moving contact and contact bridge to their respective resting positions. This condition viz. when the coil is cut-off and magnets and contacts are in open condition is referred or known as contactor in switched OFF condition. Presently in the contactor housing assembly, the front housing and rear housing are assembled and held together by the click fits or snap fits at two positions. This click fits are located one on either side of front housing assembly or rear housing assembly. 4 Essentially, each click fit comprises of a projection or a groove or slot into which the projection gets locked thus retaining a holding the front housing assembly and rear housing assembly together. During assembly either the projection or wall containing a groove or slot gets flexed and assemblies get locked together once a projection gets locked into the groove or slot provided in the wall. The projections and grooves or slots for locking the same are provided in the moulded front housing and rear housing. It is possible that the projection either in the front housing or rear housing. Similarly the grooves or slots for locking the same can be provided either in front housing and rear housing. The disadvantages with the presently available click fit housing assemblies for electro magnetic contactors are: i. With electric supply to the contactor coils being switched ON, the operating personnel can open the front housing assembly. This is an unsafe condition and the operator may get shock by accidentally touching the live parts of the contactor coil which are exposed due to removal of front housing assembly, with electric supply to the contactor coil being switched ON. ii. Apart from the above safety hazard, defeating of this click fits requires some tool like screwdriver and it is almost difficult to open the front housing assembly without the tool. It also demands for some skill or prior training on part of the operator. iii. The other disadvantage is that one click fit is to be defeated at a time and holding the click fit in open position while opening the second dirk ,'ii:. It is quite common that while opening the second click fit either, the first click fit gets locked again, or the second click fit gets jammed due to tilting. This 5 makes the opening of front housing and rear housing very tedious and time consuming. Thus, there is need for a click fit mechanism in an electromagnetic contactor, which should not allow the opening of front housing assembly or should provide locking of click fit when the electric supply to coil is switched ON, thereby providing safety to operating personnel and a need for defeat mechanism for defeating/opening of click fits in the click fit mechanism without any tools and need to defeat both the click fits, located on either side of housings simultaneously. OBJECTS OF INVENTION Thus the basic object of the present invention is to provide click fit mechanism such that the housing cannot be opened with the electric supply to the contactor coil being switched ON, providing safety to the operating personnel. Another object is to provide a simple and user friendly defeat mechanism for defeating/opening of the click fits provided on front and rear housings without the requirements of any tools or skills by simply pushing the click fits. The other object of the present invention is to provide simultaneous defeating/opening of the click fits provided on housings. SUMMARY OF INVENTION Thus according to the main aspect of the present invention there is provided a click fit mechanism in an electromagnetic contactor adapted to prevent danger of exposing the electrically live parts of control circuit to the operating personnel, the said click fit mechanism comprising: 6 (i) plurality of housing assemblies comprising front housing and rear housing, said rear housing having ergonomical sidewalls on either sides; (ii) a plurality of interlocking means provided in the said housing assemblies in a manner so as to interlock the said front and rear housings and prevent the said housings to be separated from each other when the supply is switched ON; and (iii) means provided in the said housing adapted to functionally co-operate with the said interlocking means so as to achieve the interlocking during assembly of the housings. According to another aspect of the present invention there is provided a click fit mechanism in an electromagnetic contactor comprising a defeat mechanism for defeating/opening both click fits simultaneously at a time with the switch being in OFF condition, without using any tool, said defeat mechanism comprising plurality of means being co-operatively engaged with said interlocking means so as to achieve separation of the front and the rear housing by disengaging the interlocking means from the rectangular slots. DETAILED DESCRIPTION OF INVENTION In the present invention the click fit mechanism comprises plurality of housing assemblies wherein the front housing assembly houses the fixed contacts, terminals and contact bridge. The contact bridge houses the spring loaded moving contact? and is linked to the moving magnet. The front housing assembly also contains return spring, one end of which resting on moving magnet and the other end rests on surface of the coil assembly provided in the rear housing assembly. The said return spring is adapted for returning and maintaining the specific position of the moving magnet and moving contacts when the contactor is in switched OFF or open condition. The rear housing assembly houses the coil assembly and fixed magnet assembly. 7 The front housing assembly comprises a plurality of interlocking means provided in the said housing assemblies in a manner so as to interlock the said front and rear housings and prevent the said housings to be separated from each other when the supply is switched ON. The said means comprises of plurality of strips located on the inner surface of the front housing and have lateral projections at one end and two small slits on either side of the strips forming a very thin wall section at the other end thus providing flexibility to the strip and resilient click fit in the mechanism. The lateral projections comprises first surface having slope and second surface which is in perpendicular relation with the plane of the strip such that it allows easy entry of the projections in the rectangular slots provided in the rear housing. Also the raw material of the front housing (viz. Polyamide 66) is so selected that it has the properties, which will impart the flexibility to the click fit designed as above. The projections are such that they are flexible enough to move for a small displacement while assembling with the rear housing. The rear housing comprises two rectangular shaped slots in the walls ergonomically designed and placed on either side of the rear housing. The rear housing comprises means provided in the ergonomical sidewalls adapted for facilitating entry of the projections during assembly of the front housing and rear housing. The said wall on either side of the rear housing comprises an entry chamfer adapted to facilitate the entry of two click fit projections of front housing assembly while assembling. The click fit projections in the front housing assembly being such that during assembly the front and the rear housing, the projections provide easy locking of the housings. The walls of the rear housing comprise chamfer with predetermined beveled surface adapted for smooth entry of the click fit projections and the said projections due to its own flexibility are collapsed by a small displacement inside the walls of the rear housing. The projections are so provided that after traveling beyond the entry chamfer position in the rear housing wall, the projections flex back towards their normal position i.e. travel out and enter the rectangular slots in the rear housing 8 walls adapted for desired placement of the projections within them. The dimension of the said slots are such that once the projections enter into the slots they get locked into the slots and thus the front housing assembly and the rear housing assembly is held together. For opening of the click fit it is essential that the click fit projections in the front housing are pushed back or displaced to such an extent that these are freed from the slots in the rear housing assembly. The front housing assembly can then be pulled up to separate it from the rear housing. The relative positioning and juxtaposition of the click fit projections with respect to the plurality of electromagnets forming part of the interlocking means and comprising moving electromagnet and fixed electromagnet in the front housing and the rear housing respectively. The said moving and the fixed magnet comprises plurality of limbs wherein each of the limbs of the moving magnet is in magnetic alignment with those of the fixed magnet in a manner that the coil being switched ON the moving electromagnet magnetically coupled with the fixed magnet obstructs the click fit projections from coming out of the rectangular slots. This prevents the click fit projections from getting disengaged/freed from the rectangular slots and thus preventing the front housing from getting disengaged. This ensures safety to the operating person as otherwise he would have been exposed to electrically live parts of control circuit and would have risked an electric shock. However, when the coil supply is switched OFF the moving electromagnet returns back to the open position enabling the projections to move and disengage from the rectangular slots in the rear housing walls. This enables the front housing assembly to get disengaged from the rear housing assembly. The defeat mechanism for the click fit of the present invention comprises means adapted for defeating/opening the plurality of said interlocking means i.e. the projections thus disengaging from the slots and thereby separating the housing 9 assemblies. The said plurality of means comprises of two economically designed, knobs in co-operative engagement with the strips carrying the lateral projections and is adapted for defeating/opening the click fits manually simply by pushing the knobs. The arrangement also comprises springs, one end of which rests on the knob on one side and the other end on the safety shroud fitted to housing so as to achieve resilient press-in/press-out movement of the knob actuating the strip carrying lateral projection to be disengaged from the rectangular slot in the rear housing. The said resilient press-in/press-out movement helps in returning the knob to its initial position. The knobs are located in the safety shrouds attached to the front housing assembly on either side. The knobs comprises oval protruding surface adapted to access and press the knobs simultaneously. The oval surfaces at the other end carry square projections, which in assembled conditions are placed very near, or almost touching the strip in the front housing carrying click fit projections. When the knobs are pressed by fingers, the square projections push the click-fit projections out of their engagement slots and the click fit projections are thus disengaged/freed. Thus the front housing can be separated / disengaged from rear housing. BRIEF DESCRIPTION OF ACCOMPANYING FIGURES Figure 1 illustrates the schematic plan view of the click fit and its defeat mechanism of the present invention. Figures 2(a) and (2b) illustrate the isometric views of the click fit and its defeat mechanism of the present invention. Figure 3 illustrates the schematic plan view of the click fit and its defeat mechanism of the present invention when the electric supply to the coil of the contactor is switched ON. Figure 4 illustrates the detail view X as indicated in figure 3. 10 DETAILED DESCRIPTION OF ACCOMPANYING FIGURES In figure 1 the schematic plan view of the click fit and its defeat mechanism of the present invention is illustrated. The plurality of housing assemblies comprises the front housing (1), which houses the fixed contacts (2), terminals (3) and contact bridge (4). The contact bridge (4) comprises spring loaded moving contacts (5) and is linked to the moving electromagnet (6). The front housing (1) comprises return spring (7) one end of which resting on the moving magnet (6) and the other end rests on surface of the coil (8) situated in the rear housing (9). The moving electromagnet (6) and moving contacts (5) rest at a specific position in the front housing (1) when the contactor is in switched OFF or open condition. The plurality of housing assembly comprises the rear housing (9), which houses coil (8) and fixed electromagnet (10). In figure 1 the two identically shaped strips (18) comprises click fit lateral projections (11a and 11b) at one end the strip (18) and the other end of the strip (18) is made thin forming small slits (19) such that the strips (18) are flexible giving resilient press-in/press-out motion. The lateral projections (11a and 11b) comprises first surface (S1) having slope and second surface (S2) which is in perpendicular relation with the plane of the strip (18) such that it allows easy entry of the projections (11a and 11b) in the rectangular slots (12a and 12b) provided in the rear housing (9) meant for locking click fit projections (11a and 11b) of front housing (1). The rear housing (9) also comprises means provided in the sidewalls comprising entry chamfer (14a and 14b) adapted for facilitating the entry of two click fit projections (11a and 11b) while assembling the front housing (1) and the rear housing (9). The knobs (13a/13b) adapted for defeating click fits (11a/11b) comprises springs (15a/15b) resting in shrouds (16a/16b). In figure 2 the isometric view of the click fit mechanism and its defeat mechanism of the present invention is illustrated. In the figure the front housing (1) and the rear housing (9) are shown in open condition. The projection (11b) gets locked in the 11 rectangular slots (12b). The economically designed spring loaded knob (13b) intended for defeating the click fit and its position with respect to click fit projections is shown. The knob (13b) comprises protruding oval surface at one end and a square projection (17) at the other end which is placed very near to click fit strip (18). It is realizable from figure 2 that when the knob (13b) is pressed it pushes the click fit projection (11b) causing total disengagement from slots (12b). On releasing the knob (13b) the spring (15b) moves the knob (13b) and hence the click fit back to its original position viz. locked condition. In figures 3 and figure 4 (detail view X) the schematic plan view of the click fit and its defeat mechanism of the present invention is illustrated under the condition when the electric supply to the coil of the contactor is switched ON. Under this condition the electromagnets i.e. the moving magnet (6) gets attracted towards the fixed magnet (10). In the figure the moving magnet (6) and the fixed magnet (10) are in a closed position with the electric supply to coil (8) being switched ON. The moving electromagnet (6) occupies a position such that it obstructs the projections (11a and 11b) to come out of or disengage completely from the rectangular slots (12a and 12b). The opening of click fit and housing assemblies is thus prevented when the coil supply is switched ON. 12 WE CLAIM: 1. A click fit mechanism in an electromagnetic contactor adapted to prevent danger of exposing the electrically live parts of control circuit to the operating personnel, the said click fit mechanism comprising: (i) plurality of housing assemblies comprising front housing and rear housing, said rear housing having ergonomical sidewalls on either sides; (ii) a plurality of interlocking means provided in the said housing assemblies in a manner so as to interlock the said front and rear housings and prevent the said housings to be separated from each other when the supply is switched ON; and (iii) means provided in the said housing adapted to functionally co-operate with the said interlocking means so as to achieve the interlocking during assembly of the housings. 2. A click fit mechanism as claimed in claim 1, wherein the interlocking mean1: comprises plurality of strips located on the inner surface of the front housing and having lateral projections at one end and two small slits on either side of the strips wherein the slits forming very thin wall sections at the other end of the strips provide flexibility to the strips producing resilient click fit in the mechanism; said interlocking means further comprising plurality of electromagnets provided in the front and the rear housings in juxtaposition with the said strips. 3. A click fit mechanism as claimed in claim 1 or 2, wherein the lateral projections comprises plurality of surfaces wherein first surfaces having slopes and second surfaces in perpendicular relationship with the plane of the 13 strip in a manner allowing easy entry and locking of the projections in the rectangular slots provided in the rear housing. 4. A click fit mechanism as claimed in any of claims 1 to 3, wherein the plurality of electromagnets comprises moving electromagnet and fixed electromagnet; said moving and the fixed magnet comprising plurality of limbs wherein each of the limbs of the moving magnet is in magnetic alignment with those of the fixed magnet in a manner that the coil being switched ON the moving electromagnet magnetically couples with the fixed magnet preventing the resilient press-in of the projections thus obstructing the click fit projections from coming out of the rectangular slots. 5. A click fit mechanism as claimed in claim 1, where the means in co-operation with the strips carrying lateral projections comprises entry chamfers having predetermined beveled surface in a manner that the lateral projections after traveling beyond the entry chamfer position in the rear housing wall gets flexed back towards their normal position having desired placement in the said rectangular slots. 6. A click fit mechanism as claimed in any preceding claim comprising a defeat mechanism for defeating/opening both click fits simultaneously at a time with the switch being in OFF condition, without using any tool, said defeat mechanism comprising plurality of means being co-operatively engaged with said interlocking means so as to achieve separation of the front and the rear housing by disengaging the interlocking means from the rectangular slots. 7. A click fit mechanism as claimed in claim 6, wherein the plurality of means comprises ergonomically designed knobs in co-operative engagement with the interlocking means comprising strips having lateral projections; said knobs comprising oval protruding surfaces being accessible from outside the front housing and square projections at the other end located in just-touch 14 disengagement of the lateral projections from the rectangular slots by simple press-in motion of the knob separating the front housing and the rear housing. 8. A click fit mechanism as claimed in claims 6 or 7, wherein the knobs comprises springs, one end of the said spring resting on the knob on one side and the other end on the housing so as to achieve resilient press-in-press out movement of the knob actuating the strip carrying lateral projection to be disengaged from the rectangular slots in the rear housing. 9. A click fit mechanism substantially as herein described and illustrated with reference to the accompanying figures. Dated this 20th of June, 2005. Dr. Sanchita Ganguli of S. Majumdar & Co. Applicant's agent 15 ABSTRACT Title : Click Fit Mechanism And Defeat Mechanism In An Electromagnetic Contactor A click fit mechanism in an electromagnetic contactor adapted to prevent danger of exposing the electrically live parts of control circuit to the operating personnel, the said click fit mechanism comprising plurality of housing assemblies comprising front housing (1) and rear housing (9), said rear housing (9) having ergonomical sidewalls on either sides, a plurality of interlocking means (11a, 11b, 12a, 12b, 18, 6, 10) provided in the said housing assemblies in a manner so as to interlock the said front and rear housings (1 and 9) and prevent the said housings to be separated from each other when the supply is switched ON and means (14a and 14b) provided in the said housing adapted to functionally co-operate with the said interlocking means so as to achieve the interlocking during assembly of the housings. A defeat mechanism in the click fit mechanism adapted to defeat/open both click fits simultaneously at a time with the switch being in OFF condition, without using any tool, said defeat mechanism comprising plurality of means (14a, 14b, 15a, 15b and 17) being co-operatively engaged with said interlocking means (11a, 11b, 12a, 12b, 18, 6, 10) so as to achieve separation of the front and the rear housing (1 and 9) by disengaging the interlocking means from the rectangular slots (12a and 12b). Figure 1

Documents:

736-MUM-2005-ABSTRACT(GRANTED).pdf

736-mum-2005-abstract.pdf

736-MUM-2005-ANNEXURE A(11-2-2013).pdf

736-MUM-2005-CLAIMS(AMENDED)-(11-2-2013).pdf

736-MUM-2005-CLAIMS(AMENDED)-(17-8-2011).pdf

736-MUM-2005-CLAIMS(AMENDED)-(25-3-2013).pdf

736-MUM-2005-CLAIMS(GRANTED).pdf

736-MUM-2005-CLAIMS(MARKED COPY)-(11-2-2013).pdf

736-MUM-2005-CLAIMS(MARKED COPY)-(17-8-2011).pdf

736-mum-2005-claims.doc

736-mum-2005-claims.pdf

736-MUM-2005-CORRESPONDENCE(05-05-2010).pdf

736-mum-2005-correspondence(1-7-2009).pdf

736-MUM-2005-CORRESPONDENCE(13-10-2008).pdf

736-MUM-2005-CORRESPONDENCE(15-10-2012).pdf

736-MUM-2005-CORRESPONDENCE(16-2-2009).pdf

736-MUM-2005-CORRESPONDENCE(2-11-2009).pdf

736-MUM-2005-CORRESPONDENCE(25-3-2013).pdf

736-MUM-2005-CORRESPONDENCE(26-7-2010).pdf

736-MUM-2005-CORRESPONDENCE(26-7-2012).pdf

736-MUM-2005-CORRESPONDENCE(IPO).pdf

736-mum-2005-correspondence-received-ver-200605.pdf

736-mum-2005-correspondence-received.pdf

736-mum-2005-description (complete).pdf

736-MUM-2005-DESCRIPTION(GRANTED).pdf

736-MUM-2005-DRAWING(25-3-2013).pdf

736-MUM-2005-DRAWINGS(GRANTED).pdf

736-mum-2005-drawings.pdf

736-mum-2005-form 1(12-8-2005).pdf

736-MUM-2005-FORM 13(25-3-2013).pdf

736-mum-2005-form 18(17-9-2007).pdf

736-MUM-2005-FORM 2(GRANTED).pdf

736-MUM-2005-FORM 2(TITLE PAGE)-(GRANTED).pdf

736-mum-2005-form-1.pdf

736-mum-2005-form-2.doc

736-mum-2005-form-2.pdf

736-mum-2005-form-26.pdf

736-mum-2005-form-3.pdf

736-mum-2005-form-abstract.doc

736-MUM-2005-GENERAL POWER OF ATTORNEY(11-2-2013).pdf

736-MUM-2005-MARKED COPY(25-3-2013).pdf

736-MUM-2005-REPLY TO EXAMINATION REPORT(17-8-2011).pdf

736-MUM-2005-REPLY TO HEARING(11-2-2013).pdf

736-MUM-2005-SPECIFICATION(AMENDED)-(25-3-2013).pdf

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