Title of Invention	A PERMANENT SPLIT TYPE MANDREL FOR USE IN REPEATED MANUFACTURING OF HELICALLY WOUND COMPOSITE PIPES
Abstract	A permanent split type mandrel of variety of shape and dimensions for repetitive use in fabrication/production of helically wound composite pipes of corresponding shapes and dimensions. In particular, the permanent split type mandrel of the present invention is advantageously applied for fabrication procedure involving winding of resin impregnated fibre rovings in manufacturing fibre-reinforced composite pipes/shells having precise winding at a predetermined angle and spacing on the surface of such mandrel so as to favor easy assembling for such fabrication and detachability of the finished pipe/shell from said split type mandrel with application of minimal force in radial direction, in a faster, simpler and cost effective manner, and thus improving productivity and ensuring consistent accuracy and good quality of the part produced.

Title of Invention

A PERMANENT SPLIT TYPE MANDREL FOR USE IN REPEATED MANUFACTURING OF HELICALLY WOUND COMPOSITE PIPES

Abstract

A permanent split type mandrel of variety of shape and dimensions for repetitive use in fabrication/production of helically wound composite pipes of corresponding shapes and dimensions. In particular, the permanent split type mandrel of the present invention is advantageously applied for fabrication procedure involving winding of resin impregnated fibre rovings in manufacturing fibre-reinforced composite pipes/shells having precise winding at a predetermined angle and spacing on the surface of such mandrel so as to favor easy assembling for such fabrication and detachability of the finished pipe/shell from said split type mandrel with application of minimal force in radial direction, in a faster, simpler and cost effective manner, and thus improving productivity and ensuring consistent accuracy and good quality of the part produced.

Full Text	FIELD OF THE INVENTION The present invention relates to a permanent split type mandrel of variety of shapes and dimensions for repeated use in fabrication/production of helically wound composite pipes of corresponding varieties of shapes and dimensions. In particular, the permanent split type mandrel of the present invention is specifically advantageous for carrying out repeated fabrication of pipes involving winding of resin impregnated fibre rovings in manufacturing fibre-reinforced composite pipes/shells having precise winding at a predetermined angle and spacing on the surface of such mandrel and also favor easy detachability of the finished pipe/shell from said split type mandrel. This would enable a faster, simpler and cost effective manner of improving productivity and ensuring consistent accuracy and good quality of helically wound composite pipes. BACKGROUND ART With the expanding globally competitive environment and application of newer technologies, prerequisites like the ability to reduce production cycle time, improve productivity and minimize cost are the essential elements to sustain the fierce competition faced in terms of quantity/volume associated with uncompromising quality of product. Synthetic fibers, plastics and composites are materials finding place to newer applications, substituting traditional materials. Composite pipes/shells are in great demand in industries like the defence, agriculture, aviation and space research. The typical fabrication procedure of such pipes involves precise winding of resin impregnated composite roving at a predetermined angle and spacing on the surface of a mandrel, followed by curing. Conventionally, once cured the cast/wound pipe is either taken out of the mandrel in a tedious way applying requisite force for detachment: with suitable means/apparatus or by collapsing the mandrel permanently. It is known in the related art, that there are normally two types of mandrels in use for fabrication of composite pipes. These are (i) collapsible mandrel made of some fragile materials like fly ash, sand, paper etc. and (ii) single piece metallic permanent type mandrel having a definite taper on the outer surface of the mandrel. Both the above types of mandrels are capable of winding resin impregnated roving on it and curing the wound layers of composite roving. It is, however, experienced in the art that the removal of the cast pipe from these existing conventional configuration of mandrels are either expensive and tedious or involve complex gadget for dislodging the cast component from the mandrel with possibility of inducing error/defects in the product. In some cases such as the collapsible mandrels after the pipe is cast and curec, the collapsible mandrel has to be broken/dissolved for removal of the finished product. This is done either manually or subjecting the finished product wound over the mandrel to a highspeed water jet such that the mandrel collapses releasing the final product safely without any damage. Thus it is apparent that the conventional configuration of mandrels has single product life and for each casting a new core/mandrel is required to be built and used. This makes the entire process of production of composite wound pipes very expensive, time consuming with low productivity. The other type of mandrel used conventionally in the related industry, is made of metal and is of permanent type having fixed near cylindrical shape and geometry. The removal of finished product is accomplished by employing a hydraulic extractor type additional fixture. During removal, the mandrel containing the finished product is unloaded from the centers of winding machine and is mounted on this additional fixture for applying a high axial force. To facilitate removal of cast/wound pipe from the mandrel is often provided with a taper. In spite of presence of the taper, the axial force required to dismantle the pipe from the permanent metal mandrel remain substantially high. The application of force required for detaching the part from the mandrel often inflicts damage on the surface/edge of the cast product, especially at the ends. Because of the high axial force, the end is bulged visibly and distribution of roving tends to be non-uniform. Moreover, the amount, of axial force, which is proportional to the length of the pipe, often induces zones of high stress concentration in the cast product leading to the formation of micro-cracks in it. Under the action of such accumulation of stress, the quality of the composite pipe may further deteriorate in case of low wall thickness. The conventional configurations of mandrel for winding of fibre impregnated roving system thus suffer from the following distinct disadvantages and limitations, needing appropriate remedy: a. Use of collapsible mandrel is expensive and time consuming affecting productivity adversely. b. The force required to remove the existing configuration of permanent mandrel being directly proportional to the length of the cast pipe. c. High axial force, required to remove the product from permanent mandrel inflicts damage by way of formation of end bulge and, creating regions of stress concentration leading to formation of micro cracks. d. An additional hydraulic/mechanical type fixture is required for applying axial force for removal of cast part from the conventional permanent metal mandrel. e. The external surface of existing metallic mandrel, provided with slight taper to facilitate easy dismantling of cast and cured pipe, incorporate unwanted taper in the internal surface of the cast pipe. f. Maintenance cost for the total system is comparatively high due to frequent wear and tear and/or replacement and related downtime to attend to address the same. There has, therefore, been a persistent need in the related art to tide over the limitations of the conventional process of winding fiber impregnated composite roving for formation of pipe using either consumable or fixed type mandrel in a safe and effortless manner to comply with requirements of configuration and quality- standard demanded by different industry segments. A special split type reconfigurable permanent mandrel configuration has been conceived and implemented by way of the present invention in the field of fabricating such composite pipes of varied shape and dimensions, such that the said split type mandrel can be split into a number of parts and thus facilitating removal of the cast and cured composite pipe from the said mandrel without needing excess of axial force for detachment or inflicting any damage or unwanted stress concentration of the composite cast part, at the time of unloading. Importantly, permanent split type configuration of the mandrel would on one hand favor faster removal of product after winding/casting of the composite pipe and on the other hand improve productivity by faster recycling by assembly and reuse of the said permanent type mandrel. OBJECTS OF THE INVENTION It is thus the basic object of the present invention to provide a permanent split type mandrel comprising a plurality of detachable components such as to favor easy removal of the cast/wound and cured composite pipe after curing, in a easy and faster manner without the application of any axial force, so that the same mandrel can be reassembled for reuse to cast a next pipe in sequence at lesser cycle time/set-up time and thereby favoring improved product quality, accuracy and productivity. A further object of the present invention is directed to eliminating any end bulging or crack formation of cast composite pipe due to stress concentration during removal of the cast and cured part/pipe by using the permanent split type reusable metal mandrel according to the invention. A still further object of the present invention directed to permanent split type mandrel configuration for fabrication of resin impregnated roving wound composite pipe directed to eliminate use of any additional fixture to apply axial force to remove the cast/wound and cured pipe from the said split type permanent mandrel. A still further object of the present invention directed to a permanent split type mandrel configuration for fabrication of resin impregnated roving wound composite pipe, so that the same is reused at less set up time thus eliminating the need for single-use consumable mandrel needing longer cycle/changeover time for cast/wound pipe fabrication in batch/sequence. A still further object of the present invention directed to a permanent split type mandrel configuration for fabrication of resin impregnated roving wound composite pipe wherein the wear and tear of individual split components are minimized by eliminating application of any axial force and thus needing less maintenance and related cost, ensuring longer reliable performance. A still further object of the present invention directed to a permanent split type mandrel configuration for fabrication of resin impregnated roving wound composite pipe wherein the dismantling force required is radial in nature and of small magnitude and is thus independent of the length of the cast part/pipe. A still further object of the present invention directed to a permanent split type mandrel configuration for fabrication of resin impregnated roving wound composite pipe wherein the accuracy of split components, individually as well as in combination when assembled, ensure higher dimensional accuracy and surface finish at the inside of the wound/cast and cured pipe, which is attainable even with very small wall thickness of pipe ensuring its safe removal. SUMMARY OF THE INVENTION Thus according to the basic aspect of the present invention, there is provided a permanent mandrel for use in repeated manufacturing of helically wound composite pipes comprising: split type mandrel having releasably fitted plurality of split portions adapted to facilitate the assembling of the mandrel for forming of the pipes of variety of shapes and dimensions and dismantling of the same for release of the formed pipes whereby the same mandrel can be repeatedly used for subsequent castings. Another aspect of the present invention is directed to a permanent mandrel for use in repeated manufacturing of helically wound composite pipes comprising: split type mandrel having releasably fitted plurality of circumferential portions adapted to facilitate the assembling of the mandrel for forming of the pipes and dismantling of the same for release of the pipes whereby the same mandrel can be repeatedly used for subsequent castings. A further aspect of the present invention is directed to said permanent mandrel wherein said split type mandrel comprise two wider channel sections and two narrower channel sections which are adapted to be releasably fitted to selectively define a cylindrical mandrel of desired configuration. A still further aspect of the present invention directed to said permanent mandrel wherein said split portions/channels are releasably secured with respect to each other to define the desired shaped and dimensioned mandrel such that the similar channels face each other. A still further aspect of the present invention directed to said permanent mandrel wherein dowel pins are provided to locate the relative alignments of the different channels having slots formed therein to accommodate spigots for the mandrel assembly. According to yet another aspect of the present invention directed to said permanent mandrel wherein the mandrel comprises two identical narrower channels, outer surfaces of which form parts of the cylindrical surface of the mandrel and having appropriate slots to accommodate the spigots for assembly. A still further aspect of the present invention directed to said permanent mandrel wherein rigid bolts and nuts are provided to secure the assembled mandrel. A still further aspect of the present invention directed to said permanent mandrel wherein said releasable assembly of the mandrel comprising: two flanged hubs mounted on both sides of the mandrel assembly, said flanged hubs being located through their spigot and screwed at both the ends of the mandrel assembly. A still further aspect of the present invention directed to said permanent mandrel comprising post-assembly clamping means adapted to maintain the split assembled parts firmly together and protect the outer surface of the assembled mandrel during handling, which in case of a cylindrical shaped mandrel preferably comprise two annular rings mounted on the mandrel assembly and clamped at the desired position through collar fixing screws. A still further aspect of the present invention directed to a permanent mandrel wherein the said flanged hubs with spigot is adapted for identifying the axis of the mandrel assembly and also facilitate the fixing of the mandrel assembly on the winding machine. According to another aspect of the present invention directed to a method of assembling and disassembling of the mandrel for manufacturing helically wound flexible pipes comprising: steps of assembling comprising: i) bringing together the split channels preferably locating the relative alignment of the different channels in the mandrel assembly by using the dowel pins; ii) relesably fixing the mandrel assembly thus formed of desired shape and dimension; iv) mounting the flanged hubs at the sides of the mandrel assembly with the flanged hubs located preferably through their spigot and screwed at both the ends of the mandrel assembly; v) mounting the clamping means on the mandrel assembly and clamping at desired locations through collar fixing screws, and said steps of disassembling the mandrel comprising: dismantling the mandrel assembly after forming of the pipes thereon by carrying out the steps of : i) releasing the clamping means ; ii) releasing the pair of flanged hubs; iii) releasing the dowel pins, nuts and bolts; and iv) releasing the channels from its assembled position. A still further aspect of the present invention directed to said method of assembling and disassembling of the mandrel for manufacturing helically wound cylindrical flexible pipes comprising: steps of assembling comprising: i) bringing together the two narrower channels and two wider channels in such a way that similar channels face each other; ii) locating the relative alignment of the different channels in the mandrel assembly by using the dowel pins; iii) fixing the mandrel assembly thus formed by nuts and bolts; iv) mounting the two flanged hubs on both sides of the mandrel assembly with the flanged hubs located through their spigot and screwed at both the ends of the mandrel assembly; v) mounting the two annular rings on the mandrel assembly and clamping at desired locations through collar fixing screws, and said steps of disassembling the mandrel comprising: dismantling the mandrel assembly after forming of the pipes thereon by carrying out the steps of : i) releasing the clamping involving the annular rings; ii) releasing the pair of flanged hubs; iii) releasing the dowel pins, nuts and bolts; and iv) releasing the channels from its assembled position. The present invention and its objectives and advantages are described in greater details with reference to the following accompanying non limiting illustrative figures. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES Figure 1: is the illustration of perspective view of the various components of the permanent split type mandrel according to the invention, in dismantled condition. Figure 2: is the illustration of the perspective view of permanent split type mandrel according to the present invention in assembled form. Figure 3: is the photographic image of the permanent split type mandrel of the present invention when mounted on the winding machine in assembled condition. DETAILED DESCRIPTON OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES The present invention is directed to a permanent split type metal mandrel comprising a plurality of components assembled together to generate desired variety of shapes and dimensions of the mandrel to favor winding of impregnated roving in a pre-selected manner on its surface for fabrication of composite pipes of desired shape, dimensions and accuracy. The split type permanent mandrel configuration of the present invention is adapted to simple, accurate and fast assembly and dismantling and thus favoring its multiple use for faster production and reliable quality in a safe mode of dismantling of the cast and cured composite pipe from said mandrel. Reference is first invited to the accompanying Figure 1 that illustrates an exploded perspective view of the permanent split type metallic mandrel in dismantled condition wherein said split type configuration according to the present invention is found to comprise a plurality of components of various shapes and sizes, in a match making relational position. The mandrel shown comprises four channels-two narrower channels (2,11) and two wider channels (8,12), are brought together in such a way that similar channels face each other when assembled. The wider (8,12) and the narrower (2,11) channels having the outer surfaces forming part of the cyl ndrical surface of the mandrel in assembly and are having appropriate slot in each of such channels to accommodate spigots for assembly. Four dowel pins (6) are used to locate the relative alignment of different channels in the mandrel assembly. To provide further rigidity to the assembled mandrel, bolts (5) and nuts (7) are used. Two flanged hubs (9,13) are then mounted on both sides of the mandrel assembly. The flanged hubs are located through respective spigot and screwed at both the ends of the mandrel assembly. Two annular rings (3,10) are then mounted on the mandrel assembly and clamped at the desired location/position through collar fixing screw (1). The mandrel is designed so that after winding of roving and curing, the fabricated composite pipe is extracted eas ly from the permanent split type mandrel. The extraction process can be accomplished very easily by splitting the mandrel into four parts. The splitting process is performed by unlocking the fasteners and applying minor radial force. Once the pipe is taken out, the mandrel can be reassembled for further work. Reference is now invited to the accompanying Figure 2 that illustrates the perspective view of the permanent split type mandrel according to the invention, in assembled position. Narrow (2,11) and wide (8,12) channels are assembled in a manner so that the outer surface of the channels form a strictly cylindrical surface of the mandrel assembly. The channels are furnished with proper fittings in such a way that they can be assembled or dismantled very quickly and accurately. Special machining steps are taken in such a way that any manufacturing inaccuracy will not prevail and all the parts are bound to be assembled accurately. The matching of the split parts are so accurate that even excess resin from the impregnated roving will not be able to sip through the junction of two adjacent pieces. As already described in preceding para, four numbers dowel pins (6) are used to maintain relative alignment of the different in the mandrel assembly and that the Bolts (5) and nuts (7) are used to hold the channels firmly together. Two numbers annular rings (3,10) that snugly fit on the mandrel assembly to provide additional support to the mandrel assembly from outside. Collar fixing screws (1) are used for fixing the annular rings with mandrel assembly. Flanged hubs (9,13) with spigot are used for identifying the axis of the mandrel assembly and at the same time provide the facility for mounting of the mandrel assembly on the winding machine. Six pairs of screws (4) are used that pass through the flanged hubs (9,13) with spigot to fasten them with the channels. According to an important aspect of the invention of the permanent split type mandrel for fabrication of wound/cast composite pipe, the split sections are able to move relatively in the radial directions, the cast product is removed easily by applying radial forces on the component parts. The dismantling force being radial in nature, the magnitude of same need not to be high and is independent of the length of the product. Because of this special feature, casting and removal of thin or very thin composite pipes are accomplished accurately with reliable and consistent quality. Moreover, such a simple and effortless removal process of mandrel from cast and cured pipe virtually eliminates chances of formation of highly stressed region and thereby any induced tendency of crack formation of the final part produced. As already described the permanent split configuration of the reconfigurable mandrel is adapted to faster assembly and dismantling favoring accuracy and quality of wound composite pipe avoiding any damage/distortion and also ensuring reliable operation and higher productivity. Accompanying Figure 3 shows how the assembled permanent split type mandrel is mounted on the winding machine for fabrication of the composite pipe by winding the roving of impregnated fiber over the mandrel in a desired manner. After winding of roving in pre-determined pattern to form the pipe over cylindrical surface of mandrel, it is cured in room temperature and then it is necessary to remove the pipe from the mandrel. The mandrel is so designed that this extraction process can be accomplished very easily by splitting it into four parts. For dismantling the mandrel assembly, the assembly steps should be followed in reverse sequence to release the individual components in sequence. The splitting process is performed by unlocking the fasteners and applying minor radial force. Once the pipe is taken out, the mandrel can be reassembled for further work. It is thus possible by way of the present invention to develop a permanent split type metallic mandrel, adapted to be assembled and dismantled in a simple and faster manner such that the composite pipe produced by winding of impregnated roving over the said split type reusable mandrel, without requirement of any application of axial force of large magnitude using any special hydraulic/mechanical fixture or device. The permanent split type mandrel is having highly accurate configuration such that the pipe fabricated using the mandrel is on one hand provide consistent good quali:y with high level of dimensional accuracy, avoiding any damage caused due to axial force application and resultant end bulging, or crack initiation due to stress concentration in the finished pipe produced and on the other hand ensure faster dismantling and reassembly for reuse of said mandrel, improving the productivity and thus having prospect of wide industrial application in a variety of industries in the related field. WE CLAIM: 1. A permanent mandrel for use in repeated manufacturing of helically wound composite pipes comprising: split type mandrel having releasably fitted plurality of split portions adapted to facilitate the assembling of the mandrel for forming of the pipes of variety of shapes and dimensions and dismantling of the same for release of the formed pipes whereby the same mandrel can be repeatedly used for subsequent cast ngs. 2. A permanent mandrel for use in repeated manufacturing of helically wound composite pipes comprising: split type mandrel having releasably fitted plurality of circumferential portions adapted to facilitate the assembling of the mandrel for forming of the pipes and dismantling of the same for release of the pipes whereby the same mandrel can be repeatedly used for subsequent castings. 3. A permanent mandrel as claimed in claim 2 wherein said split type mandrel comprise two wider channel sections and two narrower channel sections which are adapted to be releasably fitted to selectively define a cylindrical mandrel of desired configuration. 4. A permanent mandrel as claimed in anyone of claims 1 to 3 wherein said split portions/channels are releasably secured with respect to each other to define the desired shaped and dimensioned mandrel such that the similar channels face each other. 5. A permanent mandrel as claimed in anyone of claims 1 to 4 wherein dowel pins are provided to locate the relative alignments of the different channels having slots formed therein to accommodate spigots for the mandrel assembly. 6. A permanent mandrel as claimed in claim 5 wherein the mandrel comprises two identical narrower channels, outer surfaces of which form parts of the cylindrical surface of the mandrel and having appropriate slots to accommodate the spigots for assembly. 7. A permanent mandrel as claimed in anyone of claims 1 to 6 wherein bolts and nuts are provided to secure the assembled mandrel. 8. A permanent mandrel as claimed in anyone of claims 1 to 7 wherein said releasable assembly of the mandrel comprising: two flanged hubs mounted on both sides of the mandrel assembly, said flanged hubs being located through their spigot and screwed at both the ends of the mandrel assembly. 9. A permanent mandrel as claimed in anyone of claims 1 to 8 comprising post-assembly clamping means adapted to maintain the split assembled parts firmly together which in case of a cylindrical shaped mandrel preferably comprise two annular rings mounted on the mandrel assembly and clamped at the desired position through collar fixing screws. 10. A permanent mandrel as claimed in anyone of claims 1 to 9 wherein the said flanged hubs with spigot is adapted for identifying the axis of the mandrel assembly and also facilitate the fixing of the mandrel assembly on the winding machine. A permanent split type mandrel of variety of shape and dimensions for repetitive use in fabrication/production of helically wound composite pipes of corresponding shapes and dimensions. In particular, the permanent split type mandrel of the present invention is advantageously applied for fabrication procedure involving winding of resin impregnated fibre rovings in manufacturing fibre-reinforced composite pipes/shells having precise winding at a predetermined angle and spacing on the surface of such mandrel so as to favor easy assembling for such fabrication and detachability of the finished pipe/shell from said split type mandrel with application of minimal force in radial direction, in a faster, simpler and cost effective manner, and thus improving productivity and ensuring consistent accuracy and good quality of the part produced.

Full Text

FIELD OF THE INVENTION
The present invention relates to a permanent split type mandrel of variety of shapes and
dimensions for repeated use in fabrication/production of helically wound composite pipes
of corresponding varieties of shapes and dimensions. In particular, the permanent split
type mandrel of the present invention is specifically advantageous for carrying out
repeated fabrication of pipes involving winding of resin impregnated fibre rovings in
manufacturing fibre-reinforced composite pipes/shells having precise winding at a
predetermined angle and spacing on the surface of such mandrel and also favor easy
detachability of the finished pipe/shell from said split type mandrel. This would enable a
faster, simpler and cost effective manner of improving productivity and ensuring consistent
accuracy and good quality of helically wound composite pipes.
BACKGROUND ART
With the expanding globally competitive environment and application of newer
technologies, prerequisites like the ability to reduce production cycle time, improve
productivity and minimize cost are the essential elements to sustain the fierce competition
faced in terms of quantity/volume associated with uncompromising quality of product.
Synthetic fibers, plastics and composites are materials finding place to newer applications,
substituting traditional materials. Composite pipes/shells are in great demand in industries
like the defence, agriculture, aviation and space research. The typical fabrication
procedure of such pipes involves precise winding of resin impregnated composite roving at
a predetermined angle and spacing on the surface of a mandrel, followed by curing.
Conventionally, once cured the cast/wound pipe is either taken out of the mandrel in a
tedious way applying requisite force for detachment: with suitable means/apparatus or by
collapsing the mandrel permanently.
It is known in the related art, that there are normally two types of mandrels in use for
fabrication of composite pipes. These are (i) collapsible mandrel made of some fragile
materials like fly ash, sand, paper etc. and (ii) single piece metallic permanent type
mandrel having a definite taper on the outer surface of the mandrel.
Both the above types of mandrels are capable of winding resin impregnated roving on it
and curing the wound layers of composite roving. It is, however, experienced in the art
that the removal of the cast pipe from these existing conventional configuration of

mandrels are either expensive and tedious or involve complex gadget for dislodging the
cast component from the mandrel with possibility of inducing error/defects in the product.
In some cases such as the collapsible mandrels after the pipe is cast and curec, the
collapsible mandrel has to be broken/dissolved for removal of the finished product. This is
done either manually or subjecting the finished product wound over the mandrel to a highspeed
water jet such that the mandrel collapses releasing the final product safely without
any damage. Thus it is apparent that the conventional configuration of mandrels has single
product life and for each casting a new core/mandrel is required to be built and used. This
makes the entire process of production of composite wound pipes very expensive, time
consuming with low productivity.
The other type of mandrel used conventionally in the related industry, is made of metal
and is of permanent type having fixed near cylindrical shape and geometry. The removal
of finished product is accomplished by employing a hydraulic extractor type additional
fixture. During removal, the mandrel containing the finished product is unloaded from the
centers of winding machine and is mounted on this additional fixture for applying a high
axial force. To facilitate removal of cast/wound pipe from the mandrel is often provided
with a taper. In spite of presence of the taper, the axial force required to dismantle the
pipe from the permanent metal mandrel remain substantially high. The application of force
required for detaching the part from the mandrel often inflicts damage on the surface/edge
of the cast product, especially at the ends. Because of the high axial force, the end is
bulged visibly and distribution of roving tends to be non-uniform. Moreover, the amount, of
axial force, which is proportional to the length of the pipe, often induces zones of high
stress concentration in the cast product leading to the formation of micro-cracks in it.
Under the action of such accumulation of stress, the quality of the composite pipe may
further deteriorate in case of low wall thickness. The conventional configurations of
mandrel for winding of fibre impregnated roving system thus suffer from the following
distinct disadvantages and limitations, needing appropriate remedy:
a. Use of collapsible mandrel is expensive and time consuming affecting productivity
adversely.
b. The force required to remove the existing configuration of permanent mandrel
being directly proportional to the length of the cast pipe.
c. High axial force, required to remove the product from permanent mandrel inflicts
damage by way of formation of end bulge and, creating regions of stress
concentration leading to formation of micro cracks.

d. An additional hydraulic/mechanical type fixture is required for applying axial force
for removal of cast part from the conventional permanent metal mandrel.
e. The external surface of existing metallic mandrel, provided with slight taper to
facilitate easy dismantling of cast and cured pipe, incorporate unwanted taper in
the internal surface of the cast pipe.
f. Maintenance cost for the total system is comparatively high due to frequent wear
and tear and/or replacement and related downtime to attend to address the same.
There has, therefore, been a persistent need in the related art to tide over the limitations
of the conventional process of winding fiber impregnated composite roving for formation of
pipe using either consumable or fixed type mandrel in a safe and effortless manner to
comply with requirements of configuration and quality- standard demanded by different
industry segments. A special split type reconfigurable permanent mandrel configuration
has been conceived and implemented by way of the present invention in the field of
fabricating such composite pipes of varied shape and dimensions, such that the said split
type mandrel can be split into a number of parts and thus facilitating removal of the cast
and cured composite pipe from the said mandrel without needing excess of axial force for
detachment or inflicting any damage or unwanted stress concentration of the composite
cast part, at the time of unloading. Importantly, permanent split type configuration of the
mandrel would on one hand favor faster removal of product after winding/casting of the
composite pipe and on the other hand improve productivity by faster recycling by
assembly and reuse of the said permanent type mandrel.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide a permanent split type
mandrel comprising a plurality of detachable components such as to favor easy removal of
the cast/wound and cured composite pipe after curing, in a easy and faster manner
without the application of any axial force, so that the same mandrel can be reassembled
for reuse to cast a next pipe in sequence at lesser cycle time/set-up time and thereby
favoring improved product quality, accuracy and productivity.
A further object of the present invention is directed to eliminating any end bulging or crack
formation of cast composite pipe due to stress concentration during removal of the cast

and cured part/pipe by using the permanent split type reusable metal mandrel according
to the invention.
A still further object of the present invention directed to permanent split type mandrel
configuration for fabrication of resin impregnated roving wound composite pipe directed to
eliminate use of any additional fixture to apply axial force to remove the cast/wound and
cured pipe from the said split type permanent mandrel.
A still further object of the present invention directed to a permanent split type mandrel
configuration for fabrication of resin impregnated roving wound composite pipe, so that
the same is reused at less set up time thus eliminating the need for single-use consumable
mandrel needing longer cycle/changeover time for cast/wound pipe fabrication in
batch/sequence.
A still further object of the present invention directed to a permanent split type mandrel
configuration for fabrication of resin impregnated roving wound composite pipe wherein
the wear and tear of individual split components are minimized by eliminating application
of any axial force and thus needing less maintenance and related cost, ensuring longer
reliable performance.
A still further object of the present invention directed to a permanent split type mandrel
configuration for fabrication of resin impregnated roving wound composite pipe wherein
the dismantling force required is radial in nature and of small magnitude and is thus
independent of the length of the cast part/pipe.
A still further object of the present invention directed to a permanent split type mandrel
configuration for fabrication of resin impregnated roving wound composite pipe wherein
the accuracy of split components, individually as well as in combination when assembled,
ensure higher dimensional accuracy and surface finish at the inside of the wound/cast and
cured pipe, which is attainable even with very small wall thickness of pipe ensuring its safe
removal.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention, there is provided a
permanent mandrel for use in repeated manufacturing of helically wound composite pipes
comprising:
split type mandrel having releasably fitted plurality of split portions adapted to facilitate
the assembling of the mandrel for forming of the pipes of variety of shapes and
dimensions and dismantling of the same for release of the formed pipes whereby the same
mandrel can be repeatedly used for subsequent castings.
Another aspect of the present invention is directed to a permanent mandrel for use in
repeated manufacturing of helically wound composite pipes comprising:
split type mandrel having releasably fitted plurality of circumferential portions adapted to
facilitate the assembling of the mandrel for forming of the pipes and dismantling of the
same for release of the pipes whereby the same mandrel can be repeatedly used for
subsequent castings.
A further aspect of the present invention is directed to said permanent mandrel wherein
said split type mandrel comprise two wider channel sections and two narrower channel
sections which are adapted to be releasably fitted to selectively define a cylindrical
mandrel of desired configuration.
A still further aspect of the present invention directed to said permanent mandrel wherein
said split portions/channels are releasably secured with respect to each other to define the
desired shaped and dimensioned mandrel such that the similar channels face each other.

A still further aspect of the present invention directed to said permanent mandrel wherein
dowel pins are provided to locate the relative alignments of the different channels having
slots formed therein to accommodate spigots for the mandrel assembly.
According to yet another aspect of the present invention directed to said permanent
mandrel wherein the mandrel comprises two identical narrower channels, outer surfaces of
which form parts of the cylindrical surface of the mandrel and having appropriate slots to
accommodate the spigots for assembly.
A still further aspect of the present invention directed to said permanent mandrel wherein
rigid bolts and nuts are provided to secure the assembled mandrel.
A still further aspect of the present invention directed to said permanent mandrel wherein
said releasable assembly of the mandrel comprising:
two flanged hubs mounted on both sides of the mandrel assembly, said flanged hubs being
located through their spigot and screwed at both the ends of the mandrel assembly.
A still further aspect of the present invention directed to said permanent mandrel
comprising post-assembly clamping means adapted to maintain the split assembled parts
firmly together and protect the outer surface of the assembled mandrel during handling,
which in case of a cylindrical shaped mandrel preferably comprise two annular rings
mounted on the mandrel assembly and clamped at the desired position through collar
fixing screws.

A still further aspect of the present invention directed to a permanent mandrel wherein the
said flanged hubs with spigot is adapted for identifying the axis of the mandrel assembly
and also facilitate the fixing of the mandrel assembly on the winding machine.
According to another aspect of the present invention directed to a method of assembling
and disassembling of the mandrel for manufacturing helically wound flexible pipes
comprising:
steps of assembling comprising:
i) bringing together the split channels preferably locating the relative alignment of the
different channels in the mandrel assembly by using the dowel pins;
ii) relesably fixing the mandrel assembly thus formed of desired shape and dimension;
iv) mounting the flanged hubs at the sides of the mandrel assembly with the flanged hubs
located preferably through their spigot and screwed at both the ends of the mandrel
assembly;
v) mounting the clamping means on the mandrel assembly and clamping at desired
locations through collar fixing screws, and
said steps of disassembling the mandrel comprising:
dismantling the mandrel assembly after forming of the pipes thereon by carrying out the
steps of :
i) releasing the clamping means ;
ii) releasing the pair of flanged hubs;
iii) releasing the dowel pins, nuts and bolts; and
iv) releasing the channels from its assembled position.

A still further aspect of the present invention directed to said method of assembling and
disassembling of the mandrel for manufacturing helically wound cylindrical flexible pipes
comprising:
steps of assembling comprising:
i) bringing together the two narrower channels and two wider channels in such a way that
similar channels face each other;
ii) locating the relative alignment of the different channels in the mandrel assembly by
using the dowel pins;
iii) fixing the mandrel assembly thus formed by nuts and bolts;
iv) mounting the two flanged hubs on both sides of the mandrel assembly with the flanged
hubs located through their spigot and screwed at both the ends of the mandrel assembly;
v) mounting the two annular rings on the mandrel assembly and clamping at desired
locations through collar fixing screws, and
said steps of disassembling the mandrel comprising:
dismantling the mandrel assembly after forming of the pipes thereon by carrying out the
steps of :
i) releasing the clamping involving the annular rings;
ii) releasing the pair of flanged hubs;
iii) releasing the dowel pins, nuts and bolts; and
iv) releasing the channels from its assembled position.
The present invention and its objectives and advantages are described in greater details
with reference to the following accompanying non limiting illustrative figures.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the illustration of perspective view of the various components of the
permanent split type mandrel according to the invention, in dismantled condition.
Figure 2: is the illustration of the perspective view of permanent split type mandrel
according to the present invention in assembled form.
Figure 3: is the photographic image of the permanent split type mandrel of the present
invention when mounted on the winding machine in assembled condition.
DETAILED DESCRIPTON OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention is directed to a permanent split type metal mandrel comprising a
plurality of components assembled together to generate desired variety of shapes and
dimensions of the mandrel to favor winding of impregnated roving in a pre-selected
manner on its surface for fabrication of composite pipes of desired shape, dimensions and
accuracy. The split type permanent mandrel configuration of the present invention is
adapted to simple, accurate and fast assembly and dismantling and thus favoring its
multiple use for faster production and reliable quality in a safe mode of dismantling of the
cast and cured composite pipe from said mandrel.
Reference is first invited to the accompanying Figure 1 that illustrates an exploded
perspective view of the permanent split type metallic mandrel in dismantled condition
wherein said split type configuration according to the present invention is found to
comprise a plurality of components of various shapes and sizes, in a match making
relational position. The mandrel shown comprises four channels-two narrower channels
(2,11) and two wider channels (8,12), are brought together in such a way that similar
channels face each other when assembled. The wider (8,12) and the narrower (2,11)
channels having the outer surfaces forming part of the cyl ndrical surface of the mandrel in
assembly and are having appropriate slot in each of such channels to accommodate
spigots for assembly. Four dowel pins (6) are used to locate the relative alignment of
different channels in the mandrel assembly. To provide further rigidity to the assembled
mandrel, bolts (5) and nuts (7) are used. Two flanged hubs (9,13) are then mounted on

both sides of the mandrel assembly. The flanged hubs are located through respective
spigot and screwed at both the ends of the mandrel assembly. Two annular rings (3,10)
are then mounted on the mandrel assembly and clamped at the desired location/position
through collar fixing screw (1). The mandrel is designed so that after winding of roving
and curing, the fabricated composite pipe is extracted eas ly from the permanent split type
mandrel. The extraction process can be accomplished very easily by splitting the mandrel
into four parts. The splitting process is performed by unlocking the fasteners and applying
minor radial force. Once the pipe is taken out, the mandrel can be reassembled for further
work.
Reference is now invited to the accompanying Figure 2 that illustrates the perspective
view of the permanent split type mandrel according to the invention, in assembled
position. Narrow (2,11) and wide (8,12) channels are assembled in a manner so that the
outer surface of the channels form a strictly cylindrical surface of the mandrel assembly.
The channels are furnished with proper fittings in such a way that they can be assembled
or dismantled very quickly and accurately. Special machining steps are taken in such a
way that any manufacturing inaccuracy will not prevail and all the parts are bound to be
assembled accurately. The matching of the split parts are so accurate that even excess
resin from the impregnated roving will not be able to sip through the junction of two
adjacent pieces. As already described in preceding para, four numbers dowel pins (6) are
used to maintain relative alignment of the different in the mandrel assembly and that the
Bolts (5) and nuts (7) are used to hold the channels firmly together. Two numbers annular
rings (3,10) that snugly fit on the mandrel assembly to provide additional support to the
mandrel assembly from outside. Collar fixing screws (1) are used for fixing the annular
rings with mandrel assembly. Flanged hubs (9,13) with spigot are used for identifying the
axis of the mandrel assembly and at the same time provide the facility for mounting of the
mandrel assembly on the winding machine. Six pairs of screws (4) are used that pass
through the flanged hubs (9,13) with spigot to fasten them with the
channels. According to an important aspect of the invention of the permanent split type
mandrel for fabrication of wound/cast composite pipe, the split sections are able to move
relatively in the radial directions, the cast product is removed easily by applying radial
forces on the component parts. The dismantling force being radial in nature, the
magnitude of same need not to be high and is independent of the length of the product.
Because of this special feature, casting and removal of thin or very thin composite pipes
are accomplished accurately with reliable and consistent quality. Moreover, such a simple
and effortless removal process of mandrel from cast and cured pipe virtually eliminates

chances of formation of highly stressed region and thereby any induced tendency of crack
formation of the final part produced.
As already described the permanent split configuration of the reconfigurable mandrel is
adapted to faster assembly and dismantling favoring accuracy and quality of wound
composite pipe avoiding any damage/distortion and also ensuring reliable operation and
higher productivity. Accompanying Figure 3 shows how the assembled permanent split
type mandrel is mounted on the winding machine for fabrication of the composite pipe by
winding the roving of impregnated fiber over the mandrel in a desired manner. After
winding of roving in pre-determined pattern to form the pipe over cylindrical surface of
mandrel, it is cured in room temperature and then it is necessary to remove the pipe from
the mandrel. The mandrel is so designed that this extraction process can be accomplished
very easily by splitting it into four parts. For dismantling the mandrel assembly, the
assembly steps should be followed in reverse sequence to release the individual
components in sequence. The splitting process is performed by unlocking the fasteners
and applying minor radial force. Once the pipe is taken out, the mandrel can be
reassembled for further work.
It is thus possible by way of the present invention to develop a permanent split type
metallic mandrel, adapted to be assembled and dismantled in a simple and faster manner
such that the composite pipe produced by winding of impregnated roving over the said
split type reusable mandrel, without requirement of any application of axial force of large
magnitude using any special hydraulic/mechanical fixture or device. The permanent split
type mandrel is having highly accurate configuration such that the pipe fabricated using
the mandrel is on one hand provide consistent good quali:y with high level of dimensional
accuracy, avoiding any damage caused due to axial force application and resultant end
bulging, or crack initiation due to stress concentration in the finished pipe produced and on
the other hand ensure faster dismantling and reassembly for reuse of said mandrel,
improving the productivity and thus having prospect of wide industrial application in a
variety of industries in the related field.

WE CLAIM:
1. A permanent mandrel for use in repeated manufacturing of helically wound composite
pipes comprising:
split type mandrel having releasably fitted plurality of split portions adapted to facilitate
the assembling of the mandrel for forming of the pipes of variety of shapes and
dimensions and dismantling of the same for release of the formed pipes whereby the
same mandrel can be repeatedly used for subsequent cast ngs.
2. A permanent mandrel for use in repeated manufacturing of helically wound composite
pipes comprising:
split type mandrel having releasably fitted plurality of circumferential portions adapted to
facilitate the assembling of the mandrel for forming of the pipes and dismantling of the
same for release of the pipes whereby the same mandrel can be repeatedly used for
subsequent castings.
3. A permanent mandrel as claimed in claim 2 wherein said split type mandrel comprise
two wider channel sections and two narrower channel sections which are adapted to be
releasably fitted to selectively define a cylindrical mandrel of desired configuration.
4. A permanent mandrel as claimed in anyone of claims 1 to 3 wherein said split
portions/channels are releasably secured with respect to each other to define the desired
shaped and dimensioned mandrel such that the similar channels face each other.
5. A permanent mandrel as claimed in anyone of claims 1 to 4 wherein dowel pins are
provided to locate the relative alignments of the different channels having slots formed
therein to accommodate spigots for the mandrel assembly.

6. A permanent mandrel as claimed in claim 5 wherein the mandrel comprises two
identical narrower channels, outer surfaces of which form parts of the cylindrical surface of
the mandrel and having appropriate slots to accommodate the spigots for assembly.
7. A permanent mandrel as claimed in anyone of claims 1 to 6 wherein bolts and nuts are
provided to secure the assembled mandrel.
8. A permanent mandrel as claimed in anyone of claims 1 to 7 wherein said releasable
assembly of the mandrel comprising:
two flanged hubs mounted on both sides of the mandrel assembly, said flanged hubs being
located through their spigot and screwed at both the ends of the mandrel assembly.
9. A permanent mandrel as claimed in anyone of claims 1 to 8 comprising post-assembly
clamping means adapted to maintain the split assembled parts firmly together which in
case of a cylindrical shaped mandrel preferably comprise two annular rings mounted on
the mandrel assembly and clamped at the desired position through collar fixing screws.
10. A permanent mandrel as claimed in anyone of claims 1 to 9 wherein the said flanged
hubs with spigot is adapted for identifying the axis of the mandrel assembly and also
facilitate the fixing of the mandrel assembly on the winding machine.

A permanent split type mandrel of variety of shape and dimensions for repetitive use in
fabrication/production of helically wound composite pipes of corresponding shapes and
dimensions. In particular, the permanent split type mandrel of the present invention is
advantageously applied for fabrication procedure involving winding of resin impregnated
fibre rovings in manufacturing fibre-reinforced composite pipes/shells having precise
winding at a predetermined angle and spacing on the surface of such mandrel so as to
favor easy assembling for such fabrication and detachability of the finished pipe/shell from
said split type mandrel with application of minimal force in radial direction, in a faster,
simpler and cost effective manner, and thus improving productivity and ensuring
consistent accuracy and good quality of the part produced.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=NNcR2ZLTc5EDcy1JzV9Ekw==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

272891

Indian Patent Application Number

1491/KOL/2008

PG Journal Number

19/2016

Publication Date

06-May-2016

Grant Date

29-Apr-2016

Date of Filing

01-Sep-2008

Name of Patentee

REGISTRAR, BENGAL ENGINEERING AND SCIENCE UNIVERSITY

Applicant Address

SHIBPUR, P. O. BOTANIC GARDEN, HOWRAH

Inventors:

#	Inventor's Name	Inventor's Address
1	DEY, PARTHA	MECHANICAL ENGINEERING DEPARTMENT, BENGALENGINEERING AND SCIENCE UNIVERSITY, SHIBPUR, P. O. BOTANIC GARDEN, HOWRAH-711 103
2	DATTA, DEBASIS	MECHANICAL ENGINEERING DEPARTMENT, BENGALENGINEERING AND SCIENCE UNIVERSITY, SHIBPUR, P. O. BOTANIC GARDEN, HOWRAH-711 103

PCT International Classification Number

F16L 11/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA