the connector according to the present invention and shown in fig2 a has the basic construction properly depicted in the form of a sectional drawing . a connector 10 comprises the following three sections : a top section a which is to be inserted into the inner portion of the connecting section of a pipe , an intermediate section b , and a rear section c which extends to the outside of the connecting end . the external diameter of the intermediate section b , as well as that of the top section a , is so selected as to be less than the inner diameter of the pipe , thus making it easy enough to be inserted into the inner section of the connecting section in a proper manner . the rear section c has such an inclination 12 as to enable the outer diameter of the the connecting end to increase in a gradual manner relative to the inner diameter , and has a flange 11 properly formed at the final stage . the top section a has a primary ejection ring section 14 properly formed thereon , has a secondary ejection ring 13 properly formed at virtually the center of the intermediate section b , and has the external periphery formed into a ring - shaped groove 13a . the external peripheral section 14a of the primary ejection ring section 14 constitutes a step which projects from the intermediate section b . the section shown in fig2 b is a basic example of the connector made of a pipe member . the top section a has an ejection ring 140a properly fitted in place into such a ring - shaped flange 140 of a smaller diameter which steps down , whereby the primary ejection ring section 14 is thus properly formed . the intermediate section b has a ring - shaped concave section 130 properly formed at a position rather near the top section of the center thereof , and the external periphery has a packing member 130b like a rubber ring of the like properly fitted in place in a ring - shaped groove 130a which is formed thereon . the rear section c has a step 120 which is engaged with an open edge of the connecting end of the pipe properly formed thereon , and furthermore , has a flange 110 formed by bending the pipe . the intermediate section b is provided with a gentle slope which runs to the top section a from the step section 120 . this state is discerned in the sectional drawing thereof in fig2 b and represents the condition at the time of being inserted into a heat insulation pipe as shown in fig4 a . the sequence of fitting the connector shown in fig2 in place into a heat insulation pipe 15 is shown in fig3 a through fig3 c . the heat insulation pipe 15 has a heat insulation layer 15c made of hard vinyl chloride as is properly put on a thin stainless steel pipe 15a as a cover in a secure manner . a clearance x 0 is formed between the intermediate section b and the pipe - connecting end of the connector , and insertion into the connecting end of the connector can be conducted readily enough in such manner as is shown in fig3 a . the secondary ejection ring section 13 has a rubber ring 13b properly fitted in place into the external peripheral groove 13a thereof . fig3 b shows a state wherein only the primary ejection ring section 14 is subjected to the treatment for expanding the diameter . the inner diameter of the primary ejection ring section 14 is less than that of the secondary ejection ring section 13 and , the expansion of the diameter is conducted in such a sequence that the primary ejection ring section is first subjected to the expansion , and in the wake thereof the primary ejection ring section is further subjected to expansion concurrently with the expansion of the diameter of the secondary ejection ring section , in two steps . the tools required for expanding the diameter are shown in fig1 . the diameter build - up device 16 of which only the head is shown in fig1 has split molds 16a , 16a properly incorporated therewith along the periphery of a conical member 16b and are caused to move forward and backward along the axial direction by virtue of hydraulic pressure , and also to expand and reduce in the axial direction on the inclined plane of the conical member 16b . 16b &# 39 ; represent a conical member as is set in place at the position whereto the member 16b moves forward to expand the split mold 16a . the peripheral section 16c of the split mold 16a functions in such a manner as to expand the diameters of the primary and secondary ejection ring sections 14 , 13 . another peripheral section 16d is used for other diameter build - up deformation . in the state shown in fig3 b , the outer peripheral section 14a of the primary ejection ring section 14 causes the thin metal pipe 15a to be subjected to a ring - shaped partial plastic deformation 15d . the clearance x o is changed into a smaller clearance x 1 . the state shown in fig3 c occurs when the primary and secondary ejection ring sections 14 , 13 are concurrently subjected to further diameter build - up , and the connector 10 is fitted in place completely into the pipe connecting end . the partial plastic deformation 15d becomes all the more deeply concave , to thus become a sharp - angled concave groove , and secure mechanical incorporation with the primary ejection ring section 14 is properly attained . the rubber ring 13b , for its part , too , causes the metal pipe 15a to be subjected to gentle plastic deformation outward , to thus produce the same superb sealing force . the sharp - angled partial plastic deformation 15d is superb in sealing function , and is well capable by itself of producing such sealing force as is normally required . the connecting end 15b of the heat insulation pipe has the heat insulation layer 15c kept set intact as a cover over the outer periphery , without being subjected to scaling - off , as shown in the drawing . in case this heat insulation layer is as high in strength as hardened vinyl chloride , pressure adhesion force between the plastic deformation section 15d , 15e and the primary ejection ring section 14 or the rubber ring 13b increases , thus well claimable to have such advantages that not only a troublesome process of stripping of the heat insulation layer is saved but also secure connection can be obtained . shown in fig4 a and fig4 b is a connector 100 which is similar to that shown in fig2 b subject to slight modification , and which is shown in the state thereof prior to , and posterior to , being properly fitted in place , respectively . the flange 110 of the rear section c has a cap nut 111 properly supported thereon . the point thus subjected to modification is that a ring - shaped groove 130a is formed near the boundary between the intermediate section b and the top section a , and a ring - shaped flange 140 formed into the shape of a groove is properly fitted in place with an injection ring 140a of such a diameter as is not in excess of the outer diameter of the intermediate section b . the ejection ring 140a subjects the metal pipe 15a to sharply concaved plastic deformation 15d , and subjects the packing member 130b to gentle plastic deformation 15e , as set forth above ; therefore , such a space which does not result in deformations and which is continuous is properly allowed between the ring - shaped flange 140 and the ring - shaped groove 130a . the said boundary is along the center of this space . in the case of expanding the diameter of the ring - shaped flange 140 by the employment of the diameter build - up tool 16 , the ring - shaped flange 140 can be subjected to sufficiently large a plastic deformation in such a manner that the flexible section constituting the ring - shaped flange is opened ; therefore , the metal pipe 15a can be subjected to plastic deformation at the sufficient height 15d &# 39 ;, even in case the outer diameter of the ejection ring 140a is smaller than the outer diameter of the intermediate section b . as shown in fig4 b showing the state posterior to the diameter build - up treatment , sharp - angled ring - shaped plastic deformation 15d and gentle plastic deformation 15e take shape , whereby both are in pressure contact with the surface of the connector 100 . such other member as the cylinder 113 shown in fig4 b has a nut 112 properly fitted thereon , and , is subjected to diameter build - up by the employment of the diameter build - up tool 16 and by making use of the difference in level 16c &# 39 ; or 16c &# 34 ; between the peripheral section 16c and the peripheral section 16d of the split mold , thus forming a flange 114 in a proper manner . the flange 110 and this flange 114 have a packing member 115 properly held in place between , and the heat insulation pipe is connected with the cylinder 113 in a secure manner by clamping the cap nut 111 and the nut 112 with each other . the sharp - angled ring - shaped side section 15d &# 39 ; of the plastic deformation 15d exhibits a powerful engaging force . when the connector 10 or 100 shown in fig3 a and fig4 a is completely fitted in place into the pipe connecting end , the inner diameter section of the primary ejection ring section 14 and that of the secondary ejection ring section 13 are so kept as to protrude by a bit over the internal peripheral wall of the metal pipe 15a , which , however , has virtually nothing to do with the transfer efficiency of the pipe . likewise , the said state is virtually free from affecting the transfer efficiency , even in case the ring - shaped flange 140 and the ring - shaped concave groove 130 are in the state of slightly protruding over the inner peripheral wall of the pipe 15a . shown in fig5 a is an alternate embodiment wherein a primary ejection ring 14 &# 39 ; has a ring - shaped groove properly formed on the outer peripheral section 14 &# 39 ; a , and a modified connector 100a having a packing member 13 &# 39 ; b properly fitted in place into the ring - shaped groove is inserted into the metal pipe 150 . to put it otherwise , the intermediate section b has no ring - shaped concave section nor a secondary election ring section formed therein . the outer diameter of this intermediate section b is so selected as to be smaller than the inner diameter of the metal pipe 150 , and the rear section c has a flange 11 properly formed therein . shown in fig5 b is such a state wherein the connector 100a therefore is subjected to proper diameter build - up treatment and properly fitted in place by pressure expansion into the connecting end of the metal pipe . the partial ring - shaped plastic deformation 15d of the metal pipe 150 compresses the packing member , and is engaged with the primary ejection ring 14 &# 39 ; in a secure manner , thus producing a mechanically integrated superb connection . this example is a case wherein the connector is applied to a conventional metal pipe having the external side thereof covered with no heat insulation layer at all , as shown in the drawing . therefore , the connecting end of this metal surface has a convex section formed by the plastic deformation 15d and occurring on the outer peripheral surface thereof . shown in fig6 is another alternate embodiment wherein the connector is employed together with a supplementary connector 17 . the connecting end of the pipe has the supplementary connector 17 properly so set in place as to cover the same , then has the connector properly fitted in place after subjecting the same to diameter build - up . thereby the connecting force of the connecting section can be specially enhanced , and the connector produced by the application of the principle of the connection introduced in the present invention can be properly fitted in place for a thin metal film as well , thus resulting in definitely extending the scope of applicability of the connector introduced in the present invention . the material for the supplementary connector 17 include conventional ferrous metal , brass and the like , and hence is unlimited . shown in fig7 is another alternate embodiment showing a supplementary connector 17 &# 39 ; specifically employed for the purpose of the connecting end 15b of the composite pipe 15 which has a covering layer 15c . the inner peripheral wall is the supplementary connector 17 &# 39 ; and has a cylindrical surface , and the outer peripheral wall is properly tapered in such a manner as shown in the drawing , whereby secure fitting between the covering layer 15c and the pipe 15a can be ensured . shown in fig8 a is another alternate connector 100b which is provided with a couple of ejection rings 140a and 140 &# 39 ; a . the groove 140 for receiving the ejection rings is formed at the top section a , and at such a position in the intermediate section b near the rear section c as well . a ring - shaped concave section 130 to set a packing member 130b is properly formed in the space between both rings . as depicted in fig8 b showing the state of being fitted , the sharp - angled ring - shaped plastic deformation 15d is formed in parallel to the double lead pipe 15a ; therefore , even in case such external force as subjects the pipe connecting section to flexure should be applied on the connector 100b , bending moment hardly occurs , to thus display superb stability . fig9 shows another alternate embodiment wherein a connector 100c has bellows 100 &# 39 ; properly formed in the rear section c , and the pipe connecting section is provided with degrees of freedom of the connecting position . this connector 100c has such other advantage that flexural connection can also be conducted thereby , and , in case such external force as subjects the connecting section to flexure and deflection should be applied thereon , such is properly absorbed by the flexibility of the bellows 100 &# 39 ;, and the engaging force making use of sharp - angled plastic deformation is thus properly preserved . the said primary ejection ring section 14 and the ejection ring 140a can be properly subjected to diameter build - up deformation under normal hydraulic pressure by the employment of the diameter build - up tool 16 , even in case the primary ejection ring section and the ejection ring have a complete ring shape . of those , the ejection ring 140a can be used as a split ring ; however , in this case , the construction shown in fig5 a proves to be rather improper , except in the case of employing the packing member 130b infallibly for giving the connector a perfect sealing force . the width of the packing member can be increased readily enough for giving the required sealing force , whenever a specially large sealing force is required . shown in fig1 a through fig1 d are some examples of such a fixing device as join the flange 11 or 110 properly formed for the connector introduced in the present invention . the fitting - fixing tool 118 has a groove for setting a pair of flanges 11 ( or 110 ) therein properly formed in the interior , and a pair of flanges are concurrently fitted in place in combination through the split opening . the packing member can be employed , wherever so required . the fixing tools comprising the cap nut 111 and the nut 112 can likewise be properly combined optionally , prior to fitting the connector 10 , 100 , 100a , 100b , or 100c properly in place on the pipe connecting end , then can be fixed in place at liberty by way of the flange 11 or 110 of the connector . shown in fig1 d is an example wherein fixing devices 116 and 117 of the flange joint type are employed . in case the fixing device 116 has such multiple threads 116a as are shown in fig1 e properly formed on the internal peripheral surface thereof , causing the external peripheral surface of the pipe connecting end to bite in between the said multiple threads at the time of the diameter build - up treatment of the connector 100 not only well serves the fixing device 116 to be properly held in place securely enough , but also for the improvement of the strength of the connecting end , in the same manner as in the case shown in fig6 and fig7 . shown in these drawings is also such a construction wherein a ring flange 110 &# 39 ; is set in place outside the flange 110 . in the case of fitting the ring flange 110 &# 39 ; in place on an object member of connection , the flanges 11 or 110 to be thus jointed with each other are lapped in an accurate manner , and the jointed section is improved in strength at the same time . the fixing device 116 is tied with such other fixing device 117 as is supported by the counterpart flange 110 by the bolt 117a , thus forming secure connection . in case the connector introduced in the present invention has a flange properly formed therefor , various types of fixing devices can be optionally combined , prior to fitting the same on the pipe connecting end , to thus facilitate the use of the fixing devices in an extensive manner , and this constitutes a meritorious feature quite foreign to any conventional connector . the connector of such a type that has a convex thread added on the outer peripheral section 14a of the primary ejection ring section 14 or on the outer peripheral section of the ejection ring 140a is capable of causing this convex thread to bite into the inner peripheral wall of the pipe connecting end . thereby the said convex thread is further caused to bite into the ring - shaped plastic deformation 15d , until the mechanical engagement force and the water - rightness of this section is further improved . furthermore , it is desirable that such an ejection ring section , ring - shaped flange , ring - shaped groove as are to be subjected to diameter build - up ; and the ring - shaped concave section for holding the packing member in place are so formed as to have the same inner diameter , and that the connector is subjected to diameter build - up , in correspondence to the use thereof , so that the diameter build - up treatment can be conducted by a single stage . in the case of designing such a connector as has the section for holding the packing kept free from being subjected to diameter build - up , the thickness of the packing employed is increased by the application of a proper means . the above - mentioned ring - shaped flange and groove for forming the connector are to be shaped by the application of a pressing process including constriction , and the connector as a whole is to be manufactured as a foundary product .