CA2182132A1 - Continuous casting of a two-wall corrugated plastic pipe with integral joining means - Google Patents
Continuous casting of a two-wall corrugated plastic pipe with integral joining meansInfo
- Publication number
- CA2182132A1 CA2182132A1 CA002182132A CA2182132A CA2182132A1 CA 2182132 A1 CA2182132 A1 CA 2182132A1 CA 002182132 A CA002182132 A CA 002182132A CA 2182132 A CA2182132 A CA 2182132A CA 2182132 A1 CA2182132 A1 CA 2182132A1
- Authority
- CA
- Canada
- Prior art keywords
- pipe
- wall
- bell
- severing
- region
- 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.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/13—Articles with a cross-section varying in the longitudinal direction, e.g. corrugated pipes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/12—Articles with an irregular circumference when viewed in cross-section, e.g. window profiles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
- B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C57/00—Shaping of tube ends, e.g. flanging, belling or closing; Apparatus therefor, e.g. collapsible mandrels
- B29C57/02—Belling or enlarging, e.g. combined with forming a groove
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
Abstract
A method and apparatus extrudes a two-walled plastic pipe with inner and outer walls and an integral joining means and forms the inner wall as a continuous cylindrical sleeve that is bonded to the inner portion of the outer wall. When the outer wall is formed as a cylindrical corrugation, the inner ribs merge with the outer diameter of the inner wall and periodically during the continuous casting a mold section of greater diameter defines a bell region which ultimately becomes the joining means between two lengths of pipe though continuously manufactured according to the invention by a travelling tunnel mold. The pipe, after molding, is severed at the bell section and the lead portion of the bell section is severed away and the inner wall of the bell portion is also cut away so that an integral bell to a fixed length of corrugated two-walled pipe is formed.
Description
2i8~32 CONTINUOUS CASTING OF A TWO-WALL
CORRUGATED PLASTIC PIPE WITH
INTEGRAL JOINING MEANS
This invention relates to continuously extruding or casting of a two-wall corrugated plastic pipe so as to provide a pipe with a smooth internal bore and an integrally molded outer corrugated profile and as well, an integrally molded joining means.
BACKGROUND TO THE INVENTION
The fabrication of single wall corrugated pipe has been known for a number of years. Because of the corrugated inner diameter inherent turbulence of waterflow through the pipe occurs which requires the pipe diameter to be significantly increased in order to allow a given waterflow to occur. It has been recognized that a smooth internal bore pipe could be made of smaller diameter, hence, reduced resin requirement, cost and weight. Corrugations have an advantage in that they add strength to the fabricated pipe and reduce the wall thickness of material used.
LUPKE, in Canadian Patent No. 2,089,183 issued 15 December, 1992, discloses a TRAVELLING MOLD TUNNEL
APPARATUS FOR SMOOTH WALLED PIPE. Particularly the pipe is provided with a smooth inner bore and with an outer corrugated surface, but it is a single wall pipe formed by a travelling mold tunnel and the utilization of a thermal plastic extrusion nozzle to provide a cylindrical or tubular parison into the travelling mold tunnel. A mandrel expands the internal diameter of the parison and urges it against the corrugated inner diameter of the travelling mold to form an outer corrugated surface and a smooth inner bore for the extruded pipe. Additionally, there is provided, periodically, in the travelling mold block chain, one or more adjacent blocks which have a larger inner diameter. The mandrel is provided with a cooling plug to cool the inside diameter of the tubular parison and ~8~132 -provides an airflow channel through which air may be forced between the cooling plug cylindrical surface and the larger bore portion of the mold blocks whereby a "bell" or expanded sleeve is integrally formed during casting. When the continuous corrugated pipe with integral periodic spacing of the bell sleeve exits the mold tunnel, the pipe is cut into fixed lengths. This provides pipe lengths with a smooth inner bore and an outer corrugated surface with integral bell sleeve at one end, all produced as a continuous casting. The disadvantage of this system is that it consumes an inordinately amount of resin in achieving a smooth inner bore and corrugated outer diameter because the plastic resin is continuous, yet the corrugations do provide enhanced strength and stability for each pipe length.
JARVENKYLA, in Canadian Patent No. 1,231,523 issued 19 March, 1991 discloses a METHOD AND AN APPARATUS FOR
THE EXTRUSION OF PLASTIC PIPES and in one of his embodiments, he discloses the fabrication of a two-walled pipe with integral bell sleeve, an outer corrugated wall integrally attached via its inner diameter to a smooth inner cylindrical sleeve whose inner diameter defines a smooth waterway bore.
Interspaced between grooves and ribs of the outer wall and the outer diameter of the inner sleeve are air spaces which reduce the amount of resin required to form the two-walled pipe and hence, reduce as well the cost and weight thereof. To achieve this, JARVENKYLA
discloses a valve which flows air into an inner diameter of the inner cylindrical sleeve parison, forcing it out to occupy the space defined by one or two of the travelling blocks as a larger diameter annulus forming a bell or joining means intended to allow the joining of one pipe length to another after the pipe is cooled, to become rigid, and is severed.
The inner parison and the outer parison are to be merged in the bell portions of the mold to form the bell or joining means; however, in practice this is not quite achievable because air is entrapped between the inner parison sleeve and the outer parison when air is injected into the internal diameter of the inner parison to force it against the outer parison during the bell formation. The leading and trailing edges of the transition points of the bell with the two-wall pipe trap between the inner and outer parisons, air and hence, the inner and outer parisons are not properly bonded at the leading and trailing edges of the bell unless extreme care to temperature and travel time of the mold is maintained which, in practice, is almost impossible. Secondly, when the formed bell portion, still yet a parison, makes contact with the cooling portion of the plug attached to the mandrel, the air space confined now between the cooling plug outer surface and the inner surfaces of the bell parison is quickly cooled from a parison temperature of approximately 400 F (205 C) to just below 100 F (3$ C) in order to firm up the parison. During this step the bell walls tend to collapse and fold inward.
More particularly, this invention additionally provides an integrally molded joining means of larger internal diameter a bell, into which another length of a pipe can fit and mate so that lengths of pipe can be nested one into the other to form, on site, a pipeline, as may be required.
A third method contemplates the formation of a continuous two-wall corrugated pipe is fashioned and severed into fixed lengths and the bell portion is separately molded and then welded to one of the corrugated outer wall smooth inner bore pipe lengths to achieve an integral bell at the end of a double-walled pipe. The time and cost consequences of such procedure is extravagant and is to be avoided.
THE INVENTION
It is an object of the invention to avoid the collapsing of the bell wall but to allow continuous formation, of a double-walled pipe (outer corrugated wall with a smooth inner bore wall or sleeve) and with an integral bell.
This invention relates to a method of continuously extruding or casting such plastic pipe wherein the corrugated outer wall portion is integrally bonded to a smooth inner sleeve or bore portion so as to form a two-walled pipe, an outer wall with ribs and grooves, the inner portion of the grooves integrally molded to the smooth cylindrical internal sleeve whose inner diameter provides a smooth waterway or inner bore for the smooth flow of water whether fresh, contaminated or sewage. Particularly, the method contemplates the fabrication of such two-walled pipe with air spaces between the outer wall of the smooth inner sleeve and the inner ribs of the outer corrugated wall. This provides enhanced strength to the pipe length and reduces the volume of resin material used to formulate the pipe by as much as a third or more.
The invention further relates to a method and apparatus which extrudes a two-walled plastic pipe with inner and outer walls and an integral joining means and forms the inner wall as a continuous cylindrical sleeve that is bonded to the inner portion of the outer wall.
When the outer wall is formed as a cylinarical corrugation, the inner ribs merge with the outer diameter of the inner wall and periodically during the continuous casting a mold section of greater diameter defines a bell region which ultimately becomes the joining means between two lengths of pipe though continuously manufactured according to the invention by a travelling tunnel mold. The pipe, after molding, is severed at the bell section and the lead portion of the bell section is severed away and the inner wall of the bell portion is also cut away so that an integral bell to a fixed length of corrugated two-walled pipe is formed.
218~132 ._ The invention therefore contemplates ah apparatus for the extrusion of a two-wall plastic pipe with inner and outer walls and an integral joining means comprising a mandrel defining an upstream annular orifice and a downstream annular orifice and a downstream trailing edge therewith, the annular orifices adapted for feeding, from the upstream annular orifice an outer parison and from the downstream annular orifice, an inner parison, both parisons of plasticized plastic material, the mandrel flaring outwardly, at the trailing edge into a truncated conical section, thence, into a cylindrical section whose outer diameter defines the inner diameter of the inner wall of the pipe, molds formed into an endless loop which act as a travelling mold tunnel to surround the mandrel and to travel axially over and along the mandrel each mold defining at least one recess which corresponds to the shape of the outer wall of the two-walled pipe, a channel defined by the mandrel, disposed between the two annular orifices and communicating to a media that is adapted to flow into a plenum defined by that portion of the mandrel between the annular orifices, means for feeding a parison of plasticized plastic out of each of said annular orifices, while travelling the mold tunnel axially over the mandrel and, means for rupturing a wall of the pipe.
Particularly, the travelling molds define one or more adjacent molds with larger inner diameter to form a bell or joining region for the pipe. Rupturing of the wall of the pipe may occur at the bell region, either by penetrating the inner or outer wall.
In that respect, the invention contemplates a method for producing a two-wall pipe with inner and outer walls, and an integrally molded joining means, the inner diameter of which is larger than the outer diameter of the outer wall comprising the steps of moving in sequence, and continuously, in a longitudinal direction of an apparatus, a plurality of outer molds 218~t~2 -each with an inner profile, defining the outer surface of the outer wall of the two-wall pipe the same travelling over a mandrel of smaller diameter forming a first cylindrical parison of plasticized material between the mandrel and travelling mold, forcing the first parison to engage the inner walls of the travelling mold to form the outer surface of the outer wall of the two-wall pipe, injecting between mandrel and the outer wall already formed, an inner cylindrical parison of plasticized plastic material forcing the inner and outer walls to merge along their respective common surfaces to form a two-walled pipe and, rupturing a pipe wall at pre-selected locations as the two-wall pipe traverses the mandrel. Preferably, the method includes rupturing the bell region so as to allow air (ambient air) to enter into a plenum which is defined by the inner and outer walls of the bell region and hence, to prevent the collapsing of the outer wall of the bell region when the parisons are cooled from their molding temperature of approximately 400-F
(205~C) to 100~F (38~C). Preferably, the method contemplates the severing of the pipe after its extraction from the tunnel either by cutting off the lead portion of the bell portion or the trailing portion of the bell portion and discarding to waste the lead portion or the trailing portion, as the case might be, and the inner cylindrical sleeve or inner wall of the bell portion. These may be then ground and re-used as part of the feed material.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example and reference to the accompanying drawings in which:
Figure 1 is a cross-section from prior art patent of JARVENKYLA illustrating the process for creating a bell or double-wall corrugated outside smooth inner bore pipe.
218~132 Figure 2 is a partial cross-section of the resulting product from the process of Figure 1 showing the deformation of the bell section immediately after the continuous pipe exits the casting machine of JARVENKYLA.
Figure 3 is a longitudinal sectional view in detail of the apparatus used for the production of two walled pipes, with integral joining means according to this invention.
Figure 4 is a cross-section of the two-wall pipe, according to the invention just subsequent to its exit from the casting machine.
Figure 5 is a longitudinal cross-section of the pipe of Figure 4 showing the regions of waste after cutting.
Figure 6 is a longitudinal cross-section of two pipes fabricated according to the invention showing the nesting into the bell of the non-bell end portion of a second pipe segment.
Figure 7 is a side elevational view of a two-walled coupling manufactured according to the invention.
Referring to the prior art Figure 1, corresponding references appear in the cross-section Figures 3 and 3A of the present invention and indicate the similar elements. The continuous casting of a two-walled pipe according to the present invention uses an apparatus similar to that disclosed by JARVENKYLA
subject to modifications, as will become apparent herein. Particularly, the molding apparatus includes a plurality of (chill) molds (1) and (2) which travel, chill molds (1) as a first continuous loop chill molds
CORRUGATED PLASTIC PIPE WITH
INTEGRAL JOINING MEANS
This invention relates to continuously extruding or casting of a two-wall corrugated plastic pipe so as to provide a pipe with a smooth internal bore and an integrally molded outer corrugated profile and as well, an integrally molded joining means.
BACKGROUND TO THE INVENTION
The fabrication of single wall corrugated pipe has been known for a number of years. Because of the corrugated inner diameter inherent turbulence of waterflow through the pipe occurs which requires the pipe diameter to be significantly increased in order to allow a given waterflow to occur. It has been recognized that a smooth internal bore pipe could be made of smaller diameter, hence, reduced resin requirement, cost and weight. Corrugations have an advantage in that they add strength to the fabricated pipe and reduce the wall thickness of material used.
LUPKE, in Canadian Patent No. 2,089,183 issued 15 December, 1992, discloses a TRAVELLING MOLD TUNNEL
APPARATUS FOR SMOOTH WALLED PIPE. Particularly the pipe is provided with a smooth inner bore and with an outer corrugated surface, but it is a single wall pipe formed by a travelling mold tunnel and the utilization of a thermal plastic extrusion nozzle to provide a cylindrical or tubular parison into the travelling mold tunnel. A mandrel expands the internal diameter of the parison and urges it against the corrugated inner diameter of the travelling mold to form an outer corrugated surface and a smooth inner bore for the extruded pipe. Additionally, there is provided, periodically, in the travelling mold block chain, one or more adjacent blocks which have a larger inner diameter. The mandrel is provided with a cooling plug to cool the inside diameter of the tubular parison and ~8~132 -provides an airflow channel through which air may be forced between the cooling plug cylindrical surface and the larger bore portion of the mold blocks whereby a "bell" or expanded sleeve is integrally formed during casting. When the continuous corrugated pipe with integral periodic spacing of the bell sleeve exits the mold tunnel, the pipe is cut into fixed lengths. This provides pipe lengths with a smooth inner bore and an outer corrugated surface with integral bell sleeve at one end, all produced as a continuous casting. The disadvantage of this system is that it consumes an inordinately amount of resin in achieving a smooth inner bore and corrugated outer diameter because the plastic resin is continuous, yet the corrugations do provide enhanced strength and stability for each pipe length.
JARVENKYLA, in Canadian Patent No. 1,231,523 issued 19 March, 1991 discloses a METHOD AND AN APPARATUS FOR
THE EXTRUSION OF PLASTIC PIPES and in one of his embodiments, he discloses the fabrication of a two-walled pipe with integral bell sleeve, an outer corrugated wall integrally attached via its inner diameter to a smooth inner cylindrical sleeve whose inner diameter defines a smooth waterway bore.
Interspaced between grooves and ribs of the outer wall and the outer diameter of the inner sleeve are air spaces which reduce the amount of resin required to form the two-walled pipe and hence, reduce as well the cost and weight thereof. To achieve this, JARVENKYLA
discloses a valve which flows air into an inner diameter of the inner cylindrical sleeve parison, forcing it out to occupy the space defined by one or two of the travelling blocks as a larger diameter annulus forming a bell or joining means intended to allow the joining of one pipe length to another after the pipe is cooled, to become rigid, and is severed.
The inner parison and the outer parison are to be merged in the bell portions of the mold to form the bell or joining means; however, in practice this is not quite achievable because air is entrapped between the inner parison sleeve and the outer parison when air is injected into the internal diameter of the inner parison to force it against the outer parison during the bell formation. The leading and trailing edges of the transition points of the bell with the two-wall pipe trap between the inner and outer parisons, air and hence, the inner and outer parisons are not properly bonded at the leading and trailing edges of the bell unless extreme care to temperature and travel time of the mold is maintained which, in practice, is almost impossible. Secondly, when the formed bell portion, still yet a parison, makes contact with the cooling portion of the plug attached to the mandrel, the air space confined now between the cooling plug outer surface and the inner surfaces of the bell parison is quickly cooled from a parison temperature of approximately 400 F (205 C) to just below 100 F (3$ C) in order to firm up the parison. During this step the bell walls tend to collapse and fold inward.
More particularly, this invention additionally provides an integrally molded joining means of larger internal diameter a bell, into which another length of a pipe can fit and mate so that lengths of pipe can be nested one into the other to form, on site, a pipeline, as may be required.
A third method contemplates the formation of a continuous two-wall corrugated pipe is fashioned and severed into fixed lengths and the bell portion is separately molded and then welded to one of the corrugated outer wall smooth inner bore pipe lengths to achieve an integral bell at the end of a double-walled pipe. The time and cost consequences of such procedure is extravagant and is to be avoided.
THE INVENTION
It is an object of the invention to avoid the collapsing of the bell wall but to allow continuous formation, of a double-walled pipe (outer corrugated wall with a smooth inner bore wall or sleeve) and with an integral bell.
This invention relates to a method of continuously extruding or casting such plastic pipe wherein the corrugated outer wall portion is integrally bonded to a smooth inner sleeve or bore portion so as to form a two-walled pipe, an outer wall with ribs and grooves, the inner portion of the grooves integrally molded to the smooth cylindrical internal sleeve whose inner diameter provides a smooth waterway or inner bore for the smooth flow of water whether fresh, contaminated or sewage. Particularly, the method contemplates the fabrication of such two-walled pipe with air spaces between the outer wall of the smooth inner sleeve and the inner ribs of the outer corrugated wall. This provides enhanced strength to the pipe length and reduces the volume of resin material used to formulate the pipe by as much as a third or more.
The invention further relates to a method and apparatus which extrudes a two-walled plastic pipe with inner and outer walls and an integral joining means and forms the inner wall as a continuous cylindrical sleeve that is bonded to the inner portion of the outer wall.
When the outer wall is formed as a cylinarical corrugation, the inner ribs merge with the outer diameter of the inner wall and periodically during the continuous casting a mold section of greater diameter defines a bell region which ultimately becomes the joining means between two lengths of pipe though continuously manufactured according to the invention by a travelling tunnel mold. The pipe, after molding, is severed at the bell section and the lead portion of the bell section is severed away and the inner wall of the bell portion is also cut away so that an integral bell to a fixed length of corrugated two-walled pipe is formed.
218~132 ._ The invention therefore contemplates ah apparatus for the extrusion of a two-wall plastic pipe with inner and outer walls and an integral joining means comprising a mandrel defining an upstream annular orifice and a downstream annular orifice and a downstream trailing edge therewith, the annular orifices adapted for feeding, from the upstream annular orifice an outer parison and from the downstream annular orifice, an inner parison, both parisons of plasticized plastic material, the mandrel flaring outwardly, at the trailing edge into a truncated conical section, thence, into a cylindrical section whose outer diameter defines the inner diameter of the inner wall of the pipe, molds formed into an endless loop which act as a travelling mold tunnel to surround the mandrel and to travel axially over and along the mandrel each mold defining at least one recess which corresponds to the shape of the outer wall of the two-walled pipe, a channel defined by the mandrel, disposed between the two annular orifices and communicating to a media that is adapted to flow into a plenum defined by that portion of the mandrel between the annular orifices, means for feeding a parison of plasticized plastic out of each of said annular orifices, while travelling the mold tunnel axially over the mandrel and, means for rupturing a wall of the pipe.
Particularly, the travelling molds define one or more adjacent molds with larger inner diameter to form a bell or joining region for the pipe. Rupturing of the wall of the pipe may occur at the bell region, either by penetrating the inner or outer wall.
In that respect, the invention contemplates a method for producing a two-wall pipe with inner and outer walls, and an integrally molded joining means, the inner diameter of which is larger than the outer diameter of the outer wall comprising the steps of moving in sequence, and continuously, in a longitudinal direction of an apparatus, a plurality of outer molds 218~t~2 -each with an inner profile, defining the outer surface of the outer wall of the two-wall pipe the same travelling over a mandrel of smaller diameter forming a first cylindrical parison of plasticized material between the mandrel and travelling mold, forcing the first parison to engage the inner walls of the travelling mold to form the outer surface of the outer wall of the two-wall pipe, injecting between mandrel and the outer wall already formed, an inner cylindrical parison of plasticized plastic material forcing the inner and outer walls to merge along their respective common surfaces to form a two-walled pipe and, rupturing a pipe wall at pre-selected locations as the two-wall pipe traverses the mandrel. Preferably, the method includes rupturing the bell region so as to allow air (ambient air) to enter into a plenum which is defined by the inner and outer walls of the bell region and hence, to prevent the collapsing of the outer wall of the bell region when the parisons are cooled from their molding temperature of approximately 400-F
(205~C) to 100~F (38~C). Preferably, the method contemplates the severing of the pipe after its extraction from the tunnel either by cutting off the lead portion of the bell portion or the trailing portion of the bell portion and discarding to waste the lead portion or the trailing portion, as the case might be, and the inner cylindrical sleeve or inner wall of the bell portion. These may be then ground and re-used as part of the feed material.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example and reference to the accompanying drawings in which:
Figure 1 is a cross-section from prior art patent of JARVENKYLA illustrating the process for creating a bell or double-wall corrugated outside smooth inner bore pipe.
218~132 Figure 2 is a partial cross-section of the resulting product from the process of Figure 1 showing the deformation of the bell section immediately after the continuous pipe exits the casting machine of JARVENKYLA.
Figure 3 is a longitudinal sectional view in detail of the apparatus used for the production of two walled pipes, with integral joining means according to this invention.
Figure 4 is a cross-section of the two-wall pipe, according to the invention just subsequent to its exit from the casting machine.
Figure 5 is a longitudinal cross-section of the pipe of Figure 4 showing the regions of waste after cutting.
Figure 6 is a longitudinal cross-section of two pipes fabricated according to the invention showing the nesting into the bell of the non-bell end portion of a second pipe segment.
Figure 7 is a side elevational view of a two-walled coupling manufactured according to the invention.
Referring to the prior art Figure 1, corresponding references appear in the cross-section Figures 3 and 3A of the present invention and indicate the similar elements. The continuous casting of a two-walled pipe according to the present invention uses an apparatus similar to that disclosed by JARVENKYLA
subject to modifications, as will become apparent herein. Particularly, the molding apparatus includes a plurality of (chill) molds (1) and (2) which travel, chill molds (1) as a first continuous loop chill molds
(2) as a second continuous loop in the fashion disclosed by JARVENKYA. Each chill mold (1) and (2) travels in the directions of arrows (D) and are each provided with at least one venting channel (3), preferably more communicating through the chill molds (1) and (2) to the inner corrugated cylindrical profile bore (11) and (22) which will define the outer surface or skin (16) of the outer corrugated wall (17) of a two-walled pipe (18) which will be cast with an inner cylindrical sleeve (19). In fact, it is preferred that each chill mold (1) and (2) have more than one corrugation and in Figure 1, three corrugated annular recesses are shown, although more could be provided depending upon the pipe diameter being cast and other parameters, which those skilled in the art will understand.
At pre-determined intervals along each endless loop chill mold (1) and (2) are a pair of mirror chill molds (4) and ( 6) in relation to continuous loop (2); and, (5) and (7) in relation to continuous loop (1), each pair (4-6,5-7) define a larger bore semi-annulus (30), for loop (1), and for loop (2), (40). The mold bell bore recesses (30-40) spatially disposed along each of the endless loops so the length of corrugated pipe with bell is formed every 3 to 4 metres. This produces pipe lengths (18) of the preferred length in a fashion that will be described. The adjacent mirror molds (4) and (6) and (5) and ( 7) do not mate with each other when they are closed to form the cylindrical larger bell bore recess (30-40) but define therebetween a small 2 5 vent space referenced ( 50).
There is additionally provided a mandrel (8) having a straight portion conically extending into an enlarged midstream cylindrical portion (9") and a downstream portion (9') which collectively define an annular recess (10). The downstream face (13) of the midstream portion (9") communicates with a channel ( 15) through a valve (V) to a source (not shown) of pressure medium, such as air which, when the valve (V) opens flows into the annular recess or groove (10) and hence, into the plenum inner surface of the parison pipe in a fashion as will now be described.
A cylindrical parison of plasticized plastic material is fed into chill molds (la) and (2a) as a co-2182~32 -axial cylindrical stream as a result of a separating cylindrical section (25) being integral with the parison extruder, (not shown) and in that respect section 25 extends well into the chill molds (lA) and (2A), as shown in Figure 1. In this fashion, an inner cylindrical parison stream (Pi) is formed as well as an outer parison stream (PO)- The two cylindrical parisons streams travel with chill molds (1) and (2) in direction (D). When the outer parison Po) is formed, the parison will cling to the inner ribbed wall of the chill molds (la) and (2a) because of a slight increase of pressure applied in the zone lPSI to the degree of lPSI above ambient pressure or alternatively, the exterior orifices of the channels (3) are provided with a vacuum which "sucks" the parison Po) against the inner ribs of the molds (la) and (2a) to form the outer skin (16) of the outer wall (17). The conical portion (8') of the mandrel (8) forces the inner parison (Pi) against the inner ribs of the outer parison (Po) at (60) making a bonding union between each rib -inner parison (Pi) interface (60), see also Figure 2 and forming the inner cylindrical sleeve (19) of the two-walled pipe (18). When the bell section (30) is over the cooling plug (9'), the air confined between the outer diameter of the cylindrical downstream cooling plug end portion (9') and the bell (30), tends to cool causing a vacuum to be created and the bell parison to collapse, (30') as shown in Figure 2. Also, the upstream and downstream inner and outer parisons Po) and (Pl) of the bell portion (30') tend to separate during cooling leaving an annular air space (32) at the upstream end and (34) at the downstream end of the bell (30). Good cohesion of the two-ply portion of the bell wall (30') cannot be assured.
THE PREFERRED EMBODIMENT
Referring to the cross-sectional Figure 3, similar references to the prior art Figure 1 have been used for ~- 21~ 2 similar parts. The showing of the discreet molds (1) and (2) and the venting channels (3) has been eliminated for clarity.
The mandrel (9) is provided with an upstream annular orifice (20) out of which~exudes the outer parison Po).
The mandrel (9) has an annular recess (10) out of which comes a stream of air to pressurize the internal diameter of the outer parison Po) and to push the parison against the walls (1) and (2) which are vented but are not shown, of the travelling mold whereby the outer corrugated wall (17) is formed. Downstream, there is the cylindrical section (25) which defines at its downstream end that is the upstream end of the bevel (8'), an annular orifice (29) out of which exudes the inner parison (Pi). The cooling plug end portion (9') has an outer helical race, the floor of which communicates to channels (72) which make connection, not shown, to a vacuum so as to apply an inner vacuum to the inner skin of the inner parison Po) while the outer diameter of the cooling plug (9') is sized to the inner diameter of the inner parison (Pi). This allows the sliding of the inner parison along the cooling plug (9') while the inner parison makes an interface (60) with the inner ribs of the outer wall (17) and merges therewith so as to bond. The plug (9') is also provided with a source of cooling, not shown, as by a water current and the parisons (P~) and (P2) are cooled thereby. The downstream face (13) of the cooling plug (9') carries at least one, but preferably diametrically opposed reciprocating plungers (80), the end of each plunger (80) being pointed at (81). When the leading edge (32") of the bell portion (30") crosses into registration with the plunger (80), the plungers are activated moving the plunger tip (82) into the still soft inner wall (19) rupturing the same and creating orifices (85) as shown. As the bell portion (30') thus cools, the annular space or plenum (30P) defined between the inner sleeve (19) and the bell (30') is 2182~32 -supplied with ambient and cooling air to keep the bell air space or plenum (30P) at near ambient temperature.
This inhibits distortion of the bell (30") during cooling. During this process, the parison (Po) and (Pi) exit their respective annular orifices (20) and (29) at a temperature of approximately 400 F (205 C) but when the molded pipe exits the tunnel mold and after rupturing of the inner wall (19) as aforesaid, the temperature of the continuous pipe, prior to severing, as will be described, is at about lOO F or 38 C.
After the pipe exits the travelling mold, and as seen in Figure 4, the pipe is severed firstly at cut (Cl), severing the pipe (18) at a point just at the juncture (6), seen in Figure 4, and bell transition annulus (31) is then cut away as it forms the lead segment (310) of the bell (30") and hence, is then severed at (C2) with a saw or the like in a similar fashion as with cut (Cl). The inner wall (19B) of the bell section is then severed at cut (C3) just prior to the juncture of the trailing transition (33) of the bell (30'). The inner bell sleeve (19B) and the lead annular piece (310) are ground and recycled to be put back as feed for the extruder.
Referring to Figure 6, the non bell end of a pipe section nests into the bell (30") because the inner diameter of the bell (30") is sized to the outer diameter of the rib portion (16) of the outer wall (17).
Referring now to Figure 7, a two-walled corrugated pipe coupling (181) can be formed with opposite bell ends (130), interconnected by co-axial inner cylindrical wall (119) and outer corrugated wall (117) with the inner ribs of the outer wall (117) bonded to the outer surface of the inner wall (119) in the fashion earlier described. If desired, the molds that traverse the travelling mold tunnel can be arranged so that a coupling element (181) is fabricated and interspaced between a pipe length (18), as shown in Figures 3 and 3A, and then a given pipe length (18), as in Figures 5 and 6. Generally, the length of a coupling (181) will be about a third of a metre so as to allow the distance betw,een bell ends (130) to be sufficient so by a subsequent step, not part of the invention, a hole could be cut into the two-walled corrugated region (185) and "T" welded therein.
At pre-determined intervals along each endless loop chill mold (1) and (2) are a pair of mirror chill molds (4) and ( 6) in relation to continuous loop (2); and, (5) and (7) in relation to continuous loop (1), each pair (4-6,5-7) define a larger bore semi-annulus (30), for loop (1), and for loop (2), (40). The mold bell bore recesses (30-40) spatially disposed along each of the endless loops so the length of corrugated pipe with bell is formed every 3 to 4 metres. This produces pipe lengths (18) of the preferred length in a fashion that will be described. The adjacent mirror molds (4) and (6) and (5) and ( 7) do not mate with each other when they are closed to form the cylindrical larger bell bore recess (30-40) but define therebetween a small 2 5 vent space referenced ( 50).
There is additionally provided a mandrel (8) having a straight portion conically extending into an enlarged midstream cylindrical portion (9") and a downstream portion (9') which collectively define an annular recess (10). The downstream face (13) of the midstream portion (9") communicates with a channel ( 15) through a valve (V) to a source (not shown) of pressure medium, such as air which, when the valve (V) opens flows into the annular recess or groove (10) and hence, into the plenum inner surface of the parison pipe in a fashion as will now be described.
A cylindrical parison of plasticized plastic material is fed into chill molds (la) and (2a) as a co-2182~32 -axial cylindrical stream as a result of a separating cylindrical section (25) being integral with the parison extruder, (not shown) and in that respect section 25 extends well into the chill molds (lA) and (2A), as shown in Figure 1. In this fashion, an inner cylindrical parison stream (Pi) is formed as well as an outer parison stream (PO)- The two cylindrical parisons streams travel with chill molds (1) and (2) in direction (D). When the outer parison Po) is formed, the parison will cling to the inner ribbed wall of the chill molds (la) and (2a) because of a slight increase of pressure applied in the zone lPSI to the degree of lPSI above ambient pressure or alternatively, the exterior orifices of the channels (3) are provided with a vacuum which "sucks" the parison Po) against the inner ribs of the molds (la) and (2a) to form the outer skin (16) of the outer wall (17). The conical portion (8') of the mandrel (8) forces the inner parison (Pi) against the inner ribs of the outer parison (Po) at (60) making a bonding union between each rib -inner parison (Pi) interface (60), see also Figure 2 and forming the inner cylindrical sleeve (19) of the two-walled pipe (18). When the bell section (30) is over the cooling plug (9'), the air confined between the outer diameter of the cylindrical downstream cooling plug end portion (9') and the bell (30), tends to cool causing a vacuum to be created and the bell parison to collapse, (30') as shown in Figure 2. Also, the upstream and downstream inner and outer parisons Po) and (Pl) of the bell portion (30') tend to separate during cooling leaving an annular air space (32) at the upstream end and (34) at the downstream end of the bell (30). Good cohesion of the two-ply portion of the bell wall (30') cannot be assured.
THE PREFERRED EMBODIMENT
Referring to the cross-sectional Figure 3, similar references to the prior art Figure 1 have been used for ~- 21~ 2 similar parts. The showing of the discreet molds (1) and (2) and the venting channels (3) has been eliminated for clarity.
The mandrel (9) is provided with an upstream annular orifice (20) out of which~exudes the outer parison Po).
The mandrel (9) has an annular recess (10) out of which comes a stream of air to pressurize the internal diameter of the outer parison Po) and to push the parison against the walls (1) and (2) which are vented but are not shown, of the travelling mold whereby the outer corrugated wall (17) is formed. Downstream, there is the cylindrical section (25) which defines at its downstream end that is the upstream end of the bevel (8'), an annular orifice (29) out of which exudes the inner parison (Pi). The cooling plug end portion (9') has an outer helical race, the floor of which communicates to channels (72) which make connection, not shown, to a vacuum so as to apply an inner vacuum to the inner skin of the inner parison Po) while the outer diameter of the cooling plug (9') is sized to the inner diameter of the inner parison (Pi). This allows the sliding of the inner parison along the cooling plug (9') while the inner parison makes an interface (60) with the inner ribs of the outer wall (17) and merges therewith so as to bond. The plug (9') is also provided with a source of cooling, not shown, as by a water current and the parisons (P~) and (P2) are cooled thereby. The downstream face (13) of the cooling plug (9') carries at least one, but preferably diametrically opposed reciprocating plungers (80), the end of each plunger (80) being pointed at (81). When the leading edge (32") of the bell portion (30") crosses into registration with the plunger (80), the plungers are activated moving the plunger tip (82) into the still soft inner wall (19) rupturing the same and creating orifices (85) as shown. As the bell portion (30') thus cools, the annular space or plenum (30P) defined between the inner sleeve (19) and the bell (30') is 2182~32 -supplied with ambient and cooling air to keep the bell air space or plenum (30P) at near ambient temperature.
This inhibits distortion of the bell (30") during cooling. During this process, the parison (Po) and (Pi) exit their respective annular orifices (20) and (29) at a temperature of approximately 400 F (205 C) but when the molded pipe exits the tunnel mold and after rupturing of the inner wall (19) as aforesaid, the temperature of the continuous pipe, prior to severing, as will be described, is at about lOO F or 38 C.
After the pipe exits the travelling mold, and as seen in Figure 4, the pipe is severed firstly at cut (Cl), severing the pipe (18) at a point just at the juncture (6), seen in Figure 4, and bell transition annulus (31) is then cut away as it forms the lead segment (310) of the bell (30") and hence, is then severed at (C2) with a saw or the like in a similar fashion as with cut (Cl). The inner wall (19B) of the bell section is then severed at cut (C3) just prior to the juncture of the trailing transition (33) of the bell (30'). The inner bell sleeve (19B) and the lead annular piece (310) are ground and recycled to be put back as feed for the extruder.
Referring to Figure 6, the non bell end of a pipe section nests into the bell (30") because the inner diameter of the bell (30") is sized to the outer diameter of the rib portion (16) of the outer wall (17).
Referring now to Figure 7, a two-walled corrugated pipe coupling (181) can be formed with opposite bell ends (130), interconnected by co-axial inner cylindrical wall (119) and outer corrugated wall (117) with the inner ribs of the outer wall (117) bonded to the outer surface of the inner wall (119) in the fashion earlier described. If desired, the molds that traverse the travelling mold tunnel can be arranged so that a coupling element (181) is fabricated and interspaced between a pipe length (18), as shown in Figures 3 and 3A, and then a given pipe length (18), as in Figures 5 and 6. Generally, the length of a coupling (181) will be about a third of a metre so as to allow the distance betw,een bell ends (130) to be sufficient so by a subsequent step, not part of the invention, a hole could be cut into the two-walled corrugated region (185) and "T" welded therein.
Claims (23)
1. An apparatus for the extrusion of a two-wall plastic pipe with inner and outer walls and an integral joining means comprising:
(a) a mandrel defining an upstream annular orifice and a downstream annular orifice and a downstream trailing edge therewith, the annular orifices adapted for feeding, from the upstream annular orifice an outer parison and from the downstream annular orifice, an inner parison, both parisons of plasticized plastic material, the mandrel flaring outwardly, at the trailing edge into a truncated conical section, thence, into a cylindrical section whose outer diameter defines the inner diameter of the inner wall of the pipe;
(b) molds formed into an endless loop which act as a travelling mold tunnel to surround the mandrel and to travel axially over and along the mandrel each mold defining at least one recess which corresponds to the shape of the outer wall of the two-walled pipe;
(c) a channel defined by the mandrel, disposed between the two annular orifices and communicating to a media that is adapted to flow into a plenum defined by that portion of the mandrel between the annular orifices;
(d) means for feeding a parison of plasticized plastic out of each of said annular orifices, while travelling the mold tunnel axially over the mandrel;
and, (e) means for rupturing a wall of the pipe.
(a) a mandrel defining an upstream annular orifice and a downstream annular orifice and a downstream trailing edge therewith, the annular orifices adapted for feeding, from the upstream annular orifice an outer parison and from the downstream annular orifice, an inner parison, both parisons of plasticized plastic material, the mandrel flaring outwardly, at the trailing edge into a truncated conical section, thence, into a cylindrical section whose outer diameter defines the inner diameter of the inner wall of the pipe;
(b) molds formed into an endless loop which act as a travelling mold tunnel to surround the mandrel and to travel axially over and along the mandrel each mold defining at least one recess which corresponds to the shape of the outer wall of the two-walled pipe;
(c) a channel defined by the mandrel, disposed between the two annular orifices and communicating to a media that is adapted to flow into a plenum defined by that portion of the mandrel between the annular orifices;
(d) means for feeding a parison of plasticized plastic out of each of said annular orifices, while travelling the mold tunnel axially over the mandrel;
and, (e) means for rupturing a wall of the pipe.
2. The apparatus as claimed in claim 1, wherein at least a pair of opposite molds define a larger internal cylindrical cavity than the other molds and hence, a bell region for the pipe.
3. The apparatus as claimed in claim 2, wherein means (e) ruptures the bell region of the pipe.
4. The apparatus as claimed in claim 2, wherein means (e) ruptures the inner wall of the bell region of the pipe.
5. The apparatus as claimed in claim 2, 3, or 4 wherein the bell region of the outer wall has an internal diameter sized fractionally larger than the outer diameter of the outer wall.
6. The apparatus as claimed in claim 2, 3, or 4 wherein the mold recess defines a rib and recess so as to construct a corrugated outer wall.
7. The apparatus as claimed in claim 2, 3, or 4, wherein the diameter of the cylindrical section of the mandrel is sized so that the inner parison outer wall is fused to the inner ribs of the outer parison.
8. A method for producing a two-wall pipe with inner and outer walls, and an integrally molded joining means, the inner diameter of which is larger than the outer diameter of the outer wall comprising the steps of:
(a) moving in sequence, and continuously, in a longitudinal direction of an apparatus, a plurality of outer molds each with an inner profile, defining the outer surface of the outer wall of the two-wall pipe the same travelling over a mandrel of smaller diameter;
(b) forming a first cylindrical parison of plasticized material between the mandrel and travelling mold;
(c) forcing the first parison to engage the inner walls of the travelling mold to form the outer surface of the outer wall of the two-wall pipe;
(d) injecting between mandrel and the outer wall already formed, an inner cylindrical parison of plasticized plastic material;
(e) forcing the inner and outer walls to merge along their respective common surfaces to form a two-walled pipe; and, (f) rupturing a pipe wall at pre-selected locations as the two-wall pipe traverses the mandrel.
(a) moving in sequence, and continuously, in a longitudinal direction of an apparatus, a plurality of outer molds each with an inner profile, defining the outer surface of the outer wall of the two-wall pipe the same travelling over a mandrel of smaller diameter;
(b) forming a first cylindrical parison of plasticized material between the mandrel and travelling mold;
(c) forcing the first parison to engage the inner walls of the travelling mold to form the outer surface of the outer wall of the two-wall pipe;
(d) injecting between mandrel and the outer wall already formed, an inner cylindrical parison of plasticized plastic material;
(e) forcing the inner and outer walls to merge along their respective common surfaces to form a two-walled pipe; and, (f) rupturing a pipe wall at pre-selected locations as the two-wall pipe traverses the mandrel.
9. The method as claimed in claim 7, wherein at least one outer pair of the outer molds is of larger internal diameter than the adjacent molds so as to form an integral bell region of the pipe.
10. The method as claimed in claim 9, wherein the rupturing step (f) ruptures the bell region.
11. The method as claimed in claim 8, 9, or 10 wherein the rupturing step (f) ruptures the inner wall.
12. The method as claimed in claim 8, 9, or 10 including the additional step, of severing the pipe after its extraction from the mold tunnel at the bell region.
13. The method as claimed in claim 8, 9, or 10 including the additional steps, of severing the pipe after its extraction from the mold tunnel at the bell region and cutting away the internal wall of the bell region.
14. The method as claimed in claim 8, 9, or 10, including the additional step, of severing the pipe after its extraction from the mold tunnel at the upstream interface of the bell region with the inner and outer walls of the pipe.
15. The method as claimed in claim 8, 9, or 10 wherein the rupturing step (f) ruptures the inner wall and the additional step, of severing the pipe after its extraction from the mold tunnel at the upstream interface of the bell region with the inner and outer walls of the pipe.
16. The method as claimed in claim 8, 9, or 10 including the additional steps, of severing the pipe after its extraction from the mold tunnel at the upstream interface of the bell region with the inner and outer walls of the pipe and the internal wall of the bell region at its downstream interface with the outer wall.
17. The method as claimed in claim 8, 9, or 10 including the additional steps, of severing the pipe after its extraction from the mold tunnel at the upstream interface of the bell region with the inner and outer walls of the pipe and the internal wall of the bell region at its downstream interface with the inner and outer walls and severing the internal wall of the bell region at its downstream interface with the outer wall.
18. The method as claimed in claim 8, 9, or 10 wherein the rupturing step (f) ruptures the inner wall and the additional step, of severing the pipe after its extraction from the mold tunnel at the upstream interface of the bell region with the inner and outer walls of the pipe and severing a lead segment from the leading end of the bell portion.
19. The method as claimed in claim 8, 9, or 10 including the additional steps, of severing the pipe after its extraction from the mold tunnel at the upstream interface of the bell region with the inner and outer walls of the pipe and the internal wall of the bell region at its downstream interface with the outer wall and severing a lead segment from the leading end of the bell portion.
20. The method as claimed in claim 8, 9, or 10 including the additional steps, of severing the pipe after its extraction from the mold tunnel at the upstream interface of the bell region with the inner and outer walls of the pipe and the internal wall of the bell region at its downstream interface with the inner and outer walls and severing the internal wall of the bell region at its downstream interface with the outer wall and severing a lead segment from the leading end of the bell portion.
21. The method as claimed in claim 8, 9, or 10 wherein the rupturing step (f) ruptures the inner wall and the additional step, of severing the pipe after its extraction from the mold tunnel at the downstream interface of the bell region with the inner and outer walls of the pipe and severing an end segment from the bell portion.
22. The method as claimed in claim 8, 9, or 10 including the additional steps, of severing the pipe after its extraction from the mold tunnel at the downstream interface of the bell region with the inner and outer walls of the pipe and the internal wall of the bell region at its downstream interface with the outer wall and severing an end segment from the bell portion.
23. The method as claimed in claim 8, 9, or 10 including the additional steps, of severing the pipe after its extraction from the mold tunnel at the downstream interface of the bell region with the inner and outer walls of the pipe and the internal wall of the bell region at its downstream interface with the inner and outer walls and severing the internal wall of the bell region at its downstream interface with the outer wall and severing an end segment from the bell portion.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002182132A CA2182132A1 (en) | 1996-07-26 | 1996-07-26 | Continuous casting of a two-wall corrugated plastic pipe with integral joining means |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002182132A CA2182132A1 (en) | 1996-07-26 | 1996-07-26 | Continuous casting of a two-wall corrugated plastic pipe with integral joining means |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2182132A1 true CA2182132A1 (en) | 1998-01-27 |
Family
ID=4158666
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002182132A Abandoned CA2182132A1 (en) | 1996-07-26 | 1996-07-26 | Continuous casting of a two-wall corrugated plastic pipe with integral joining means |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2182132A1 (en) |
-
1996
- 1996-07-26 CA CA002182132A patent/CA2182132A1/en not_active Abandoned
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| Date | Code | Title | Description |
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| FZDE | Discontinued |