FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - FINGERPROOF CONTACT SYSTEM FOR
DRAWOUT TYPE ASSEMBLIES
2. Applicant
(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 :

Field of the invention
The present invention relates to a finger proof electrical contact system. More particularly, the invention relates to a contact system comprising draw-in-draw-out type assemblies for providing optimum contact pressures where the assemblies of the contact system being so designed that the contact elements are at same horizontal level thereby making the contact system compact.
Background and prior art
Contact systems are used in switchboards, circuit breakers and the like for use in electrical power distribution network. Contact systems maintain the continuity and discontinuity in a power network. One of the greatest concerns in the power distribution network is to provide sufficient and adequate protection to the equipments particularly at maintenance position connected to the power circuit/network.
However, modules/ trolleys (draw out assemblies) currently existing in the art and used in switchboards are becoming more and more dense as well as require a number of auxiliary contacts.
US4020301 describes a drawout mechanism which includes a carriage mounting a circuit breaker and supported on telescoping rails to facilitate racking movement of the circuit breaker between extreme positions of electrical engagement and disengagement with respect to switchboard primary disconnect contacts. In an intermediate test position, the primary contacts are disengaged but plural secondary contacts mounted by the carriage and by the switchboard are engaged for testing of accessorial functions. The plural switchboard secondary contacts are floatingly mounted such that they can be drawn en masse into contact engaging alignment with the plural circuit breaker secondary contacts as the carriage moves into the test position from the disengaged position. This mechanism comprises spring. This patent however does not teach a compact, finger proof device
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without the use of a spring. The mechanism as described in this patent document is much complex to be assembled.
US5176529 describes a device for connecting control current lines in low voltage switchboard plants. The device should allow the control current in a plug-in distribution board to be easily maintained up to a test position of the rack and to be cut beyond this position when the rack is drawn out. The device has two multipoint plugs with plugs and sockets, of which the first is rigidly linked to the rack and the other is movably mounted over a limited path on two guiding pins, the terminal cross-section of which is enlarged. In the test position they are locked in by elastic elements, ensuring complete contact between both multipoint plugs in this position when the rack is inserted. A plurality of control lines can be easily cabled with little attrition in a reduced space within a plug-in distribution board and a test position can be reached by drawing out the rack. This device uses a spring element which causes catching of the movable contact strip. It has not taught a finger proof compact device which would be able to provide optimum contact pressure and that too without using any spring.
US6806424 discloses connecting terminal for switching device includes at least one receiving device configured to interchangeably receive either of a base contact element for a screw connection or a module for a spring-clamping device. A receiving shaft configured to engage the module is provided. The module includes an open mounting side configured for mounting the spring-clamping device.
US5434369 describes an automatic secondary disconnect mechanism for an electrical switchgear apparatus having an enclosure and a removable circuit device is disclosed. Automatic secondary disconnect mechanism comprises a guide rail mounted to the enclosure so as to extend substantially parallel to the racking motion of the circuit device; a slide member slidably mounted on the guide rail; apparatus for locking the slide member in place on the guide rail at a point corresponding to a test position of the circuit device; and apparatus for releasing the slide member when the circuit device reaches the test position from the disconnect position. One of a pair of mating secondary contact
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members is coupled to the slide member, while the other mating contact member is coupled to the circuit device. The mating secondary contact members automatically engage as the circuit breaker moves from the disconnect position to the test position, remain engaged and move together via the slide member as the circuit breaker moves between the test and connect positions, and automatically disengage as the circuit breaker moves past the test position toward the disconnect position. This patent does not teach any such construction which would make the arrangement compact by placing contacts at the same horizontal level.
In the prior art and the existing contact system comprises springs, separate guiding components which make the assembly of the system complex and making of the system is also expensive.
Thus there is a need to provide for a contact system comprising draw-in-draw-out type assemblies for providing optimum contact pressures without using any spring and where the assemblies of the contact system being so designed that the contact elements are at same horizontal level making it compact and which can provide IP2X protection (finger proof) for safety of human being while working on it.
The present inventors have now found that a unique construction of draw out type assemblies can be provided in a contact system which would enable optimum distribution of pressures between the contacts of the contact system and too without use of springs and is so designed that the contact elements would be located at same horizontal level making the system more compact and has an inbuilt IP2X protection.
Objects of the invention
It is one of the objects of the present invention to overcome the disadvantages prevailing in the prior art.
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Another object of the present invention is to provide contact system comprising unique construction of draw-in-draw-out assemblies which could provide optimum contact pressure without use of any spring.
Another object of the present invention is to provide inbuilt facility in the contact such that it can take care of any vertical tolerance without using any separate guiding components.
Another object of the present invention is to provide design of the draw out assembly such that the contact elements are located at same horizontal level thereby saving space and making the system more compact and cost effective.
Another object of the present invention is to provide stacking arrangement in the contact for stacking any number of contact systems as required without use any attaching means like screw, soldering/welding of the contact system and the like.
Another object of the present invention is to provide IP 2X protection at all positions of drawout assemblies which can assure safety of human being working on system.
Summary of the invention
Accordingly, one aspect of the present invention is to provide a contact system for providing optimum contact pressure, said system comprising
plurality of contact assemblies, said assemblies include contact assembly I and contact
assembly II, wherein
said contact assembly I comprising
a housing;
communicating means protruding out of the housing to a predetermined length so as to
aid in sliding motion of the contact assembly I into contact assembly II;
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plurality of contact elements being partially secured in the housing with a predetermined
portions of contact elements in juxtaposition with said communicating means, wherein
the contact elements being profiled in a manner to provide rigidity to the contact
assembly;
wherein said contact assembly II comprising
a housing;
plurality of contact elements being secured in the housing, wherein said contact elements
being such that insertion and guiding of contact assembly I into contact assembly II while
draw-in-draw-out operation is facilitated.
According to another aspect of the present invention there is provided a contact system for providing optimum contact pressure comprising
plurality of contact assemblies, said assemblies include contact assembly I and contact
assembly II, wherein said contact assembly I being slidably located in cooperation with
contact assembly II which is stationary
wherein
said contact assemblies I and II comprises
a housing;
position guiding means having projection element substantially in a vertical direction to
the surface of the housing
plurality of projections located on the housing surface wherein the housing have
predetermined slots such that on placing at least one stationary contact assembly on
another stationary contact assembly or at least one slidable contact assembly on another
slidable contact assembly, stacking of the assemblies is obtained.
Detailed description of the invention
In the present invention contact system comprises plurality of contact assemblies which include contact assembly I and contact assembly II. The contact assembly I and contact
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assembly II comprises housings having plurality of projections located superficially on the housings. The said projections are provided so as to provide stacking of other similar housings easily. At least one similar stationary contact assembly can be stacked with the contact assembly I (hereinafter referred to as "male contact assembly") and at least one slidable contact assembly can be stacked with the contact assembly II (hereinafter referred to as "male contact assembly"). The housings also comprise position guiding means having projection elements (hereinafter referred as "male position guide") located in substantially vertical directions on the surfaces of housings which co-operatively dispose in grooves (hereinafter referred to "female position guide") provide on the other side of the housings adapted to provide appropriate position location when housings are placed one above the other. The sidewalls of the housings are provided with predetermined slotted profile such that when the housings are the placed one above the other and pressed the projections slips into the slotted profile and click fits into the slotted profile. Communicating means comprising elongated limb portion protruding out of the housing to a predetermined length. This communicating means aids in sliding motion of the male contact assembly into female contact assembly. The communicating means is provided with plurality of flanges on which plurality of contact elements are juxtaposed being partially secured in the housing.
One embodiment of the present invention describes male contact assembly I comprising contact elements which include male contact element I and male contact element II. Male contact element I comprises rounded bent portion having predetermined radius of curvature and a sharp bent rectangular surface comprising an aperture which allows entry of screw for fixing the contact element I. The radius of curvature of the rounded bent portion of the male contact element is such that it facilitates guiding and mounting inside the housing and provides rigidity to the contact elements. The sharp bent rectangular surface is fixed to the walls of the housing by screw means. However, this way of fixing by screw means do not restrict the scope of the invention and any other way of fixing the contact element to the walls of the housing will serve the purpose. The other male contact element II resting on the other flange of the communicating means comprises of similar rounded bent portion having predetermined radius of curvature and a sharp bent
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rectangular surface comprising an aperture which allows entry of screw for fixing the contact element II. The housing of the male contact assembly is also provided dips which provides additional support for accommodation of the contact elements.
Another embodiment of the present invention describes female contact assembly II comprising contact elements which include female contact element I and female contact element II. Female contact element I comprises substantially L-shaped profile having at one end plural semi-circular plates of appropriate predetermined radius of curvatures and at the other end comprises a rectangular projection having an aperture which allows entry of screw for fixing the contact element I to the walls of the female contact assembly. However, this way fixing by screw means do not restrict the scope of the invention and any other way of fixing the contact element to the walls of the housing will serve the purpose. The radius of curvatures of the semi-circular plates of the female contact element is such that it maintains a predetermined gap between the two semi-circular plates so as to absorb vertical tolerance of ± 2 mm and to facilitate easy guiding and insertion of male contact assembly I while draw-in-draw-out operation of the assemblies. The other female contact element II comprises a substantially C-shaped profile having similar plural semi-circular plates aiding in the absorption of vertical tolerance of ± 2 mm.
Yet in another embodiment the housing of the contact assemblies I and II comprises slots for holding wire lugs.
Brief description of the accompanying drawings
Figure 1A illustrates the contact system of the present invention with stacked the stationary and the moving assemblies in isolated position.
Figure IB illustrates the contact system of the present invention with the stacked stationary and the moving assemblies at service position.
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Figure 2 illustrates the disassembled view of the moving contact assembly I (male contact assembly) of the present invention.
Figure 3 A illustrates an isometric view of the moving contact assembly I (male contact assembly) of the present invention.
Figure 3B illustrates an isometric view from the other side of the moving contact assembly I (male contact assembly) of the present invention.
Figure 4A illustrates the assembled view of the moving contact assembly I (male contact assembly) of the present invention and stacking of the moving contact assembly I with another similar moving contact assembly I.
Figure 4B illustrates the assembled view of the stationary contact assembly II (female contact assembly) of the present invention and stacking of the stationary contact assembly II with another similar stationary contact assembly I.
Figure 5 illustrates the disassembled view of the stationary contact assembly II (female contact assembly) of the present invention.
Figure 6A illustrates an isometric view of the stationary contact assembly II (female contact assembly) of the present invention.
Figure 6B illustrates an isometric view from the other side of the stationary contact assembly II (female contact assembly) of the present invention.
Figures 7A(i) and 7A(ii) illustrate isometric views of male contact element I and male contact element II respectively of the present invention.
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Figures 7B(i) and 7B(ii) illustrate isometric views of female contact element I and female contact element II respectively of the present invention.
Detailed description of the accompanying drawings
The invention will now be illustrated with reference to accompanying drawings, which are provided for ready and better understanding of the invention. The drawings represent only a specific working embodiment of the assembly according to the invention although variants of the assembly may be made within the scope and ambit of the present invention.
Figure 1A shows the stationary contact assembly II (part 2, as shown in figure IB) and moving contact assembly I (part 1 as shown in figure IB) in stacked condition. Referring to both figures 1A and IB the moving contact assembly I (male contact assembly) comprises male contact element I (1A) and male contact element II (IB) and housing (1C). The stationary contact assembly II (female contact assembly) comprises female contact element I (2A), female contact element II (2B) and housing (2D).
In figure 2 disassembled view of the moving contact assembly I is shown. Male contact element I (1A) (also shown in an enlarged view in figure 7A(i)) and male contact element II (IB) (also shown in an enlarged view in figure 7A(ii)) comprises rounded bent portion (3A) which has a predetermined radius of curvature as already discussed hereinabove. The contact elements (1A and IB) comprise sharp rigid bent portions (3B) having apertures (3D). The communicating limb (1J) comprises flanges (1R) on which the contact elements (1A and IB) are juxtaposed.
In figures 3 A and 3B the housing (1C) of the contact assembly I along with its stacking arrangements are shown. The housing comprises plurality of projections (1H and IK) and male position guide (1G) and slots (1M) for proper stacking of the assemblies. Projections (1H and IK) slip into the slot (1M) and provide click fitting one male contact assembly with another. The housing (1C) also comprises female position guide (IF).
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Housing (1C) additionally comprises of mounting projections (IN). Dips (IP) are provided in the housing for accommodating the contacts.
In figure 5 female contact assembly II comprises female contact element I (2A) (also shown in an enlarged view in figure 7B(i)) and female contact element II (also shown in an enlarged view in figure 7B(ii)). Female contact element I (2A) comprises semicircular plates (3C) and at the other end a rectangular projection (3D) having an aperture (3E) which allows entry of screw for fixing the contact element I to the walls of the female contact assembly. There is a predetermined gap (3F) ((also shown in an enlarged view in figure 7B(i)) between the two semi-circular plates (3C) so as to absorb the vertical tolerance. Female contact element II (2B) comprises similar plural semi-circular plates (3C) aiding in the absorption of vertical tolerance.
In figures 6A and 6B the housing (2D) of the contact assembly II along with its stacking arrangements are shown. Housing (2D) comprises plurality of projections (2H and 2K) and male position guide (2G) and slots (2M) for proper stacking of the assemblies. Projections (2H and 2K) slip into the slot (2M) and provide click fitting one female contact assembly with another. The housing (2D) also comprises female position guide (2F). Housing (2D) additionally comprises of mounting projections (2N).
Advantages :
1. Housing of both contact assemblies I and II are designed in such way that it preferably encloses main contacts from all sides providing IP 2X protection (finger proof).
2. The contact system of the present invention is compact, the two contact assemblies viz. the male contact assembly and the female contact assembly being located in the same horizontal level. Size of the contact system is almost half of conventional contact system.
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3. Assembly time is less compared to the conventional contact system.
4. Can be fitted along with all types of draw out modules and switching devices.
5. Any number of contact systems can be stacked without use of any complex attaching means.
6. Optimum pressure in the contacts without use of any springs.
The invention has been shown and described in a preferred form only and many variations may be made in the invention, which will still be comprised within its spirit. It is understood, therefore, that the invention is not limited to the details cited above. The gaps between semi-circular plates, fixing of contact elements in the housing as herein described do not limit the scope of the present invention. The same can be replaced by its technical equivalence and yet the invention can be performed. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.
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We claim
1. A contact system for providing optimum contact pressure, said system comprising
plurality of contact assemblies, said assemblies include contact assembly I and
contact assembly II, wherein
said contact assembly I comprising
a housing;
communicating means protruding out of the housing to a predetermined length so
as to aid in sliding motion of the contact assembly I into contact assembly II;
plurality of contact elements being partially secured in the housing with a
predetermined portions of contact elements in juxtaposition with said
communicating means, wherein the contact elements being profiled in a manner
to provide rigidity to the contact assembly;
wherein said contact assembly II comprising
a housing;
plurality of contact elements being secured in the housing, wherein said contact
elements being such that insertion and guiding of contact assembly I into contact
assembly II while draw-in-draw-out operation is facilitated.
2. A contact system as claimed in claim 1, wherein the contact elements of contact assembly I comprise rounded bend portion having radius of curvature so as to facilitate guiding and insertion of the contact elements into the housing.
3. A contact system as claimed in claim 2, wherein the contact elements further comprise sharp rigid bent portion adapted to reduce pressure exerted by lugs and cables on the contact assembly.
4. A contact system as claimed in claim 1, wherein the communicating means comprises elongated limb having plural flanges.
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5. A contact system as claimed in claim 1, wherein the contact elements of contact assembly II comprises plurality of semi-circular plates having predetermined gap in between so as to facilitate easy insertion of contact elements of male contact assembly while draw-in-draw-out operation.
6. A contact system as claimed in 5, wherein the semi circular plates provides absorption of vertical tolerance ranging from +2mm to -2mm.
7. A contact system for providing optimum contact pressure comprising
plurality of contact assemblies, said assemblies include contact assembly I and
contact assembly II, wherein said contact assembly I being slidably located in
cooperation with contact assembly II which is stationary
wherein
said contact assemblies I and II comprises
a housing;
position guiding means having projection element substantially in a vertical
direction to the surface of the housing
plurality of projections located on the housing surface wherein the housing have
predetermined slots such that on placing at least one stationary contact assembly
on another stationary contact assembly or at least one slidable contact assembly
on another slidable contact assembly, stacking of the assemblies is obtained.
8. A contact system as claimed in claim 7, wherein the position guiding means further comprises predetermined grooves so as to provide insertion of projection element into it thereby appropriately locating the contact assemblies during stacking.
9. A contact system as claimed in claims 7 and 8 additionally comprising mounting projections so as to provide easy assembly of the housing on metal structures.
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10. A contact system for providing optimum contact pressure as substantially herein described and illustrated with reference to accompanying figures.

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ABSTRACT
TITLE: FINGERPROOF CONTACT SYSTEM FOR DRAWOUT TYPE ASSEMBLIES
The present invention relates to a fingerproof contact system for providing optimum contact pressure. The system comprises plurality of contact assemblies which include contact assembly I (PART I) and contact assembly II (PART II). Contact assembly I comprises a housing (1C), communicating means (U) protruding out of housing (1C) to a predetermined length so as to aid in sliding motion of the contact assembly I into contact assembly II, plurality of contact elements (1A and IB) being partially secured in the housing (1C) with a predetermined portions of contact elements (1A and IB) in juxtaposition with said communicating means (IJ). Contact assembly II comprises housing (2D), plurality of contact elements (2A and 2B) secured in the housing (2D) in a manner that insertion and guiding of contact assembly I into contact assembly II while draw-in-draw-out operation is facilitated. Housings (1C and 2D) comprise projections (IH, IK, 2H and 2K) and slots (IM, 2M) which facilitate stacking of one housing with another.
Figure 1A & 3B