AN INSULATED PIPE FOR GASEOUS MEDIA AND A METHOD OF MANUFACTURING SAID PIPE

Abstract: An insulated pipe for gaseous media of a low overpressure, particularly a duct for air-conditioning systems, is made of one piece (4) of polyurethane foam. The inner surface of the pipe is provided with a tight plastic film (2). Such a pipe is easy to assemble with other pipes of the same type since the pipes can be glued together at their end surfaces. Such a pipe furthermore eliminates to a substantial extend energy losses and noise nuisances deriving from gas flowing in the pipe. A method of manufacturing the pipe includes the steps of casting said pipe in a mould comprising two mould halves (6, 7), a core being centrally located in said mould. Prior to the closing of the mould, a detaching agent is applied onto the inner surface of the mould halves (6, 7) and onto the core, said core furthermore being coated with a plastic film. Subsequently, liquid polyurethane is fed to the mould through two opposing nozzles in the mould halves (6, 7). Upon curing the mould is opened and the cast, completed pipe is then released from the core.

Description: Title: An Insulated Pipe for Gaseous Media and a Method of Manufacturing said Pipe Technical Fiel The invention relates to an insulated pipe for gaseous media of a low overpressure, particularly for air-con¬ ditioning systems. Background Art DE-OS No. 2,003,139 discloses an insulated pipe of the above type and which comprises at least two pipe members interconnected by means of key and tongue connections along joint faces extending along the longitudinal direc¬ tion of the- pipe, which complicates the assembling of a complete pipe cross section. The known pipe is further¬ more encumbered with the draw-back that when manufacturing a duct comprising two or more pipes it is difficult to assemble the pipes two and two since a particular connect¬ ing member is necessary when assembling two pipes end to end, said connecting member inter alia engaging particular keys at the ends of the pipes. These connecting members imply that the inner surface of the pipes are not smooth at these connecting members whereby whirls occur in the gas. As a result, energy losses and noise nuisances un- desired particularly at air-conditioning systems in dwell¬ ing houses arise. Disclosure of Invention The object of the invention is to provide an insulated pipe of the type mentioned above, which is easy to assem¬ ble with other pipes of the same type,- and which elimi¬ nates to a substantial extent the energy losses and noise nuisances deriving from gas flowing in the pipe. The insulated pipe according to the invention is charac¬ terised in that the pipe is made of one piece of poly= urethane foam, and that the inner surface of the pipe is provided with a tight plastic film. Two pipes of this type are easy to assemble since said pipes may be glued togeth¬ er at their end surfaces without necessitating particular connecting members and particular keys or the like members at the ends of the pipes. Furthermore the inner surface of the pipes is smooth at the connecting members and conse- quently no whirls occur in the gas. As a result the energy losses and the noise nuisances deriving from gas flowing in the pipes are avoided. The tight plastic film implies partly that the gas flowing in the pipe does not diffuse out and partly that the inner surface of the pipe wall is smooth in such a manner that the friction between the pipe and the flowing gas is relatively inferior, whereby energy losses and noise nuisances deriving from flowing gas are avoided to a substantial extent. The plastic film may according to the invention be a poly= vinyl chloride film. Such a film is easily detached from the inner core within the mould used by the manufacture of the pipe when said pipe is removed from the mould, and furthermore said film ensures a smooth, tight inner sur¬ face. The plastic film may according to the invention also be a polyethylene film, whereby a particularly inexpensive pipe is obtained. Furthermore according to the invention the pipe may ex¬ teriorly be of a quadrangular cross section. As a result, the pipe comprises planar surfaces which individually form a reliable contact surface permitting gluing of the pipe onto a ceiling or a wall without the use of clamps or the like securing means. G./I?I IfO The invention also relates to a method of manufacturing insulated pipes of the type mentioned above. This method is characterised in that the pipe is manufactured through casting in a substantially horizontal mould comprising two mould halves forming a mould chamber, as well as a core centrally located in said mould chamber, a detaching agent being applied before the mould is closed onto the inner surface of the mould halves and onto the outside of the core, said core being coated with a plastic film, whereafter liquid polyurethane is fed to the mould through two opposing nozzles in the mould halves and the mould is opened upon curing by means of two opposing air cylinders connected to the mould halves, the cast pipe subsequently being released from the core. In this manner a simple and inexpensive method of manufacturing the pipe is provided. Brief Description of Drawings The invention will be described below with reference to the accompanying drawings, in which Fig. 1 is an axially sectional view through part of an embodiment of an insulated pipe according to the inven¬ tion in the form of a straight pipe section. Fig. 2 is a cross-sectional view through the pipe of Fig. 1, Fig. 3 is a cross-sectional view through a second embodi- ment of the pipe according to the invention in the form of a 90 elbow of a pipe section. Fig. 4 is a cross-sectional view through a third embodi¬ ment of the pipe according to the invention in the form of a 45° elbow of a pipe section, Fig. 5 is a cross-sectional view through a fourth embodi- OMPI ment of the pipe according to the invention in the form of a pipe section comprising a 90 branch , Fig. 6 is a cross-sectional view through a fifth embodi¬ ment of the pipe according to the invention in the form of a pipe section comprising a 45 branch. Fig. 7 is a cross-sectional view through a seventh embo¬ diment of the pipe according to the invention in the form of a pipe section comprising a narrowing. Fig. 8 is a perspective view of a first embodiment of a mould for use by the manufacture of an insulated pipe according to the invention. Fig. 9 is a sectional view taken along the line IX-IX of Fig. 8, whereby the core of the mould is of a circular cross section, and Fig. 10 is a similar sectional view through a second em¬ bodiment of. the mould including a core rectangular in cross section. Best Mode for Carrying Out the Invention The insulated pipe illustrated in Figs. 1 and 2 comprises in the middle a flow duct 1, in which gaseous media of a low overpressure may flow. The pipe is particularly suit¬ able as a duct for air-conditioning systems. The flow duct 1 may be of a circular cross section, cf. Fig. 2, but it may also be of a rectangular or any other suitable cross section. The pipe is made of one piece of polyurethane foam, cf. Fig. 2, and the inner surface of the pipe is provided with a tight plastic film 2. Two such pipes are easy to assem¬ ble since the pipes can be glued directly at their end R-iAC surfaces- 3 without necessitating particular connecting members and keys or the like means at the ends of the pipes. In addition, the connecting members on the inner surface of the pipes are smooth and consequently they imply no whirls in the gas, whereby energy losses and noise nuisances are substantially avoided. The tight plas¬ tic film 2 implies partly that the gas flowing in the flow duct 1 does not diffuse through the wall 4 of the pipe, and partly that a smooth inner surface of said wall 4 of the pipe is provided whereby the friction between the pipe and the flowing gas is relatively inferior. As a re¬ sult, energy losses and noise nuisances are avoided to a substantial extent. The plastic film 2 may be a polyvinyl chloride film. Such a polyvinyl chloride film provides a smooth, tight inner surface of the pipe wall and consequently energy losses and noise nuisances are substantially prevented. In addi¬ tion such a film facilitates the manufacture of the pipe since it is easily detachable from the inner core in the mould used by the manufacture of the pipe when said pipe is removed from the mould, A polyethylene film is also suitable as plastic film, and such a film permits the manufacture of a particularly in¬ expensive pipe. Exteriorly the embodiment of the pipe illustrated in Figs. 1 and 2 is of a quadrangular cross section. As a result, the pipe comprises planar surfaces 5 individually forming a reliable contact surface which permits a gluing of the pipe onto a ceiling or a wall without the use of clamps or the like securing means. Conduits comprising elbows f branches, narrowings and the like such as for instance ducts for air-conditioning sys¬ tems in dwelling houses are constructed partly of straight , pipe sections, cf. Figs, 1 and 2, and partly special pipe sections, cf. Figs, 3-7. Figs. 3 and 4 illustrate pipe sections comprising a 90° and a 45°, respectively, elbow, whereas Figs. 5 and 6 illustrate pipe sections with a 90 and a 45°, respectively, branch. Fig. 7 illustrates a pipe section comprising a narrowing. The pipe sections of Figs. 3-7 are constructed in the same manner as the pipe section of Figs. 1 and 2, i.e. each section is made of one piece of polyurethane foam and the inner surface of each section is provided with a tight plastic film. Fig. 8 illustrates an embodiment of a mould for use by the manufacture of insulated pipes. The mould comprises a low¬ er mould half 6 and an upper mould half 7, said halves together defining a chamber, as well as a core 8, cf. Fig. 9, centrally located in said chamber. The two mould halves 6 and 7 are interconnected at one end by means of a hinge joint 9. At the opposite end of the mould a joint 10 is secured on the underside of the lower mould half 6, and a similar joint 11 is mounted on the top side of the upper mould half 7 opposite the joint 10, said joints 10 and 11 individually being connected to an air cylinder not shown for opening and closing the mould. In addition, the lower mould half 6 and the upper mould half 7 are individually provided with a nozzle 12 and 13, respectively, through which liquid polyurethane may be fed. Each nozzle 12 and 13 is provided with a filler stub with snap coupling not shown. The manufacture of an insulated pipe is carried out by casting in the mould described in Figs. 8 and 9 in the following manner. Before the mould is closed, a detaching agent is applied onto the inner surface of the mould halves 6 and 7 and onto the core 8, whereafter the core 8 is coated with the plastic film. Subsequently, the mould is closed, the air cylinders moving the mould halves 6 and 7 towards each other. Then liquid polyurethane is fed to G: Γ _ the mould through the nozzles 12 and 13 in the mould halves 6 and 7, Upon curing, the mould is opened again, the two. air cylinders moving the mould halves 6 and 7 away from each other, and subsequently the pipe can be removed from the core 8. This method is simple and inex¬ pensive for manufacturing pipes, but any other suitable method may be employed too. Fig. 10 illustrates, as Fig. 9, a cross-sectional view through a second embodiment of the mould, said mould com- prising a core 8a of a rectangular cross section. The pipe produced by means of the mould of Fig. 10 comprises thus a rectangular flow duct. The core 8 may have any other suit¬ able shape beyond the circular and quadrangular cross sec¬ tion. When manufacturing pipes with varying dimensions of the flow duct, it is often sufficient to use the same mould halves 6 and 7 and merely to replace the core 8 by another core having the desired cross-sectional dimension. When manufacturing pipes in the form of straight pipe sec¬ tions, the core 8 or '8a is preferably made of one piece, whereas when manufacturing particular pipe sections such as for instance the pipe sections illustrated in Figs. 3-7, cores are preferably used, the cross section of which is constructed of two or more parts. So as to permit the completed pipe to be easily detachable from the core 8 when the pipe is completely cast in the mould, the core 8 may be primed with a polyamide-coating (3) of the type Rilsan . OI .PI

Claims: * Ct 1laims ' : 1. An insulated pipe for gaseous media of a low over¬ pressure, particularly a duct for air-conditioning systems, c h a r a c t e r i s e d in that the pipe is made of one piece (4) of polyurethane foam, and that the inner surface of the pipe is provided with a tight plastic film (2) . 2. An insulated pipe as claimed in claim 1, c h a r ¬ a c t e r i s e d in that the plastic film (2) is a poly= vinyl chloride film. 3. An insulated pipe as claimed in claim 1, c h a r ¬ a c t e r i s e d in that the plastic film (2) is a poly= ethylene film. 4. An insulated pipe as claimed in claim 1, 2 or 3, c h a r a c t e r i s e d in that exteriorly the pipe is of a quadrangular cross section. 5. A method of manufacturing insulated pipes as claimed in any of the preceding claims 1 to 4, c h a r a c t e r ¬ i s e d in that the pipe is manufactured through casting in a substantially horizontal mould comprising two mould halves (6, 7) forming a mould chamber, as well as a core (8; 8a.) centrally located in said mould chamber, a detach¬ ing agent being applied before the mould is closed onto the inner surface of the mould halves (6, 7) and onto the outside of the core (8; 8a_) , said core being coated with a plastic film, whereafter liquid polyurethane is fed to the mould through two opposing nozzles (12, 13) in the mould halves (6, 7) and the mould is opened upon curing by means of two opposing air cylinders connected to the mould halves (6, 7), the cast pipe subsequently being re- leased from the core (8? 8al ,

Inventors: VIUFF CARL-JOHAN KOFOD FINNEMA, VIUFF, CARL-JOHAN, KOFOD, FINNEMANN
Applicants: VIUFF CARL JOHAN KOFOD FINNEMA, VIUFF, CARL-JOHAN, KOFOD, FINNEMANN
Application year: 1983
Main classification: F16L59
IPC codes: F16L59