A single-stage manufacturing process of fiber reinforced plastic manhole covers

Abstract

A single-stage process for manufacturing Fiber Reinforced Plastic Manhole Covers, Gully Covers, and Recess Covers by using the technique of Close Mould Compression moulding The manufacturing technique comprises a Cover Mould consisting of cavity and back plate (pressure plate) and a Frame Mould consisting of cavity and back plate (pressure plate). The traditional manufacturing process involves numerous steps to manufacture the product and consumes more time, manpower, time, and space. This problem is solved in this current invention by eliminating five intermediate stages and is carried out in one single process thereby saving time, space, manpower, and wastage. Compared to traditional manufacturing processes, Warping and bending are reduced to a minimum, De-bonding / de-lamination is substantially reduced, Mould cycle time is improved and comparatively less skilled manpower can operate the process.

Description

[0001] A SINGLE-STAGE MANUFACTURING PROCESS OF FIBER REINFORCED PLASTIC MANHOLE COVERS

[0002] TECHNICAL FIELD

[0003] This invention relates to a manufacturing process of fiber reinforced plastic manhole covers, Gully Covers, and Recess Covers. This invention particularly relates to a manufacturing process of fiber reinforced plastic manhole covers, gully covers, and recess covers, wherein the covers manufactured from this technique have better strength compared to the traditional methods. This manufacturing process has improved productivity by saving manpower, time, and space and reducing wastage.

[0004] BACKGROUND OF INVENTION

[0005] Patent Application number CN207633373 discloses a continuous fiber reinforced thermoplastic composite manhole cover technical field's a continuous fiber reinforced thermoplastic composite manhole cover, including the virgin metal base, the welding has metal spiro union seat in the inner circle of virgin metal base, from the top down installs planking, honeycomb resistance to compression board and inner panel in proper order in the inner circle of metal spiro union seat, all set up threadedly on planking and the inner panel, planking and inner panel are all through screw thread and metal spiro union seat spiro union, the hole that leaks has been seted up on planking, honeycomb resistance to compression board and the inner panel, the utility model discloses an install the novel well lid assorted fixing base with continuous fibers reinforcing thermo plasticity combined material system on original metal well lid base to realize the combined material well lid and replace the metal well lid and in addition recycle.

[0006] Patent Application number CN105350580 describes a fiber reinforced plastic manhole cover which comprises a circular cover body, wherein rabbets used for being matched with a housing washer fixed on the ground are formed in the periphery of the cover body; through holes and raised edges uniformly distributed on the bottom surface of the cover body are arranged on the cover body; raised reinforcing ribs adopting a cross shape are arranged on the bottom surface of the cover body; and symmetrical triangular ribs are arranged on the two sides of each raised reinforcing rib at intervals. According to the fiber reinforced plastic manhole cover, the raised reinforcing ribs adopting a cross shape are arranged on the bottom surface of the cover body of the manhole cover, and the triangular ribs are arranged on the two sides of each raised reinforcing rib at intervals.

[0007] Patent Application number CN2775141Y relates to a glass fiber reinforced plastic manhole cover for catch basins, which comprises a cover body shaped by glass fiber reinforced plastic material, a seat ring matched with the cover body, and a cover body skeleton composed of steel reinforcement, wherein a supporting beam of the cover body, which is arranged in radial direction and matched with a supporting opening of the seat ring, is arranged below the cover body and shaped into a whole with the cover body, and reinforcing ribs of the supporting beam are provided and matched with the supporting beam. The cover body structure that the reinforcement supporting beam is arranged on the lower part is used in the utility model, and the matching of the supporting beam and the seat ring is used as load bearing support of the cover body to realize the aim that less material is used correspondingly for achieving higher carrying capacity. Compared with the existing similar glass fiber reinforced plastic manhole cover, the utility model has the advantages of strong carrying capacity and low cost. Because the resin, the glass fiber and the quartz sand are used as principal raw material, auxiliary raw material such as reinforcing agent, etc. is added, and the mould shaping and casting technology is used, the utility model is suitable for scale production mode and has the advantage of low cost, and the product can be ensured to have the strength, the toughness, the wear resistant property and the ageing resistance which fully satisfy the operating requirements. Patent Application number 201931030488 relates to a process for manufacturing Reinforced composite manhole cover and in particular, this invention relates to a process for manufacturing Reinforced composite manhole cover in which fiber is reinforced with matrices of thermosetting resin. More particularly, this present invention relates to Reinforced composite manhole cover having the size of 1800 mm (L) X 400 mm (B) X 75 mm (H). Furthermore, this invention also relates to a process for manufacturing Reinforced composite manhole cover has the advantages of high strength, light weight and the like, overcomes the defects of large weight of the traditional metal manhole cover, easy loss, low strength of a concrete manhole cover and the like, and can be used in the fields of municipal engineering, roads and the like.

[0008] The above mentioned inventions are related to manufacturing of fiber reinforced covers, the manufacturing techniques used in these inventions include many steps compared to the current invention. The current invention has reduced the steps required to manufacture the fiber reinforced covers. Multi-stage manufacturing processes followed in these inventions are converted into a single-stage process in the claimed invention thereby improving productivity and saving manpower, time, and space and reducing wastage, also the manufacturing process can be executed with less skilled manpower.

[0009] OBJECT OF THE INVENTION

[0010] The primary object of the invention is to provide a single-stage process for manufacturing fiber reinforced plastic Manhole Covers, Gully Covers, and Recess Covers.

[0011] A further object of the invention is to manufacture the covers with better strength having compact and homogeneous body structures.

[0012] Another object of the invention is to provide improved productivity by saving manpower, time, and space and reducing wastage. SUMMARY OF THE INVENTION

[0013] The traditional manufacturing process of the fiber reinforced plastic manhole covers, gully covers, and recess covers involves numerous steps to manufacture the product, and the process consumes more time, manpower, time, and space, and generates more waste. This problem is solved in the current invention, the manufacturing technique used in this invention eliminates five intermediate stages and is carried out in one single process thereby saving time, space, manpower, and wastage.

[0014] The manufacturing process utilizes a mould cavity having a hinged back plate, where the raw materials - Fibre Glass (CSM), Catalised Resin, Sand Core, Gel coat and slurry are fed inside the mould cavity in a proper sequence and the technique of Close Mould Compression moulding is used to produce the covers. Once the sequential feeding of raw material is completed, the mould is closed using the hinged back plate. The mould is then placed under a hydraulic press and high pressure is applied on the back plate. This high pressure ensures proper compaction and bonding of all the components. The pressure is maintained for specified amount of time till the curing is completed. Upon completion of curing, the pressure is released and the cured component is demoulded. Further flash trimming is done and the finished product is achieved.

[0015] Less skilled manpower can operate this manufacturing process compared to the traditional method. The products made using this new technique have very compact and homogeneous body structures thereby giving the products better strength. This technique has reduced warping and bending to a minimum, also de-bonding / de- lamination is substantially reduced. Hence better finished product is produced using this manufacturing process invention.

[0016] BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 depicts mould cavity having a hinged back plate. Figure 2 depicts Gel Coat applied to the mould surface

[0018] Figure 3 depicts CSM Laying and wetting

[0019] Figure 4 depicts Filling of Msand in the Mould

[0020] Figure 5 depicts closing of mould and pressurizing

[0021] DETAILED DESCRIPTION OF INVENTION

[0022] While the embodiments in the disclosure are subject to various modifications and alternative forms, it should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. It is to be noted that a person skilled in the art would be motivated from the present disclosure and may modify various ingredients, compositions or flow of events of the preparation process, which may vary from application to application. However, such modification should be construed within the scope and spirit of the present disclosure.

[0023] The current invention is related to the process of manufacturing fiber reinforced plastic manhole covers, gully covers, and recess covers by using the technique of Close Mould Compression moulding. The manufacturing technique comprises of: a) Cover Mould consisting of cavity and back plate (pressure plate) b) Frame Mould consisting of cavity and back plate (pressure plate)

[0024] These moulds are made of specially developed plastic. The 3D designing, modelling as well as the CNC machining are all indigenously developed.

[0025] The traditional manufacturing process of the fiber reinforced plastic manhole covers, gully covers, and recess covers involves numerous steps to manufacture the product, and the process consumes more time, manpower, time, and space, and generates more waste. The traditional manufacturing process involves six different stages of production, namely,

[0026] 1) Shell Moulding.

[0027] 2) Trimming.

[0028] 3) Sand Coring.

[0029] 4) Edges Straightening.

[0030] 5) Name Plate.

[0031] 6) Flash trimming and finishing.

[0032] Whereas in the present disclosure, the first five processes of Shell Moulding, Trimming, Sand Coring, Edges Straightening and Name Plate are carried out in one single process thereby saving time, space, manpower and wastages. Steps Involved in the Manufacturing Process of the present disclosure are as below:

[0033] Step 1: Cleaning and applying release agent:

[0034] The mould is laid open on the working table of hydraulic press. Mould is then cleaned and release agent is applied to the inner surface of the cavity (FIG 1-a) as well as the back plate. (FIG 1-b)

[0035] Step 2: Application of Gel Coat:

[0036] A thin layer (about 2mm thick) of Gel Coat is applied to the mould surface (FIG 2). This gel coat gives an aesthetically good finish to the manhole cover. It is then allowed to attain a suitable degree of hardness. This desired hardness is verified manually by touching the gel coat with the tip of finger. The gel coat should have achieved sufficient hardness so as not to stick to the finger.

[0037] Step 3: CSM Faying and wetting: Once the gel coat has attained sufficient hardness, fibreglass in the form of CSM (Chopped Strand Mat), cut of specific size, is laid in the mould as well as the back plate (FIG 3). CSM is laid in a single layer or in multiple layers depending upon the load bearing requirement of the manhole cover. The CSM layers are wetted with catalysed resin.

[0038] Step 4: Filling of M- sand in the Mould:

[0039] Next, measured quantity of m- sand is mixed with catalysed resin in a mixing trough. This mixture of m - sand and resin is poured in the mould cavity and levelled out (FIG 4). Small inserts of EPE foam sheet (2 inch square x 25 mm thick) are placed over the key holes above the levelled out sand surface. These EPE foam inserts create hollow in the finished product where in the lifting handle can be inserted.

[0040] Step 5: Closing of mould and pressurising:

[0041] Once all the raw materials are filled in the mould as per the above sequence, the mould is closed and pressurised in a hydraulic press (FIG 5). The hydraulic press is pressurised from 20 ton to 40 ton based on the size and load bearing requirement of the manhole cover. The pressure is maintained for about 30 minutes so that sufficient curing of the composite material takes place.

[0042] Step 6: De-moulding and flash trimming:

[0043] Pressure is released and the mould is withdrawn from the hydraulic press. It is opened and the finished product is de-moulded. Flash trimming is carried out at all the edges of the cover and further sanding is done to remove any roughness of edges.

[0044] The finished product is the sent for QC check and packing. Less skilled manpower can operate this manufacturing process compared to the traditional method. The products made using this new technique have very compact and homogeneous body structures thereby giving the products better strength. This technique has reduced warping and bending to a minimum, also de-bonding / de- lamination is substantially reduced. Hence better finished product is produced using this manufacturing process invention.

Claims

I / Wc claim,1. A single-stage Manufacturing process of Fiber Reinforced Plastic Manhole covers comprising of, a. Cover Mould consisting of cavity and back plate (pressure plate) b. Frame Mould consisting of cavity and back plate (pressure plate) characterized by a specific flow of events as follows, cleaning and applying release agent, wherein the mould is laid open on the working table of hydraulic press and the mould is then cleaned and release agent is applied to the inner surface of the cavity as well as the back plate;Application of Gel Coat, wherein application of 2mm thick layer of Gel Coat to the mould surface, which is then allowed to attain a suitable degree of hardness;Chopped Strand Mat laying and wetting, wherein fibreglass in the form of Chopped Strand Mat, cut of specific size varying form 150x150 mm to 1100x1100 mm is laid in the mould as well as the back plate and the Chopped Strand Mat layers are wetted with catalysed resin; filling of M-sand in the mould, wherein the measured quantity of m-sand is mixed with catalysed resin in a mixing trough and then this mixture of m-sand and resin is poured in the mould cavity and levelled out and small inserts of EPE foam sheet of 2 inch square x 25 mm thickness are placed over the key holes above the levelled out sand surface, these EPE foam inserts create hollow in the finished product where in the lifting handle can be inserted;closing of mould and pressurizing, wherein the mould is closed and pressurised in a hydraulic press, the hydraulic press is pressurised from 20 ton to 40 ton based on the size and load bearing requirement of the manhole cover and the pressure is maintained for about 30 minutes; de-moulding and flash trimming, wherein the pressure is released and the mould is withdrawn from the hydraulic press, it is then opened and the finished product is demoulded, after which flash trimming is carried out at all the edges if the cover and further sanding is done to remove any roughness of edges.

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