DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates toelectrical and automation industries, and elevated temperature current carryingmechanically loaded components / products for use in electric equipment,and more particularly toafiber reinforcedcomposite material for insulation of the electrical products such as circuit breakers and switchgears and the components thereof.

BACKGROUND

[002] Electrical products such as molded case circuit breakers (MCCB) are used to provide circuit protection in alternative energy, commercial, industrial, mining, and military applications, where they protect against overloads and short circuits in conductors. These circuit breakers are applied in electrical enclosures such as panel boards, switchboards, motor control centers, control panels, combination starters, switchgears devices and individual enclosures. These electrical enclosures have to withstand increased electrical and mechanical stresses. Presently thermosetting material such as sheet molding compound (SMC) is used with glass fibers as reinforcement material.

[003] Currently used thermosetting materials are provided using Injection molding or Compression molding or Transfer molding or Casting processes and/or thermoplastic materials are used with Injection molding or extrusion processes. Such molded components are used in an electrical product. Thermoplastic or thermosetting material components are used in electrical products such as MCCB Housing, Drive Shaft, Trip Plate, Switchboard Bus bar support, ACB Housing, Contactor Housing, Insulating components.

[004] The prior art document,WO 1994029386 A1 discloses a composite material comprising an anisotropic, thermotropic liquid-crystalline polymer matrix and/or a mixture of liquid-crystalline polymer(s) and thermoplastic polymer reinforced with carbon fibers.

[005] The prior art document, WO 2014149014 A1-discloses an apricot seed based composite material that can be processed alike in machine, furniture, construction, aviation, space and defense industry as a base material to be used in light and high mechanic durability elements and parts.

[006] The prior art document, US 8034443 B2 discloses a Plastic composite material made up of a polymer matrix with a concentration of a nanofiber material and with a concentration of graphite-based particles.

[007] The prior art document, US 20140061552 A1discloses a plastic-based composite material capable of conducting electricity and shielding electromagnetic wave.

[008] However, the currently used flame retardant thermos-settingsheet molding compounds (SMC) doesnot give adequate strength in the component with thinner walls. Hence, currently molded SMC components cannot withstand higher short circuit forces for switchgear devices. Also, the currently used thermosetting plastics component manufacturing method where SMC materials are used, there is no specific glass fibers orientation. In absence of which, mechanical strength decreases with lot of variation. This inconsistency of fiber orientation in the polymer composites, especially in the thinner / load-bearing sections of the component, lead to premature failures. With the current technology, it is not possible to manufacture compact electrical products with increased electrical and mechanical stresses coming on their parts. With the current technology, there is a limitation of increasing the strength by increasing the percentage of glass fiber reinforcement as orientation of glass fibers during processing cannot be controlled / consistent. Current compression molding process using SMC does not help to manufacture components of complex shapes or design with higher mechanical strength.

[009] Thus, as the electrical products need to withstand higher short circuit forcesthere exists a need to provide a glass fabric based composite material in combination with SMC thermosetting material that can withstand high mechanical strength along with the desired electrical insulating properties.

SUMMARY OF THE INVENTION

[0010] 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.

[0011] An object of the present invention is to provide a glass fabric based sheet molding compound (SMC) material that provides a greater mechanical strength in electrical products.

[0012] Another object of the present invention is to provide thin walled thermosetting plastics components with 3-dimensional fiber orientation to meet challenging strength demand for the electrical products. Also, it enables to manufacture components of complex shapes or design.

[0013] Accordingly, the present invention provides a glass fabric based fiber reinforce plastic composite material using high percentage of glass fabric based sheet molding compounds (SMCs) with 90o orientation of glass fibersand high percentage of chopped glass SMC material,which provide a desired orientation to the fibers and achieve higher mechanical strength in an electrical product.

[0014] In one implementation, the present invention provides a flame retardant thermosetting component with thinner walls for electrical switching devices to withstand higher short circuit forces.

[0015] In one implementation, the present invention provides a compression molding process with the Glass Fabric SMC technology to achieve consistent higher mechanical strength while maintaining the lower wall thickness.

[0016] In one implementation, the present invention provides thin walled thermosetting plastic components molded using a compression molding process that overcomes the above drawbacks and deficiencies of the existing composites materials.

[0017] Accordingly, in one implementation, a glass fabric based flame retardant (FR) plastics composite material for an insulation comprising at least one secondary sheet molding compound (SMC) material with chopped glasses coupled with at least one base sheet molding compound (SMC) material.

[0018] In one implementation,a component to be used in switch gear comprising at least one secondary sheet molding compound (SMC) material with chopped glasses coupled with a base sheet molding compound (SMC) material for an insulation.

[0019] In one implementation, a component to be used in switch gear for an insulation comprising at least one secondary sheet molding compound (SMC) material with chopped glasses coupled with a base sheet molding compound (SMC) material, wherein the coupling is used as a mould charge.

[0020] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0021] Figure 1 illustrates
A- a charge of Glass Fabric SMC and high glass reinforced SMC,
B- across-section of the part geometry,
C- a composite part developed using the combination of Glass Fabric SMC and high glass reinforced SMC, and
D- a top view indicating the spread of Glass Fabric SMC and high glass reinforced SMC.

[0022] Figure 2 illustratescharge pattern and dimensions charge, and placement in mould cavity, in accordance with an embodiment of the presentinvention.

[0023] Figure 3 illustrates MCCB Drive Shaft in accordance with an embodiment of the present invention.

[0024] Figure 4 illustratesa Glass Fabric based SMC in accordance with an embodiment of the present invention.

[0025] Figure 5 illustrates a self-tapping and strengtheningof the prior-art.

[0026] Figure 6 illustratesMCCB cassette in accordance with an embodiment of the present invention.

[0027] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0028] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0029] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0030] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0031] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0032] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0033] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0034] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0035] In one implementation, thinner / non-uniform geometrical parts compression molded with SMC thermoset material need to withstand high mechanical strength along with the desired electrical insulating properties. Components need to withstand higher short circuit forces. The present invention provides a thin walled thermoset plastics components manufacturing method in which combination of thermoset materials is used thereby improving the fibers orientation to increase mechanical strength, fill intricate shapeof the components to reduce the rejection rate.

[0036] In one implementation, the present invention provides a flame retardant thermoset component with thinner walls for switch gear devices which can withstand higher short circuit forces. Currently used thermoset material (SMC) and process cannot withstand higher short circuit forces due to unpredictable glass fiber orientation, where glass fibers are primarily used as reinforcement. Though high glass reinforced SMC material has higher mechanical strength values on the data sheet, it practically doesnot yield higher mechanical strength on the component level. It is because; higher glass restricts the flow of the material which results in separation of plastics resin and glass reinforcement. As mechanical strength is the combined effect of glass fibers bonded with plastics resin, separation of glass fibers and resin doesnot yield higher strength. With present invention glass fabric based material keeps the glass fibers orientation in the desired direction. This orientation is determined by proper charge pattern and charge weight of the material.

[0037] In one implementation, the present invention provides a new product with new material coupled with modified process, which can be extended for the existing component ofthe existing products to get advantage of the fiber orientation.

[0038] In one implementation, the present invention overcomes the above drawbacks and deficiencies. Despite of the limitations of the component design and mold design, we have developed glass fabric based FR plastics composite material to ensure the desired orientation of the fibers to achieve higher mechanical strength. The orientation and length of the fibers largely increases the mechanical strength of the Plastics component. Thin walled components can be easily molded using conventional processing techniques. Using the present inventions compact electrical products can be manufactured to withstand increased electrical and mechanical stresses coming on their parts. The present invention provides a flame retardant thermoset component with thinner walls for switch gear devices which can withstand higher short circuit forces. With this invention, it help in developing thermoset plastic components manufacturing method in which combination of thermoset materials is used thereby improving the fibers orientation to increase mechanical strength, fill intricate shape of the components to reduce the rejection rate. Also, it is possible to develop a thermoset plastics component with 3-dimensional fiber orientation tomeet challenging strength demand for the product. It enables to manufacture components of complex shapes or design.

[0039] As the thinner / non-uniform geometrical parts compression molded with SMC thermoset material need to withstand high mechanical strength along with the desired electrical insulating properties. The components need to withstand higher short circuit forces In one implementation, the present invention provides a thin walled thermoset plastics components manufacturing method in which combinationof thermoset materials is used thereby improving the fibers orientation to increase mechanical strength, fill intricate shapeof the components to reduce the rejection rate.

[0040] Figure 3 illustrates thedistribution of charge of Glass Fabric SMC in white color and high glass reinforced SMC in Black color. A person skilled in the art will appreciate that for understanding purpose the present invention is explained with the help of MCCB shaft devices however the disclosed method shall not be considered as the limiting factor for the scope of present invention.

[0041] Referring now to figure 4, in one implementation, two strips of existing SMC material of length in-line with Fabric based SMC is placed above & under the Fabric based rolled charge (a sandwich pattern). Weight of Fabric based SMC followed with remaining weight of the normal SMC to be used for sandwich purpose.

[0042] Referring now to figure 2, in one implementation, the first material with higher % glass fabric based SMC (with 90° orientation of glass fibers) is used as a base material and the second material with high % chopped glass SMC is used as a secondary material in order to achieve high strength. The combination of the base materials and the secondary material is used as a mould charge. The charge of pre-defined size and weight is placed in cavity in a specific manner. The two strips of secondary material are placed on the five strips of base material and the whole arrangement is placed in cavity in a U-shape keeping secondary material top side.

[0043] In one implementation, two different SMC materials may be used in combination to achieve- required sufficient strength of components and proper material filling in the small features of components wherein the required strength is achieved by using the specially developed Fabric Based SMC material as the base material. The fabric arrangement of the glass fibers is very stable and it resists to flow at the time of mould closing. This property of glass fabric provides very high strength to the component.

[0044] In one implementation, the issue of less glass filling in small /isolated features due to immobility of glass fabric is overcome using one secondary material introduced in conjunction with base material. This secondary material SMC with Chopped glass was placed on the base Glass Fabric SMC material charge at the locations where glass filling was not proper in components.

[0045] In one implementation, a number of molding trials have been conducted by varying various raw material parameters like glass content, glass fiber arrangement and glass fiber orientation. After the compressive load strength test of all variety of produced components, two materials in combination were decided for final production which comprises:
1. High % glass fabric based SMC with 90° orientation of glass fibers;
2. High % Chopped glass SMC Material

[0046] Referring now to figure 5, in one implementation, the Glass Fabric in multiple layers for a given thickness provides glass fibers orientation in all directions. It facilitates retention of thread profile in components compression molded in SMC with minimal powder formation during repeated screwing and unscrewing operations. Being basic mechanical strength being higher, it shall increase the screw pulling force substantially. In one example, a screw size No. 4 Type Y thread cutting screw (BS 4174) as indicated in figure 4, was used more than 10 times on 2.3 mm thickness. Generally this screw is used for cutting threads in metals and thermoplastic components. And lot of powder formation generally occurs with this type of screw when used on SMC. However, with glass fabric based SMC, powder formation was observed only during thread cutting. In order to get this effect, Glass Fabric based material can be used in sandwiched pattern along with the existing SMC/DMC material or can be placed in stack at respective locations in the mold cavity having a hole meant for self-tapping.

[0047] In one implementation, the electrical product used in the present invention is a MCCB drive shaft.

[0048] In one implementation, a resultant breaking force of new MCCB Cassette compressive strength is provided as :

Cassette Part Flat side Curve side
Cross-sectionArea cm2 ExpectedBreaking loadkgF ActualBreakingLoad Cross-sectionArea cm2 ExpectedBreaking loadkgF ActualBreakingLoad
Left Part 0.192 51 52 0.173 46 52
Right Part 0.225 60 100 0.224 60 100

[0049] For different batches of SMC, the breaking force was found to be varying from 50 kgF to 130 kgF (90 ± 40 kgF).Whereas to meet Short-Circuit test requirement, cassette need to pass 130 kgF. As the glass fiber orientation decides thestrength of the component, with normal SMC it was not possible to achieve higher breaking force and minimal variationwithout increasing the thickness of the cassette.

[0050] To avoid increasing the cassette thickness to make the compact product, glass fabric based SMC material was developedwhere glass fiber orientation is predictable and the material strength is higher due to higher and long glass content. WithGlass Fabric based SMC, we could achieve breaking force of 160 ± 20 kgF.

[0051] As compared to the existing chopped glass based SMC with the combination with Glass Fabric based SMC: MCCBDrive shaftFlexural Load test results are as provided below:
i. the mechanical strength of the MCCB drive shaft is increased by 53%.
ii. the breaking force achieved with Glass Fabric based SMC is 160 ± 20 kgF.
iii. the variation of the SMC material is 61 kg ± 16 kg, which is ±26% variation to ensure glass fiber orientation at the desired shaft location.

[0052] In one implementation, the key process parameters followed during the compression molding may be as provide below:
· Charge pattern: As shown in figure 4, the glass Fabric based SMC rolled keeping length intact and the two strips of existing SMC of length in-line with Fabric based SMC to be placed above and under the Fabric basedrolled charge (a sandwich pattern).
· Charge weight: Weight of fabric based SMC followed with remaining weight of the normal SMC to be used for sandwich purpose.
· Cure Time
· Mold Temperature
· Clamping Pressure

[0053] In one implementation, components molded in glass fabric based SMC materials is used for evaluating short circuit test. High breaking load has made topass the test without any cracks in the components. Fixtures are made to measure the desired breaking load of the componentsusing UTM. Higher flexural breaking load is an indication of using the right material with right process parameters.

[0054] In one implementation, MCCB Drive Shaft components were subjected under Flexural Load Testing. On satisfactory performance, the component is assembled for product testing such as Mechanical Endurance Testing and Electrical Endurance Testing. New material and Process changes is incorporated on the drawing on completing the testing.

[0055] Molding and Testing:
Two different SMC materials were used in combination to achieve-
1. Required sufficient strength of components
2. Proper material filling in the small features of components

The required strength was achieved by using the specially developed Fabric Based SMC material as the base material.

The fabric arrangement of the glass fibers is very stable and it resists to flow at the time of mould closing. This property ofglass fabric provides very high strength to the component. On the other hand, the issue of less glass filling in small /isolated features arises due to immobility of glass fabric.

To address this issue one secondary material introduced in conjunction with base material. This secondary material SMCwith Chopped glass was placed on the base Glass Fabric SMC material charge at the locations where glass filling was notproper in components.

A number of molding trials have been conducted by varying various raw material parameters like glass content, Glassfiber arrangement and glass fiber orientation. After the compressive load strength test of all variety of producedcomponents, two materials in combination were decided for final production which provides higher strength and better glass fiber filling:
1. High % glass fabric based SMC with 90° orientation of glass fibers
2. High % Chopped glass SMC Material

The result of the compressive load strength test done by using above material combination is as follows: Compressive load breaking strength = 150 ± 20 kg

The first material with higher % glass fabric based SMC (with 90° orientation of glass fibers) to be used as a base materialto achieve adequate strength and the second material with high % Chopped glass SMC is used as a secondary material toensure better glass filling in small features.

[0056] Process Parameters:
In one implementation, the trials have been done keeping all other mould parameters constant to achieve better stability of component and lessvariation in component strength. The parameters are -
1. Charge weight
2. Mould Temperature
3. Mould Pressure
4. Mould Closing Speed
5. Cure Time

[0057] Charge Pattern and Placement in Mould cavity:
The combination of two materials may be used as a mould charge. The charge of pre-defined size and weight is placed incavity in a specific manner. The two strips of secondary material may be placed on the five strips of base material andthe whole arrangement maybe placed in cavity in a U-shape keeping secondary material top side.

[0058] For new MCCB with higher breaking capacity, the cassette components molded in presently available SMC material cannotgive desired strength. Hence the components are breaking during short circuit test. Being the compact product, it may notbe possible to increase the thickness of these components. In order to achieve consistent higher mechanical strength whilemaintaining the lower wall thickness, Compression molding process is adopted with the Glass Fabric SMC technology.Though Glass Fabric SMC is expensive compared to the normal SMC, by enlarge the product size decides about the lower consumption of overall Plastics material and hence the cost competitiveness with the following advantages:
1. Compact product design
2. High flexural load with required electrical insulation
3. Overcome inconsistency in composite quality

[0059] In one implementation,a thermoset plastics component with 3-dimensional fiber orientation to meet challengingstrength demand for the product is disclosed. Also, it enables to manufacture components of complex shapes or design.

[0060] In one implementation, a glass fabric SMC can also be used as hybrid solution with existing material in following areas-
· ACB Housing mounting projections to overcome its breakage during transit
· For self-tapping to avoid molded in metal inserts in Switchgear products

[0061] In one implementation, Glass Fabric in multiple layers for a given thickness provides glass fibers orientation in all directions. It may facilitateretention of thread profile in components compression molded in SMC with minimal powder formation during repeatedscrewing and unscrewing operations. Being basic mechanical strength being higher, it shall increase the screw pullingforce substantially.

[0062] In one implementation, a fabric based plastics composite is used in electrical products for Insulation instead of traditional thermoset materials and other thermoplastics material. Components thus produced possess higher mechanical strength while maintaining desired electrical,thermal and flammability characteristics.

[0063] In one implementation, the step wise process in the present invention is as provided below:
1. Layup of combination of chopped glass fabric material with fabric reinforced material of particular size
2. Weighing up the charge to the desired level
3. Shape the entire charge to keep it ready to place inside the mold cavity
4. Clean the mold cavities and punch with compressed air to remove traces of material or flash remaining from the earlier molding cycle.
5. Ensure the desired surface temperature of punch & cavity of the mold
6. Place the material charge quickly inside the mold cavity
7. Close the mold quickly and generate desired clamping pressure to ensure that the mold is completely closed with thin flash around the cavities
8. Keep the mold closed for curing the components for desired time
9. Open the mold slowly followed with slow ejection of the molded components
10. De-flash the component without damaging the part geometry and store it properly for further product assembly.

[0064] It may be noted by the person skilled in that art that, the “FR” is an abbreviation for Flame Retardant. Further, the charge of glass fabric material may be in the strip or roll form or any other form to suit the component geometry and process. In one implementation, the sandwiched pattern of glass fabric material and other chopped glass reinforced materials may be of any numbers and sequence of layer may be altered suitably. The charge pattern of any partial area of the component may also be designed to achieve the desired results. The fabric reinforcement may be of glass or any other suitable polymeric materials. The plastics material may be a thermoset as well as thermoplastics or a combination thereof. The molding process may be compression molding or injection molding or transfer molding or in combination.

[0065] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. Compact product design
2. High flexural load with required electrical insulation
3. Overcome inconsistency in composite quality.
,CLAIMS:1. A glass fabric based flame retardant(FR) plastics composite material for an insulation comprising at least one secondary sheet molding compound (SMC) material with chopped glasses coupled with at least one base sheet molding compound (SMC) material.

2. The glass fabric based flame retardant (FR) plastics composite material as claimed in claim 1, wherein the base material is a fabric based sheet molding compound (SMC) material.

3. The glass fabric based flame retardant (FR) plastics composite material as claimed in claim 1, wherein the base material comprises a higher percentage of glass fabric based SMC, preferably, with 90° orientation of glass fibers.

4. The glass fabric based flame retardant (FR) plastics composite material as claimed in claim 1, wherein the second material comprises a higher percentage the chopped glasses.

5. The glass fabric based flame retardant (FR) plastics composite material as claimed in claim 1, comprises at least two strips of secondary material coupled with at last five strips of base material placed in a cavity in a U-shape keeping secondary material top side.

6. A component to be used in switch gear comprising at least one secondary sheet molding compound (SMC) material with chopped glasses coupled with a base sheet molding compound (SMC) material for an insulation.

7. A component to be used in switch gear for an insulation comprising:
at least one secondary sheet molding compound (SMC) material with chopped glasses coupled with a base sheet molding compound (SMC) material, wherein the coupling is used as a mould charge.

8. The component as claimed in claim 7, preferably comprises at least two strips of secondary material coupled with at last five strips of base material placed in a cavity in a U-shape keeping secondary material top side.

9. The component as claimed in claim 7, comprises a cavity adaptable to receive at least one mechanism of the switch gear.