Fitting installation process and apparatus for a molded plastic vessel

Abstract: The invention relates to a method of manufacturing a fluid containing vessel having a fitting. The steps include forming a liner (10), providing a preformed fitting (14) having a flange; installing an insert (24) in the fitting; and positioning the fitting (14) on a wall of the liner (10) and welding the insert to the wall. Additional steps include filament winding the liner, said filaments capturing the fitting flange against the wall; and cutting a hole through the wall of the liner inside the fitting to create a passage through the fitting and liner wall. Preferably, the fitting (14) defines a passage (18) therethrough and the insert (24) is installed in the passage (18). The insert preferably has a flange (26) that engages the fitting to retain the fitting on the liner. The passage preferably communicates with an interior of the liner through the hole. When the liner and insert are made of materials having substantially similar melting temperatures, they are preferably heated to about the same temperature. When the liner (10) and insert (24) have different melting temperatures, they are preferably heated to different temperatures. The liner 10) and insert (24) are preferably made of materials compatible for welding to each other, preferably plastic. The liner (10) may be generally cylindrical, and the fitting (14) may be located on a generally cylindrical side wall of the liner. The step of welding may include heating the insert (24) and an area of the liner (10) and pressing the insert (24) into the liner to bond therewith.

Description: This invention relates generally to the field of plastic vessels and specifically to a process for installing a fitting on such a vessel. Molded vessels have numerous applications for containing fluids. The vessels are made by any of several plastic forming processes, including rotational molding and blow molding. Many of the fluids are contained at high pressure. Therefore, the vessels are reinforced by filaments wound on the outer surface of the vessel, as described, for example, in U.S. Patents Nos. 3,945,578 to Kaminsky and 5,012,950 to Knappe. Such vessels need one, and frequently several, ports for filling or emptying the vessel. The ports are commonly provided as a rigid fitting adapted to connect to a hose or pipe. Such fittings can be provided during the molding process. For example, a metal fitting can be held in the mold and the plastic molded around the fitting. This method, however, cannot be used to add a fitting after molding. Moreover, reconfiguring a mold is costly, thus, fittings cannot be located at different locations based on specified applications. U.S. Patent No. 4,685,589 to Benton describes one way of installing a fitting after molding and before winding a vessel. An elastic seal is disposed between the fitting and the vessel. U.S. Patent No. 5 006 197 describes a system for fusion bonding several attachments to a relatively large and bulky thermoplastic article which employs means for fixedly securing the article, and a movable fixture selectively positionable relative to the thermoplastic article, however there is no disclosure or suggestion of a method as set out in claim 1 herein. Still, the need remains for a method of fabricating a fitting that allows the fitting to be located after molding of the vessel. The fitting should be firmly secured on the vessel and bonded therewith prior to winding. The present invention provides a method of manufacturing a fluid-containing vessel having a fitting, comprising the steps of: forming a liner defining the vessel; providing a preformed fitting; installing an insert in the fitting the insert comprising means for engaging the fitting to firmly secure the fitting on the liner and bond it therewith; positioning the fitting on a wall of the liner; and welding the insert to the wall. Preferably, the fitting defines a passage therethrough, and the insert is installed in the passage. The insert preferably has a flange that engages the fitting to retain the fitting on the liner. The passage preferably communicates with an interior of the liner through the hole. When the liner and insert are made of materials having substantially similar melting temperatures, they are preferably heated to about the same temperature. When the liner and insert have different melting temperatures, they are preferably heated to different temperatures. The liner and insert are made of plastic materials compatible for welding to each other. The liner may be generally cylindrical, and the fitting may be located on a generally cylindrical side wall of the liner. The step of welding may include heating the insert and an area of the liner and pressing the insert into the liner to bond therewith. According to one aspect of the invention, the method includes rotationally molding the liner of plastic material having a generally cylindrical shape. The fitting is preformed with the flange and passage therethrough. The insert, of the same material as the liner, is installed in the passage of the fitting, and the insert flange engages the fitting. Heating the insert and an area of the cylindrical wall of the liner where the fitting is to be installed softens the fitting and the area of the wall. The flange of the fitting is installed on the area of the wall and the insert is pressed into the area so as to bond the insert to the wall. Filament winding of the liner captures the fitting flange against the wall. Cutting a hole through the wall of the liner inside the fitting creates a port through the passage. The invention also provides an apparatus for installing a fitting on a molded vessel liner. The apparatus includes means for supporting the fitting and an insert near the liner; a heater; means for positioning the heater between the fitting and the liner for heating the insert and an area of the liner; and means for positioning the fitting on the liner and pressing the insert into the liner to weld the insert to the liner. According to a preferred aspect of the invention, the apparatus for installing the fitting on the molded vessel liner includes a platform. A mounting head is movably mounted on the platform and adapted for supporting the fitting and the insert near the liner, positioning the fitting on the liner, and pressing the insert into the liner. A driver is adapted to move the mounting head. A heat mirror is movably mounted on the platform on a support arm having the heat mirror pivotably mounted thereon. The support arm is adapted for positioning the heater between the fitting and the liner. Fig. 1 shows a partially exploded side elevational view of an apparatus for installing a fitting on a liner and a partial end view of the liner; Fig. 2 shows a top view of the apparatus, assembled fitting, and liner of Fig. 1; and Fig. 3 shows an isometric view of the wound vessel with the fitting installed thereon. Referring to Fig. 1, a molded tank liner 10 for a vessel is made from a suitable polymer, such as polyethylene, by rotational molding, blow molding, or the like. The liner 10 is conventional and can have any of a number of shapes and constructions including a side wall 12 that defines an internal volume. A fitting 14 has a flange 16 and a cylindrical passage 18 therethrough. The fitting is made of metal, a composite, sheet molding compound, bulk molding compound or other suitable durable material. The fitting 14 can be threaded or otherwise suitable for connecting to another fitting or a conduit. A pair of threaded bores 20 are provided in a face of the fitting 14. An insert 22 has a cylindrical body 24 adapted to fit in the cylindrical passage 18 of the fitting 14. The insert 22 is preferably molded from a material compatible with the liner 10 and adapted to be bonded therewith by welding, such as polyethylene. The insert 22 is provided with an annular flange 26 for preventing the insert from passing through the passage 18 of the fitting 14. The body defines an edge 27 adapted to be flush with or extend slightly from the flange 16 of the fitting 12. A pair of holes 28 corresponding with the threaded bores 20 are provided through the flange 26. An installation apparatus 30 is adapted to be located near the liner 10 and includes a vertically and laterally adjustable platform 32. The platform is adjustable by manual or powered devices, such as cranks and threaded shafts. A horizontally movable mounting head 34 is supported on a horizontal shaft 36 of a driver, such as a hydraulic or pneumatic cylinder 38, mounted to the platform 32. The cylinder 38 is powered by fluid controlled by a head controller 40. The mounting head 34 has a front face 42 adapted to engage the flange 26 of the insert 22. A pair of holes 44 corresponding with the insert holes 28 are provided through the head 34. A pair of bolts 46 are installed through the holes 44, 28 and threaded into the bores 20 to mount the fitting 14 and insert 22 on the mounting head 34. Alternatively, the fitting 14 can be mounted on the head 34 by a clamp or other suitable mounting means. The fitting 14 is firmly mounted so that the insert flange 26 engages the fitting 14. Referring to Fig. 2, a heater 48, such as a two sided heat mirror, is disposable between the mounting head 34 and the liner 10. A pair of heating spigots 49 conforming to the wall 12 and insert 22 direct and focus heat emanating from the heater 48. Alternatively, the heater can be two separate one-sided heat mirrors or other heating means. The heater can be hand held or supported on a suitable stationary or movable structure. The two sides of the heater 48 are separately controlled by a heater control 51. Preferably, the heater 48 is carried on the platform 32 by a pivotable support arm 50 and a brace arm 52. The support arm 50 is adapted to pivot, thereby moving the heater 48 to a vertical position providing clearance for the head 34 to move the fitting 14 toward the liner 10. In a horizontal position shown, the heater 48 is held at a constant level and prevented from shifting by the brace arm 52. A rotary grinder 54 having a cutting tool 56 powered by a motor 58 is provided on the platform 32 or separately therefrom. A hand held grinder 54 is suitable. In operation, referring to Figs. 1 and 2, the installation apparatus 30 is located near the previously molded liner 10. The heater 48 is moved to its horizontal position and located proximate to a location on the liner 10 where the fitting 14 is to be installed. The mounting head 34 is moved to a retracted position away from the heater 48. The insert 22 is installed in the passage 18 of the fitting 14 so that the insert flange 26 engages the fitting 14. The fitting 14 and insert 22 are mounted on the mounting head 34 with the bolts 46. The head 34, insert 22 and fitting 14 are moved to an intermediate position wherein the flange 16 of the fitting 14 and edge 27 of the insert are proximate to the heater 48. The heater 48 is activated to heat the edge 27 of the insert 22 and an area of the wall 12 of the liner 10. The edge 27 and wall 12 are softened or melted to a point at which they can be bonded together. The heater 48 is automatically or manually controllable to properly heat the edge 27 and wall 12. The heat required depends on the materials. Opposite sides of the heater 48 can be separately controlled to provide the proper temperature for different insert 22 and liner 10 materials. If the application allows, the heater can be automatically controlled to provide adequate heating for successive liners and fittings. The heater 48 is deactivated and the support arm 50 is pivoted to move the heater 48 to its vertical position. The mounting head 34 is moved to an extended position wherein the flange 16 is pressed against the wall 12 and the insert 22 is welded to the wall 12. The fitting 14 is held against the wall under pressure from the cylinder 38 for a sufficient time to bond the insert 22 to the wall 12. The time and pressure depend on the materials and will be apparent to one skilled in the art of plastics. The fitting 14 is held in place without pressure until the insert 22 and wall 12 have cooled sufficiently to hold the fitting 14. The mounting head 34 is separated from the insert 22 and fitting 14, by removing the bolts 46, and the mounting head 34 is retracted. The grinder 54 is then used to remove the portion of the wall 12 inside the insert 22 to cut or grind open the interior of the liner 10 and place the interior of the liner in communication with the passage 18. Finally the liner is filament 60 wound in a conventional manner, as shown in Fig. 3. The filaments 60 pass over and capture the flange 16 of the fitting to securely hold the fitting on the liner 10. If it is necessary to entirely remove the insert 22, the liner 10 should be filament wound prior to grinding or cutting out the insert 22 and portion of the wall 12. The fitting 14 is then suitable for connecting conduits to the vessel. The present disclosure describes several embodiments of the invention, however, the invention is not limited to these embodiments. For example, other devices and fittings, such as sight gauges, flanges, etc. can be installed on other vessels according to the present invention. Other variations are contemplated to be within the scope of the appended claims.

Claims: A method of manufacturing a fluid-containing vessel having a fitting, comprising the steps of: forming a liner (10) defining the vessel; providing a preformed fitting (14); installing an insert (22) in the fitting the insert (22) comprising means (26) for engaging the fitting to firmly secure the fitting on the liner and bond it therewith; positioning the fitting (14) on a wall (12) of the liner (10; and welding the insert (22) to the wall. A method according to claim 1, further comprising the step of filament winding the liner (10), said filaments capturing the fitting against the wall. A method according to claim 1 or 2, further comprising the step of cutting a hole through the wall (12) of the liner (10) inside the fitting (14) to create a passage through the fitting and the liner wall. A method according to claim 2, wherein the fitting (14) defines a passage (18) therethrough, and said insert (22) is installed in the passage. A method according to claim 4, wherein the insert (22) has a flange (26) that is engaged with the fitting (14) to retain the fitting on the liner (10). A method according to claim 4 or 5, wherein the passage (18) is placed communication with an interior of the liner (10) through the hole. A method according to claim 1, wherein the insert (22) is engaged with the fitting (14) to retain the fitting on the lines (10). A method according to any one of the preceding claims, wherein the liner (10) and insert (22) are made of materials having substantially similar melting temperatures and the step of welding includes heating an area of the liner and insert to about the same temperature. A method according to any one of claims 1 to 7, wherein the liner (10) and insert (22) are made of materials having substantially different melting temperatures and the step of welding includes heating an area of the liner (10) and insert (22) to different temperatures. A method according to any one of the preceding claims, wherein the liner (10) and insert (22) are made of plastic. A method according to any one of the preceding claims, wherein the liner (10) is generally cylindrical. A method according to claim 11, wherein the fitting (14) is installed on a generally cylindrical side wall (12) of the liner. A method according to any one of the preceding claims, wherein the step of welding includes heating the insert (22) and an area of the liner (10) and pressing the insert into the liner to bond therewith. A method of manufacturing a fluid-containing vessel having a fitting, comprising the steps of: forming a liner (10) defining the vessel; providing a preformed fitting (14) having a flange (16); installing an insert (22) having a flange (26) in the fitting (14), said insert flange (26) engaging the fitting (14); positioning the fitting (14) on a wall (12) of the liner (10) and welding the insert (22) to the wall, the insert flange (26) retaining the fitting to firmly secure the fitting on the liner and bond it therewith; filament winding the liner (10), said filaments capturing the fitting flange (16) against the wall; and cutting a hole through the wall (12) of the liner (10) inside the fitting (14) to create a port through the fitting. A method of manufacturing a fluid-containing vessel having a port, comprising the steps of: rotationally molding a liner (10) of plastic material having a generally cylindrical shape; providing a preformed fitting (14) having a flange (16) and a passage therethrough; installing an insert (22) of the same material as the liner (10) in the passage of the fitting (14), said insert having a flange (26) engaging the fitting; heating the insert (22) and an area of a cylindrical wall (12) of the liner (10) where the fitting is to be installed to soften the insert and the area of the wall; locating the flange (16) of the fitting on the area of the wall and pressing the insert (22) into the area so as to bond the insert to the wall, the insert flange (26) retaining the fitting to firmly secure the fitting on the liner and bond it therewith; filament winding the liner, said filaments capturing the fitting flange (16) against the wall; and cutting a hole through the wall of the liner (10) inside the fitting to create a port through the passage. An apparatus for installing a fitting (14) on a molded vessel liner (10), comprising: means for supporting the fitting (14) and an insert (22) near the liner; a heater (48); means (50) for positioning the heater between the fitting (14) and the liner (10) for heating the insert (22) and an area of the liner; and means (34,38) for positioning the fitting (14) on the liner and pressing the insert into the liner to weld the insert to the liner, characterised in that the insert (22) comprises means (26) for engaging the fitting (14) to firmly secure the fitting on the liner and bond it therewith. An apparatus according to claim 16, further comprising means (54) for removing material of the liner to place an interior of the vessel in communication with the fitting. An apparatus according to claim 16 or 17, wherein the means for supporting the fitting (14) and insert (22) and the means for positioning the fitting (14) comprises a movable mounting head (34). An apparatus according to claim 18, further comprising a powered driver (38) for moving the mounting head (34). An apparatus according to any one of claims 16 to 19, wherein the heater (48) comprises a two sided heat mirror. An apparatus according to claim 20, wherein the two sides of the heat mirror are separately controllable. An apparatus according to any one of claims 16 to 21, wherein the means (50) for positioning the heater (48) comprises a support arm on which the heater is pivotably mounted. An apparatus for installing a fitting (14) on a molded vessel liner (10), comprising: a platform (32); a mounting head (34) movably mounted on the platform and adapted for supporting the fitting (14) and an insert (22) the insert comprising means (26) for engaging the fitting (14) to firmly secure the fitting on the liner and bond it therewith, near the liner, positioning the fitting on the liner, and pressing the insert into the liner; a driver (38) adapted to move the mounting head (34); a heat mirror (48) movably mounted on the platform; and a support arm (50) having the heat mirror pivotably mounted thereon and adapted for positioning the heater between the fitting and the liner.

Inventors: GOODGE KEVIN, HLEBOVY JIM, MURPHY JAMES C, GOODGE, KEVIN, HLEBOVY, JIM, MURPHY, JAMES C.
Applicants: ESSEF CORP, ESSEF CORPORATION
Application year: 1996
Main classification: B29D22
IPC codes: B29C33, B29C65, B29C53, B29C70