CA1261570A - Method for molding corrugated pipe sleeve - Google Patents
Method for molding corrugated pipe sleeveInfo
- Publication number
- CA1261570A CA1261570A CA000525784A CA525784A CA1261570A CA 1261570 A CA1261570 A CA 1261570A CA 000525784 A CA000525784 A CA 000525784A CA 525784 A CA525784 A CA 525784A CA 1261570 A CA1261570 A CA 1261570A
- Authority
- CA
- Canada
- Prior art keywords
- sleeve
- corrugated pipe
- molding
- ridges
- corrugated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Rigid Pipes And Flexible Pipes (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method or molding a sleeve on a corrugated pipe consisting of an inner wall and fusion-bond ridges.
Two clamps can close to engage several of the ridges. One to three of the ridges project into a molding space between the clamps. A core is inserted into pipe and closes the molding space. Hot pressurized resin softens and collapses the projected ridges and fusion bonds the pipe to the sleeve portion of the molding space.
A method or molding a sleeve on a corrugated pipe consisting of an inner wall and fusion-bond ridges.
Two clamps can close to engage several of the ridges. One to three of the ridges project into a molding space between the clamps. A core is inserted into pipe and closes the molding space. Hot pressurized resin softens and collapses the projected ridges and fusion bonds the pipe to the sleeve portion of the molding space.
Description
~L26~
BACXGROU~D OF THE INVENTION
Field of the Invention This invention relates to a method for molding a connecting plastic sleeve integral with one end of a plastic corrugated drainpipe for use in civil construction work or agriculture, e.g..
3RI F D2S;:~I'TION O~ T~E D~ 3GS
Fig. 1 is a sectional view of a corrugated pipe set in an injection mold.
Fig. 2 is a sectional view of the sleeve-molding space of the injection mold into which molten resin has been injected.
Fig. 3 is an enlarged version of Fig. 2.
Fig. 4 is a sectional view of the corrugated pipe with a sleeve in receipt of another corrugated pipe.
Fig. 5 is a partial sectional view showing the structure of the corrugated pipe.
Fig. 6 is a sectional view showing a conventional method for forming a sleeve.
Fig. 7 is a sectional view showing a conventional method developed by the present inventors for molding a sleeve.
Fig. a is a partial sectional view of the corrugated pipe with the sleeve formed through the method of Fig. 7.
~ 2~5~
~ 2 --1 Bac~qround of the Inventlon A plastic corrugated pipe 1 shown in Fig. 5 is increasingly used as a drainpipe in civil construction work or agriculture. The corrugated pipe 1 is of a double-wall structure and has an outer wall 11 formed of alternate annular ridges 111 and annular grooves 112. An inner wall 12 is fusion-bonded to the grooves 112. Such a corrugated pipe 1 is not only more pressure resistant but is also flexible while relatively light in weight and allows water to smoothly flow therethrough. Due to the above advantages, the corrugated pipe 1 is readily usable as a drainpipe. A variation in which a water passagehole is made in the portion where the inner wall 1~ is fusion-bonded to the groove 112 is particularly recommended as a drainpipe for underdrainage.
Two corrugated pipes are usually connected together using a tube joint. It may sometimes be required, however, to connect two pipes in such a manner as to insert one pipe into a sleeve, which is a receptable integral with an end of the other pipe 1.
When the connecting sleeve is formed at one end oE a conventional cylindrical plastic pipe, the sleeve end is heated to over the softening temperature and sectional dies for forming the sleeve are Eorced into that end to 2s enlarge the diameter. However the above conventional ~IL26:~5~
l method applied to the formation of a sleeve at the end of the corrugated pipe 1, as shown in Fig 6 with a segmental dies 2, presents the following problems. If the end of the corrugated pipe 1 is heated too fast, the air enclosed in between the ridge 111 of the outer wall 11 and the inner wall 12 will be rapidly expanded by heat and the pressure thus developed may damage the ridge 111 or inner wall 12. Moreover, if the end thereof is made too soft by excessive heating or if the sectional dies are expanded too strongly or too fast, the ridge 111 will be deformed or put out of shape. The thus degraded external appearance will reduce its commercial value by a large margin. Particularly, in the case of a corrugated pipe having water passageholes, the external appearance will be deteriorated ~urther because the water passageholes are forced to enlarge and, when the pipe is buried under the ~~ ground, a great deal of earth and sand is allowed to penetrate into the pipe through the water passageholes and the pipe may become clogged with it. ~hen use is made of the conventional method of expanding the diameter at the end of the corrugated pipe 1 to form a sleeve, the end thereof must be treated careEully, that is, it must be heated gently and expanded slowly by the sleeve forming segmental dies. In consequence, it takes at least more than five minutes to form a sleev~. Accordingly, ,h,'',~, ~ 7 1 extremely low forming efficiency and difficultie~ in setting forming conditions have reduced production efficiency.
The present inventors developed a method for molding a sleeve by injection molding as shown in Fig. 7 to solve the above problems and filed an patent application with the Japanese Patent Office (Japanese Patent Application No. 18154/85). The above method comprises preheating and applying pressure to one end la of a corrugated pipe 1 to squash two ridges to form a circular pipe. The circularized pipe end of the corrugated pipe 1 is inserted into a mold 3 equipped with a cavity 31 for molding a sleeve. Molten resin 4a is injected from the resin injection hole 32 into the cavity 31 to mold a sleeve 4, as shown in Fig. 8, which is integral with the end la of the corrugated pipe 1. Since this method requires no process of expanding the diameter of the end of a corrugated pipe as in the case of the conventional one, it offers high forming efficiency and is fit for mass-production because a sleeve can be formed in less then one minute. Notwithstanding, there is still room for improvement from the following standpoints.
In the first place, the end la of the corrugated pipe 1 must be preheated with pressure or cut by a lathe to squash the ridges to form a circular pipe, which results in an increase in the number of production steps.
tl ' ., 7~
1 In ~he second place, the contact between the end la of the corrugated pipe 1 and the outer clamps 33 of the mold 3 is insufficient since the ridges at the end la thereof are squashed to form the circular pipe.
Accordingly, the molten resin may leak out through the small gap between the end la of the corrugated pipe 1 and the outer clamps 33 during the injection of the molten resin. The molten resin thus leaked out forms a flash 41 at the root of the molded sleeve 4, as shown in Fig. 8, thus presenting an ugly appearance. Moreover, the wall thickness of the sleeve 4 is caused to slightly vary because the quantity of the resin being injected into the cavity 31 of the mold 3 for molding the sleeve is not precisely fixed.
Another improvement that should be made is that, since the ridges at the end la of the corrugated pipe 1 are squashed to form the circ~lar pipe, the oute periphery thereof tends to be scarcely caught by the mold 3. Therefore, the end la of the corrugated pipe 1 may be forced back with the pressure applied during the injection of the molten resin. As a result, the sleeve may be molded unsatisfactorily.
Still another improvement that should be made is concerned with the concentration of he3t deformation.
When the sleeve 4 is injection-molded in such a manner as ~..
57~
l to envelop the end la of the corrugated pipe 1, heat deformation tends to be concentrated at the root of the sleeve 4. Consequently, if the end la of the corrugated pipe l is thin, the root of the sleeve 4 is readily broken out on receiving a shock.
SUMMARY OF THE INVENTION
It is thereEore an object of the present invention to provide a method or molding a sleeve with high forming efficiency without the process of squashing the ridges at the end of a corrugated pipe beforehand.
It is another object of the present invention to provide a method for molding a sleeve offering a good exterior appearance without a flash in its root portion and having uniform wall thickness by preventing molten resin from leaking out through the gap between the outer clamp and the end of a corrugated pipe.
I. is still another object of the present invention to provide a method for molding a sleeve free from defects resulting from the forced bac~ end of a corrugated pipe during the in3ection of molten resin.
It is a further object of the present invention to provide a method for molding a sleeve wherein the concentration of heat deformation in its root portion can be relieved.
~26~7~
l The above objects can be achieved by a method for molding a sleeve according to the present invention.
The rnethod comprises the steps of setting the end of a plastic corrugated pipe composed of an outer wall formed of alternate annular ridges and annular grooves and a cylindrical inner wall fusion-bonded to the grooves in such a state that the end thereof has been forced into a sleeve-molding space o an injection mold having the sleeve-molding space between its core and outer clamps.
Molten resin is injected into the sleeve-molding space so as to fusion-soften the end of the corrugated pipe utilizing the resin heat. The ridges are squashed while discharging most of the air confined in between the ridges and the inner wall at the end thereof with the resin pressure out of the sleeve-molding space to fusion-bond the resin to the end thereof.
DETAILED DESCRIPTION OF T~E PREFERRED EMBODIMENTS.
According to the present invention, the end of the corrugated pipe is set in such a ~anner that the end thereof has besn forced into the sleeve-molding space without squashing the ridges at its end. The ridges are squashed by making use oE the heat and pressure of the molten resin injected into the sleeve-moldLng space, f,''';~Y
~ 2~ ~7 ~
1 whereby it becomea entirely unnecessary to preneat and appl~ pressure to the end of the corrugated pipe to squash the ridges prior to setting its end in the injection mold.
The sleeve can thus be molded highly efEi-iently.
A:lthough the present inventors initially expected that such an attempt to mold a sleeve in the sleeve-molding space while squashing the ridges at the end oE the corrugated pipe could be abortive because the air sealed UE) in between the ridges and the inner wall was unable to eccape, they have discovered, however, that the ridges are sauashed completely because the ridges and the inner wall can be actually torn off slightly to allow most of the air to flow into the sleeve-molding space, pass through the small gap between the inner wall and the core and then discharge out of the space. Based on this discovery, they completed the present invention.
Since the ridges at the end of the corrugated pipe are squashed in the sleeve-molding space, the ridges thus s~uashed work to block the gap through which the resin is caused to leak out, i.e., the gap between the outer Eorces and the outer wall oE the corrugated pipe, consequently preventing the resin Erom leaking O~lt oE the sleeve-molding space. The sleeve molded according to method oE the present invention looks better because no Elash is produced in its root portion and, because the ~ 2~ ~ 7 ~
_ g 1 quanti~y o~ molten resin being injected into the sleev2-molding space becomes roughly constant. The wall thic~ness of the sleeve is also prevented from var~ing.
Since the end oE the corrugated pipe is set in the state of being forced into the sleeve-molding space wit:hout squashing its ridges, the corrugated pipe will never be pushed back because the ridges are caught by the front of the sleeve-molding spac~ even though there is applied force toward pushing their corrugated pipe back because of the resin injection pressure.
Since the molten resin is fusion-bonded to the enc of the corrugated pipe to mold the sleeve while the rid.ges are being squashed according to the present invention, heat deformation is hardly concentrated in the root portion of the sleeve but extended to an edge of the ridge remaining as a wall, so that the impact properties of the root portion thereof may seldom be reduced~
Referring now to the accompanying drawings, a preferred embodiment oE the present invention will be ~0 described.
In the method eor molding a sleeve according to the present invention, as shown in Fig 1, one end la of a corrugated pipe 1 is set in such a state that its end is forced into a sleeve-molding space 53 of an injection mold 5 without squashing ridges llla at the end oE the pipe 1.
1 The pl2_'' C cor-uc,~~ed pipe 1 used in this emDadlment is of double-~all structure and has an outer wall 11 formed of alternate annular ridges 111 and annular grooves 112 and a roughly cylindrical inner wall 12 fusion~bonded to the grooves 112. In this case, a water passageholes may further be made in the portion where the inner wall 12 of th~ corrugated pipe is fusion-bonded to the groove 112.
On the other hand, the injection mold 5 is provided with the sleeve-molding space 53 formed bet,ween a core 51 and segmented upper and lower outer clamps 52, 52'. The lower outer clamp 52' is fixed, ~hereas the upper outer clam~ 52 is, movable vertically between the op~!n position shown by a virtual line and the closed poc;ition shown by a continuous line. The core 51 is also mo~able longitudinally between the retreat position shown by a virtual line and the forward position shown by a continuous line. The core 51 is equipped with a head 511 to be fitted into the end la of the corrugated pipe 1.
The upper and lower clamps 52, 52' are provided with corrugated inner surfaces 522 engaging with khe front ridges 111 and grooves 112 on the outer wall 11 oE the corrugated pipe.
The setting of the corrugated pipe in the injectlon mold 5 i5 conducted as follows. The core 51 and
BACXGROU~D OF THE INVENTION
Field of the Invention This invention relates to a method for molding a connecting plastic sleeve integral with one end of a plastic corrugated drainpipe for use in civil construction work or agriculture, e.g..
3RI F D2S;:~I'TION O~ T~E D~ 3GS
Fig. 1 is a sectional view of a corrugated pipe set in an injection mold.
Fig. 2 is a sectional view of the sleeve-molding space of the injection mold into which molten resin has been injected.
Fig. 3 is an enlarged version of Fig. 2.
Fig. 4 is a sectional view of the corrugated pipe with a sleeve in receipt of another corrugated pipe.
Fig. 5 is a partial sectional view showing the structure of the corrugated pipe.
Fig. 6 is a sectional view showing a conventional method for forming a sleeve.
Fig. 7 is a sectional view showing a conventional method developed by the present inventors for molding a sleeve.
Fig. a is a partial sectional view of the corrugated pipe with the sleeve formed through the method of Fig. 7.
~ 2~5~
~ 2 --1 Bac~qround of the Inventlon A plastic corrugated pipe 1 shown in Fig. 5 is increasingly used as a drainpipe in civil construction work or agriculture. The corrugated pipe 1 is of a double-wall structure and has an outer wall 11 formed of alternate annular ridges 111 and annular grooves 112. An inner wall 12 is fusion-bonded to the grooves 112. Such a corrugated pipe 1 is not only more pressure resistant but is also flexible while relatively light in weight and allows water to smoothly flow therethrough. Due to the above advantages, the corrugated pipe 1 is readily usable as a drainpipe. A variation in which a water passagehole is made in the portion where the inner wall 1~ is fusion-bonded to the groove 112 is particularly recommended as a drainpipe for underdrainage.
Two corrugated pipes are usually connected together using a tube joint. It may sometimes be required, however, to connect two pipes in such a manner as to insert one pipe into a sleeve, which is a receptable integral with an end of the other pipe 1.
When the connecting sleeve is formed at one end oE a conventional cylindrical plastic pipe, the sleeve end is heated to over the softening temperature and sectional dies for forming the sleeve are Eorced into that end to 2s enlarge the diameter. However the above conventional ~IL26:~5~
l method applied to the formation of a sleeve at the end of the corrugated pipe 1, as shown in Fig 6 with a segmental dies 2, presents the following problems. If the end of the corrugated pipe 1 is heated too fast, the air enclosed in between the ridge 111 of the outer wall 11 and the inner wall 12 will be rapidly expanded by heat and the pressure thus developed may damage the ridge 111 or inner wall 12. Moreover, if the end thereof is made too soft by excessive heating or if the sectional dies are expanded too strongly or too fast, the ridge 111 will be deformed or put out of shape. The thus degraded external appearance will reduce its commercial value by a large margin. Particularly, in the case of a corrugated pipe having water passageholes, the external appearance will be deteriorated ~urther because the water passageholes are forced to enlarge and, when the pipe is buried under the ~~ ground, a great deal of earth and sand is allowed to penetrate into the pipe through the water passageholes and the pipe may become clogged with it. ~hen use is made of the conventional method of expanding the diameter at the end of the corrugated pipe 1 to form a sleeve, the end thereof must be treated careEully, that is, it must be heated gently and expanded slowly by the sleeve forming segmental dies. In consequence, it takes at least more than five minutes to form a sleev~. Accordingly, ,h,'',~, ~ 7 1 extremely low forming efficiency and difficultie~ in setting forming conditions have reduced production efficiency.
The present inventors developed a method for molding a sleeve by injection molding as shown in Fig. 7 to solve the above problems and filed an patent application with the Japanese Patent Office (Japanese Patent Application No. 18154/85). The above method comprises preheating and applying pressure to one end la of a corrugated pipe 1 to squash two ridges to form a circular pipe. The circularized pipe end of the corrugated pipe 1 is inserted into a mold 3 equipped with a cavity 31 for molding a sleeve. Molten resin 4a is injected from the resin injection hole 32 into the cavity 31 to mold a sleeve 4, as shown in Fig. 8, which is integral with the end la of the corrugated pipe 1. Since this method requires no process of expanding the diameter of the end of a corrugated pipe as in the case of the conventional one, it offers high forming efficiency and is fit for mass-production because a sleeve can be formed in less then one minute. Notwithstanding, there is still room for improvement from the following standpoints.
In the first place, the end la of the corrugated pipe 1 must be preheated with pressure or cut by a lathe to squash the ridges to form a circular pipe, which results in an increase in the number of production steps.
tl ' ., 7~
1 In ~he second place, the contact between the end la of the corrugated pipe 1 and the outer clamps 33 of the mold 3 is insufficient since the ridges at the end la thereof are squashed to form the circular pipe.
Accordingly, the molten resin may leak out through the small gap between the end la of the corrugated pipe 1 and the outer clamps 33 during the injection of the molten resin. The molten resin thus leaked out forms a flash 41 at the root of the molded sleeve 4, as shown in Fig. 8, thus presenting an ugly appearance. Moreover, the wall thickness of the sleeve 4 is caused to slightly vary because the quantity of the resin being injected into the cavity 31 of the mold 3 for molding the sleeve is not precisely fixed.
Another improvement that should be made is that, since the ridges at the end la of the corrugated pipe 1 are squashed to form the circ~lar pipe, the oute periphery thereof tends to be scarcely caught by the mold 3. Therefore, the end la of the corrugated pipe 1 may be forced back with the pressure applied during the injection of the molten resin. As a result, the sleeve may be molded unsatisfactorily.
Still another improvement that should be made is concerned with the concentration of he3t deformation.
When the sleeve 4 is injection-molded in such a manner as ~..
57~
l to envelop the end la of the corrugated pipe 1, heat deformation tends to be concentrated at the root of the sleeve 4. Consequently, if the end la of the corrugated pipe l is thin, the root of the sleeve 4 is readily broken out on receiving a shock.
SUMMARY OF THE INVENTION
It is thereEore an object of the present invention to provide a method or molding a sleeve with high forming efficiency without the process of squashing the ridges at the end of a corrugated pipe beforehand.
It is another object of the present invention to provide a method for molding a sleeve offering a good exterior appearance without a flash in its root portion and having uniform wall thickness by preventing molten resin from leaking out through the gap between the outer clamp and the end of a corrugated pipe.
I. is still another object of the present invention to provide a method for molding a sleeve free from defects resulting from the forced bac~ end of a corrugated pipe during the in3ection of molten resin.
It is a further object of the present invention to provide a method for molding a sleeve wherein the concentration of heat deformation in its root portion can be relieved.
~26~7~
l The above objects can be achieved by a method for molding a sleeve according to the present invention.
The rnethod comprises the steps of setting the end of a plastic corrugated pipe composed of an outer wall formed of alternate annular ridges and annular grooves and a cylindrical inner wall fusion-bonded to the grooves in such a state that the end thereof has been forced into a sleeve-molding space o an injection mold having the sleeve-molding space between its core and outer clamps.
Molten resin is injected into the sleeve-molding space so as to fusion-soften the end of the corrugated pipe utilizing the resin heat. The ridges are squashed while discharging most of the air confined in between the ridges and the inner wall at the end thereof with the resin pressure out of the sleeve-molding space to fusion-bond the resin to the end thereof.
DETAILED DESCRIPTION OF T~E PREFERRED EMBODIMENTS.
According to the present invention, the end of the corrugated pipe is set in such a ~anner that the end thereof has besn forced into the sleeve-molding space without squashing the ridges at its end. The ridges are squashed by making use oE the heat and pressure of the molten resin injected into the sleeve-moldLng space, f,''';~Y
~ 2~ ~7 ~
1 whereby it becomea entirely unnecessary to preneat and appl~ pressure to the end of the corrugated pipe to squash the ridges prior to setting its end in the injection mold.
The sleeve can thus be molded highly efEi-iently.
A:lthough the present inventors initially expected that such an attempt to mold a sleeve in the sleeve-molding space while squashing the ridges at the end oE the corrugated pipe could be abortive because the air sealed UE) in between the ridges and the inner wall was unable to eccape, they have discovered, however, that the ridges are sauashed completely because the ridges and the inner wall can be actually torn off slightly to allow most of the air to flow into the sleeve-molding space, pass through the small gap between the inner wall and the core and then discharge out of the space. Based on this discovery, they completed the present invention.
Since the ridges at the end of the corrugated pipe are squashed in the sleeve-molding space, the ridges thus s~uashed work to block the gap through which the resin is caused to leak out, i.e., the gap between the outer Eorces and the outer wall oE the corrugated pipe, consequently preventing the resin Erom leaking O~lt oE the sleeve-molding space. The sleeve molded according to method oE the present invention looks better because no Elash is produced in its root portion and, because the ~ 2~ ~ 7 ~
_ g 1 quanti~y o~ molten resin being injected into the sleev2-molding space becomes roughly constant. The wall thic~ness of the sleeve is also prevented from var~ing.
Since the end oE the corrugated pipe is set in the state of being forced into the sleeve-molding space wit:hout squashing its ridges, the corrugated pipe will never be pushed back because the ridges are caught by the front of the sleeve-molding spac~ even though there is applied force toward pushing their corrugated pipe back because of the resin injection pressure.
Since the molten resin is fusion-bonded to the enc of the corrugated pipe to mold the sleeve while the rid.ges are being squashed according to the present invention, heat deformation is hardly concentrated in the root portion of the sleeve but extended to an edge of the ridge remaining as a wall, so that the impact properties of the root portion thereof may seldom be reduced~
Referring now to the accompanying drawings, a preferred embodiment oE the present invention will be ~0 described.
In the method eor molding a sleeve according to the present invention, as shown in Fig 1, one end la of a corrugated pipe 1 is set in such a state that its end is forced into a sleeve-molding space 53 of an injection mold 5 without squashing ridges llla at the end oE the pipe 1.
1 The pl2_'' C cor-uc,~~ed pipe 1 used in this emDadlment is of double-~all structure and has an outer wall 11 formed of alternate annular ridges 111 and annular grooves 112 and a roughly cylindrical inner wall 12 fusion~bonded to the grooves 112. In this case, a water passageholes may further be made in the portion where the inner wall 12 of th~ corrugated pipe is fusion-bonded to the groove 112.
On the other hand, the injection mold 5 is provided with the sleeve-molding space 53 formed bet,ween a core 51 and segmented upper and lower outer clamps 52, 52'. The lower outer clamp 52' is fixed, ~hereas the upper outer clam~ 52 is, movable vertically between the op~!n position shown by a virtual line and the closed poc;ition shown by a continuous line. The core 51 is also mo~able longitudinally between the retreat position shown by a virtual line and the forward position shown by a continuous line. The core 51 is equipped with a head 511 to be fitted into the end la of the corrugated pipe 1.
The upper and lower clamps 52, 52' are provided with corrugated inner surfaces 522 engaging with khe front ridges 111 and grooves 112 on the outer wall 11 oE the corrugated pipe.
The setting of the corrugated pipe in the injectlon mold 5 i5 conducted as follows. The core 51 and
2~ the upper outer clamp 52 are respectively moved to the back and open positions beforehand and the corrugated pipe ~ 7 ~
1 1 ia -,:cun,-d on the lo~er outer cl amD ~2 ' so .ha~ its t~o riasea llla at the end la thereof are ~orced into the slee~e-~olding space 5. Then, the ridges 111 and grooves 112 are made to engage with the corrugated inner surface 522. Subsequently, the core 51 is moved forward to fit its head 511 into the end ?a of the corrugated pipe 1. As the front of the head 511 i5 tapered, the head 511 can easily be fi-tted therein even if th;e position or direction of the corrugated pipe 1 is slightly shifted. The corrugated pipe 1 is fixed in position and direction when it is thu~ fitted until its root of the head 511 abuts against the end la of the pipe 1. The upper outer clamp 5~ is lastly lowered and its corrugated inner surface 522 is made to engage with the ridges 111 and grooves 112 of the corrugated pipe 1 to envelope and fix the portion close to the end of the corrugated pipe 1. While the corrugated pipe 1 is thus set, the side of the second rid~e llla from the end la of the corrugated pipe 1 abuts against the front dividing face 521 oE the sleeve-molding ZO space of the outer clamps 52, 52'.
Since the corrugated inner sur~aces 522 of the upper and lower outer clamps 52, 52' are engaged with the ridges 111 and grooves 112 to énvelope and fix the portion clo~e to the end of the corrugated pipe 1, the corrugated pipe 1 can be set firmly and steadily. Consequently~ when ~2~7 thC ~o~ n resin is inJe~__s l'r.~_ t:~- sl_^-~2-~olding space 53 as described hereinafter, the corrugated pipe l is never pusne~ back by the pressure ap?lied. To envelop and firmly fix the corrugated pipe l, it is preferred to set the nurnber of ridges lll engaging with the rugged surfaces S22 of the outer clarnps 52, 52' within the range of 2 -10. Six ridges lll are made to engage with the rugged surfaces 522 in this embodiment. If one ridge lll is engaged therewith, the corrugated pipe l may be fixed unsatisfactorily~ whereas the:outer clamps 52, 52' will become unnecessarily large if more than lO ridges are thus engaged. Either of the above cases is therefore not pr~!ferred.
When the corrugated pipe 1 is thus set, as shown in Fig. 2, the molten resin 6a is injected from the in~ection hole 54 into the sleeve molding space 5. Since the molten resin 6a is thus injected, the end la of the corrugated pipe l is softened and fused by the heat o the resin 6a and the two ridges llla at the end la of the corrugated pipe 1 are squashed by the pressure oE the heated resin 6a so that the resin 6a .is Eusion-bonded to the end la of the corrugated pipe 1 to form tha sleeve 6 integral with the pipe 1. Mos-t of the air confined in between the ridges llla and the inner wall 12 is caused to flow into ~he sleeve-mol.ding space 53 through a crack ~6~i7~3 1 produced in the riage llla an~ the inner wall 12. ~he e r is further discharged out o, the sleeve-~olding space 53 through the small gap bet-~een the inner wall 12 and the core 51. Thereby the two front ridges llla are almost completely squashed.
Fig~ 3 shows typical profiles of the squashed ridges llla. More specifically, the endmost ridge llla at the end la of the corrugated pipe~l has been de~ormed in the direction of the injected molten resin 6a and bent on itself with a small space left between itself and the inner wall 12. On the contrary, the second ridge llla frcm the end la of the corrugated pipe 1 has been pressed against the front dividing face 521 of the sleeve-molding spa.ce and bent on itself and, because it receives the pressure OL the molten resin 6a directly, there is no spz.ce left between itself and the inner wall 12. Since th~ second ridge llla from the end thereof is pressed against the front dividing face 521 and thus squashed, the second ridge llla works to check the leakage of the molte~
resin 6a. In consequence, no flash is produced at the root oE the sleeve 6, whereby the sleeve 6 having a good external appearance is eormed. Moreover, the corrugated pipe 1 is never pushed back because Oe the pressure oE the resin 6a since the second ridge llla is caught b~ the front dividing face 521. Since the molten resin. 6a is 57~
1 fus~on-~ondQd to the end la of ~he corrugated plpe 1 .o form the sleeve while the ridges llla at the end la o~ the corrllgated pipe 1 are squashed as shown in Fig 3, heat deformation is decentralized over the squashed ridges llla and not concentrated at the root oE the sleeve 6. As a result, there is little fear for reduction in shock reC.istance at the root of the slee-le 6.
As the molten resin 6a, use can be made of what is compatible with the material resin of the corrugated piE~e 1, e.g., polyethylene, high-density polyethylene, pol.yvinyl chloride, polypropylene and the like. Of the abcve materials, the high-density polyethylene is most suitable because it is less expensive but offers excellent formability and high strength. In addition, it is generally used as the material resin of the corrugated piEe 1. The temperature and pressure immediately before the injection of the molten resin 6a are dependent on the kind of resin and the size of the corrugated pipe 1 and may be determined according to the kind and the size khereof. When the sleeve 6 is molded using high-density polyethylene as the molten resin 6a at the end oE a corrugated pipe of high-density polyethylene having a diameter of 100 mm and inner and outer wall thiclcnesses range from 0.~ - 1.5 mm, it is preferred to set the resin temperature to 180 - 230C, the injection pressure at a ~ ~6 ~7 ~
1 naximum OL 120 ks-/cm2 or 1O~Qr~ ~e adoption or these temperature and pressure conditions makes it possible to he~t the end la of the corrugated piFe 1 at over 135C to sufficiently soften and fuse its end, almost completely squash the end ridges llla and allow the molten resin 6a ~o be firmly usion-bonded to its end.
Although two ridges llla at the end la of the cc1rrugated pipe 1 are to be squashed in this embodiment, at: least one of the ridges llla or three ridges at a maximum should be squashed. If more than three ridges are to be squashed, all the ridges llla are not easily squashed and the quantity of molten resin to be injected increases, i.e., it is uneconomical.
Obviously according to the present invention, a sleeve can be formed efficiently at the end of not only a small corrugated pipe whose diameter is about 50 mm and inner and outer wall thicknesses range from 0.3 to 1.2 mm but also a large one whose diameter is about 400 mm ~nd inner and outer wall thicknesses range from 1.0 to 4.0 mm.
Particularly when a sleeve is formed at the end oE a large corrugated pipe, it is preferred to smooth the air discharge at the time of injection molding by boring an air vent in the ridge to be squashed or inner wall at the end of the corrugated pipe to ensure that the ridge is readily squashed.
i7~
1 The corrugatcd pipe 1 equipped with a siecve integral with one end thereof accordi~g to the present invention is e~tremel~ convenient in that, as shown in Fig. 4, another corrugated pipe 1' can readily be coupled thereto by inserting the end of the second pipe 1' into the sleeve 6. As set forth above, moreover, the exterior appearance of the sleeve 6, particularly the portion at its root is excellent and the shock resistance of the root portion is satisfactory, so that such a corrugated pipe is of high ccmmercial value. When two corrugated pipes are c~upled in the above state, the force applied in the direction in which the diameter of the sleeve 6 is expanded tends to gather and, if the diameter of the sleeve is expanded thereby, the corrugated pipe 1' may easily slip off the sleeve 6, thus causing water leakage.
In order to prevent such leakage, it is pre~erred to pr~vide, as shown in Fig~ 1, a plurality of rib for~ning grooves 523 in the outer clamps 52, 52' to form a plurality of annular reinEorcing ribs 61 (Fig. 4) on the sleeve 6. An O~ring 7 is fitted in the groove at the end oE the corrugated pipe 1' to be plugged.
1 1 ia -,:cun,-d on the lo~er outer cl amD ~2 ' so .ha~ its t~o riasea llla at the end la thereof are ~orced into the slee~e-~olding space 5. Then, the ridges 111 and grooves 112 are made to engage with the corrugated inner surface 522. Subsequently, the core 51 is moved forward to fit its head 511 into the end ?a of the corrugated pipe 1. As the front of the head 511 i5 tapered, the head 511 can easily be fi-tted therein even if th;e position or direction of the corrugated pipe 1 is slightly shifted. The corrugated pipe 1 is fixed in position and direction when it is thu~ fitted until its root of the head 511 abuts against the end la of the pipe 1. The upper outer clamp 5~ is lastly lowered and its corrugated inner surface 522 is made to engage with the ridges 111 and grooves 112 of the corrugated pipe 1 to envelope and fix the portion close to the end of the corrugated pipe 1. While the corrugated pipe 1 is thus set, the side of the second rid~e llla from the end la of the corrugated pipe 1 abuts against the front dividing face 521 oE the sleeve-molding ZO space of the outer clamps 52, 52'.
Since the corrugated inner sur~aces 522 of the upper and lower outer clamps 52, 52' are engaged with the ridges 111 and grooves 112 to énvelope and fix the portion clo~e to the end of the corrugated pipe 1, the corrugated pipe 1 can be set firmly and steadily. Consequently~ when ~2~7 thC ~o~ n resin is inJe~__s l'r.~_ t:~- sl_^-~2-~olding space 53 as described hereinafter, the corrugated pipe l is never pusne~ back by the pressure ap?lied. To envelop and firmly fix the corrugated pipe l, it is preferred to set the nurnber of ridges lll engaging with the rugged surfaces S22 of the outer clarnps 52, 52' within the range of 2 -10. Six ridges lll are made to engage with the rugged surfaces 522 in this embodiment. If one ridge lll is engaged therewith, the corrugated pipe l may be fixed unsatisfactorily~ whereas the:outer clamps 52, 52' will become unnecessarily large if more than lO ridges are thus engaged. Either of the above cases is therefore not pr~!ferred.
When the corrugated pipe 1 is thus set, as shown in Fig. 2, the molten resin 6a is injected from the in~ection hole 54 into the sleeve molding space 5. Since the molten resin 6a is thus injected, the end la of the corrugated pipe l is softened and fused by the heat o the resin 6a and the two ridges llla at the end la of the corrugated pipe 1 are squashed by the pressure oE the heated resin 6a so that the resin 6a .is Eusion-bonded to the end la of the corrugated pipe 1 to form tha sleeve 6 integral with the pipe 1. Mos-t of the air confined in between the ridges llla and the inner wall 12 is caused to flow into ~he sleeve-mol.ding space 53 through a crack ~6~i7~3 1 produced in the riage llla an~ the inner wall 12. ~he e r is further discharged out o, the sleeve-~olding space 53 through the small gap bet-~een the inner wall 12 and the core 51. Thereby the two front ridges llla are almost completely squashed.
Fig~ 3 shows typical profiles of the squashed ridges llla. More specifically, the endmost ridge llla at the end la of the corrugated pipe~l has been de~ormed in the direction of the injected molten resin 6a and bent on itself with a small space left between itself and the inner wall 12. On the contrary, the second ridge llla frcm the end la of the corrugated pipe 1 has been pressed against the front dividing face 521 of the sleeve-molding spa.ce and bent on itself and, because it receives the pressure OL the molten resin 6a directly, there is no spz.ce left between itself and the inner wall 12. Since th~ second ridge llla from the end thereof is pressed against the front dividing face 521 and thus squashed, the second ridge llla works to check the leakage of the molte~
resin 6a. In consequence, no flash is produced at the root oE the sleeve 6, whereby the sleeve 6 having a good external appearance is eormed. Moreover, the corrugated pipe 1 is never pushed back because Oe the pressure oE the resin 6a since the second ridge llla is caught b~ the front dividing face 521. Since the molten resin. 6a is 57~
1 fus~on-~ondQd to the end la of ~he corrugated plpe 1 .o form the sleeve while the ridges llla at the end la o~ the corrllgated pipe 1 are squashed as shown in Fig 3, heat deformation is decentralized over the squashed ridges llla and not concentrated at the root oE the sleeve 6. As a result, there is little fear for reduction in shock reC.istance at the root of the slee-le 6.
As the molten resin 6a, use can be made of what is compatible with the material resin of the corrugated piE~e 1, e.g., polyethylene, high-density polyethylene, pol.yvinyl chloride, polypropylene and the like. Of the abcve materials, the high-density polyethylene is most suitable because it is less expensive but offers excellent formability and high strength. In addition, it is generally used as the material resin of the corrugated piEe 1. The temperature and pressure immediately before the injection of the molten resin 6a are dependent on the kind of resin and the size of the corrugated pipe 1 and may be determined according to the kind and the size khereof. When the sleeve 6 is molded using high-density polyethylene as the molten resin 6a at the end oE a corrugated pipe of high-density polyethylene having a diameter of 100 mm and inner and outer wall thiclcnesses range from 0.~ - 1.5 mm, it is preferred to set the resin temperature to 180 - 230C, the injection pressure at a ~ ~6 ~7 ~
1 naximum OL 120 ks-/cm2 or 1O~Qr~ ~e adoption or these temperature and pressure conditions makes it possible to he~t the end la of the corrugated piFe 1 at over 135C to sufficiently soften and fuse its end, almost completely squash the end ridges llla and allow the molten resin 6a ~o be firmly usion-bonded to its end.
Although two ridges llla at the end la of the cc1rrugated pipe 1 are to be squashed in this embodiment, at: least one of the ridges llla or three ridges at a maximum should be squashed. If more than three ridges are to be squashed, all the ridges llla are not easily squashed and the quantity of molten resin to be injected increases, i.e., it is uneconomical.
Obviously according to the present invention, a sleeve can be formed efficiently at the end of not only a small corrugated pipe whose diameter is about 50 mm and inner and outer wall thicknesses range from 0.3 to 1.2 mm but also a large one whose diameter is about 400 mm ~nd inner and outer wall thicknesses range from 1.0 to 4.0 mm.
Particularly when a sleeve is formed at the end oE a large corrugated pipe, it is preferred to smooth the air discharge at the time of injection molding by boring an air vent in the ridge to be squashed or inner wall at the end of the corrugated pipe to ensure that the ridge is readily squashed.
i7~
1 The corrugatcd pipe 1 equipped with a siecve integral with one end thereof accordi~g to the present invention is e~tremel~ convenient in that, as shown in Fig. 4, another corrugated pipe 1' can readily be coupled thereto by inserting the end of the second pipe 1' into the sleeve 6. As set forth above, moreover, the exterior appearance of the sleeve 6, particularly the portion at its root is excellent and the shock resistance of the root portion is satisfactory, so that such a corrugated pipe is of high ccmmercial value. When two corrugated pipes are c~upled in the above state, the force applied in the direction in which the diameter of the sleeve 6 is expanded tends to gather and, if the diameter of the sleeve is expanded thereby, the corrugated pipe 1' may easily slip off the sleeve 6, thus causing water leakage.
In order to prevent such leakage, it is pre~erred to pr~vide, as shown in Fig~ 1, a plurality of rib for~ning grooves 523 in the outer clamps 52, 52' to form a plurality of annular reinEorcing ribs 61 (Fig. 4) on the sleeve 6. An O~ring 7 is fitted in the groove at the end oE the corrugated pipe 1' to be plugged.
Claims (13)
1. A method for molding a sleeve on a corrugated pipe comprising the steps of:
setting an end of a plastic corrugated pipe into a cavity of an injection mold defined between a core and outer mold clamps and closing said injection mold to define a sleeve-molding space between the end of said corrugated pipe positioned on said core and said outer mold clamps, said pipe end comprising a outer wall formed of alternate annular ridges and annular grooves and a cylindrical inner wall fusion bonded to said grooves; and forming said sleeve by injecting molten resin into said sleeve-molding space so as to fusion-soften the end of said corrugated pipe utilizing a heat of said molten resin, to squash the ridges while discharging most of the air confined in between the ridges and the inner wall at the end thereof out of said sleeve-molding space with the resin pressure and to fusion-bond the resin forming said sleeve to said pipe end including said squashed ridges.
2. A method for molding a sleeve on a corrugated pipe as claimed in claim 1, wherein said outer mold clamps define front dividing faces of said sleeve-molding space and said
setting an end of a plastic corrugated pipe into a cavity of an injection mold defined between a core and outer mold clamps and closing said injection mold to define a sleeve-molding space between the end of said corrugated pipe positioned on said core and said outer mold clamps, said pipe end comprising a outer wall formed of alternate annular ridges and annular grooves and a cylindrical inner wall fusion bonded to said grooves; and forming said sleeve by injecting molten resin into said sleeve-molding space so as to fusion-soften the end of said corrugated pipe utilizing a heat of said molten resin, to squash the ridges while discharging most of the air confined in between the ridges and the inner wall at the end thereof out of said sleeve-molding space with the resin pressure and to fusion-bond the resin forming said sleeve to said pipe end including said squashed ridges.
2. A method for molding a sleeve on a corrugated pipe as claimed in claim 1, wherein said outer mold clamps define front dividing faces of said sleeve-molding space and said
Claim 2 continued....
corrugated pipe is set in such a state that the side of one ridge at the end of said pipe is abutting against said front dividing faces.
corrugated pipe is set in such a state that the side of one ridge at the end of said pipe is abutting against said front dividing faces.
3. A method for molding a sleeve on a corrugated pipe as claimed in claim 2, wherein said outer mold clamps have inner corrugated surfaces in a direction of said front dividing faces away from said sleeve-molding space, said inner corrugated surfaces engaging with the ridges and grooves on the outer wall of said corrugated pipe and wherein said corrugated pipe is set in such a state that the portion close to the end of said corrugated pipe is enveloped and fixed by said inner corrugated surfaces.
4. A method for molding a sleeve on a corrugated pipe as claimed in claim 1, wherein the number of ridges at the end of said corrugated pipe set into said sleeve-molding space is 1-3.
5. A method for molding a sleeve on a corrugated pipe as claimed in claim 2, wherein the number of ridges at the end of said corrugated pipe set into said sleeve-molding space is 1-3.
6. A method for molding a sleeve on a corrugated pipe as claimed in claim 3, wherein the number of ridges at the end of said corrugated pipe set into said sleeve-molding space is 1-3.
7. A method for molding a sleeve on a corrugated pipe as claimed in claim 3, wherein the number of ridges on the outer wall of said corrugated pipe which engage with the corrugated surfaces of said outer mold clamps is 2-10.
8. A method for molding a sleeve on a corrugated pipe as claimed in claim 3, wherein said outer mold clamps are vertically divided segmental clamps and wherein said setting step comprises:
mounting said corrugated pipe on a lower one of said clamps;
engaging the ridges and grooves of said corrugated pipe with the inner surface of the lower clamp, moving and fitting the core in the end of said corrugated pipe;
lowering an upper one of said clamps, thereby engaging the ridges and grooves of said corrugated pipe with the inner corrugated surface of the upper clamp.
mounting said corrugated pipe on a lower one of said clamps;
engaging the ridges and grooves of said corrugated pipe with the inner surface of the lower clamp, moving and fitting the core in the end of said corrugated pipe;
lowering an upper one of said clamps, thereby engaging the ridges and grooves of said corrugated pipe with the inner corrugated surface of the upper clamp.
9. A method for molding a sleeve on a corrugated pipe as claimed in claim 1, further comprising boring an air vent in a ridge or an inner wall at the end of said corrugated pipe set into said sleeve-molding space beforehand.
10. A method for molding a sleeve on a corrugated pipe as claimed in claim 1, wherein said molten resin is high-density polyethylene.
11. A method for molding a sleeve on a corrugated pipe as claimed in claim 10, wherein the temperature of the high-density polyethylene immediately before being injected is set at 180-230°C., whereas the injection pressure thereof is set at maximum of 120 kgf/cm2.
12. A method for molding a sleeve on a corrugated pipe as claimed in claim 1, wherein said sleeve-molding space includes a sleeve portion extending away from the end of said corrugated pipe and having an inner diameter larger than an outer diameter of said inner wall of said corrugated pipe.
13. A method for molding a sleeve on a corrugated pipe as claimed in claim 12, wherein said sleeve-molding space further comprises at least one circumferential outwardly extending rib-forming groove.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000525784A CA1261570A (en) | 1986-12-18 | 1986-12-18 | Method for molding corrugated pipe sleeve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000525784A CA1261570A (en) | 1986-12-18 | 1986-12-18 | Method for molding corrugated pipe sleeve |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1261570A true CA1261570A (en) | 1989-09-26 |
Family
ID=4134588
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000525784A Expired CA1261570A (en) | 1986-12-18 | 1986-12-18 | Method for molding corrugated pipe sleeve |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1261570A (en) |
-
1986
- 1986-12-18 CA CA000525784A patent/CA1261570A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4724111A (en) | Method for molding corrugated pipe sleeve | |
| CA2614587C (en) | Pipe connection | |
| US8579334B2 (en) | Pipe with integral male and female ends, a joint made using the same pipe, and processes of making the pipe and the joint | |
| US6998588B2 (en) | Heat fusion fitting | |
| US5057263A (en) | Method of forming a pipe socket | |
| EP0052017B1 (en) | Channelled plastic pipe with channel ends closed and method of producing the same | |
| KR930009045B1 (en) | Method of producing lined humepipe | |
| CA1261570A (en) | Method for molding corrugated pipe sleeve | |
| US4345956A (en) | Method for making a pipe connection or fitting | |
| JPS62116119A (en) | Molding process for sleeve of corrugated tube | |
| EP0001482A1 (en) | Thermoplastics pipes provided with integral sockets and/or spigots | |
| EP1108179B1 (en) | Casing with provision for closing an opening therein | |
| JP5034603B2 (en) | Manufacturing method of in-core for joint | |
| KR940009885B1 (en) | Sleeve forming method for pipe | |
| JPH07171908A (en) | Production of flanged resin lining steel pipe | |
| JPH0477191B2 (en) | ||
| JPH08216262A (en) | Connecting method for synthetic resin tube to tube joint | |
| JPS6335980Y2 (en) | ||
| EP0094730B1 (en) | A plastic pipe and method for manufacturing a plastic pipe of this type | |
| JP3112344B2 (en) | Forming method of tube spout | |
| JPS6039238Y2 (en) | resin pipe fittings | |
| JP3569565B2 (en) | Electric fusion joint | |
| JPS6157519B2 (en) | ||
| CN101336154A (en) | Method of making a composite product | |
| JPS5976210A (en) | Socket structure of synthetic resin pipe and forming method for socket |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |