Title of Invention

ELECTRICAL WATER HEATER WITH ELECTRIC SHOCK PROTECTION

Abstract

The present invention relates to a safeguard technology for an electrical water heater and provides an electrical water heater with electric-shock protection. The electrical water heater with electric-shock protection includes an outer casing, an inner tube, an electrical heater, an inlet pipe, an outlet pipe and an inlet lining pipe and an outlet lining pipe. The inlet lining pipe and the outlet lining pipe are insulating pipes. The pipe bodies of said inlet and outlet lining pipes can be disposed outside the inner tube or disposed inside a cavity of inner tube. The inlet lining pipe or the outlet lining pipe are configured in such a manner that they are wound in a shape of folded lines or curved lines or in a shape of "M" or inverted "U", or in a combination form that a sleeve pipe is fitted over said inlet linear pipe so that the length of water flow passage is increased. Further, the length (L) between an inlet port of the inlet lining pipe and an outlet port of the outlet lining pipe satisfies the following expression: L>53 r2 which defines a safety requirement for the electrical water heater. With this construction, the occurrence of electrical leakage of the electrical water heater is prevented.

Full Text

ELECTRICAL WATER HEATER WITH ELECTRIC-SHOCK PROTECTION Field of the Invention The present invention relates to a safeguard technology for an electrical water heater, and more particularly, to an electrical water heater with electric-shock protection. Description of the Related Art There are two types of methods for preventing an electric shock in the conventional electrical water heater, one is provided with an electrical leakage switch which automatically disconnects the electrical water heater from the power supply when the leakage current goes beyond a predetermined value so as to insure the electrical water heater in safe and reliable operation, the other is provided with an automatic detecting device which automatically detects a leakage current. The automatic detecting device shall automatically send out an alarm when the detected leakage current goes beyond a predetermined value in order to make the user turn off the power supply so that the life safety for the user of the electrical water heater is ensured. However, the safety for the user is strongly relied on the above mentioned electric-shock preventing devices in regard to the above two safe-guard measures. Once the electrical leakage switch or the alarming apparatus of the automatic detecting device is damaged or fails to work properly while an electrical leakage occurs, an accident may take place, thus causing danger to the life of the user of the electrical water heater. This is a potential problem which is involved in the conventional electrical water heater. In fact, the safety assurance of the electrical water heater is most concerned for the user of the electrical water heater, which is also what the manufacturer of the electrical water heater is concerned. In order to ensure the safety for the user of the electrical water heater, the manufacturers of the electrical water heaters have done much research work and got some improvement on it. However, the electrical water heater with these modifications is greatly increased at cost. Further, once the insulating materials are damaged, an electrical leakage shall occur, thus leading to an accident of electric shock. Therefore, the above problem is necessary to be solved to provide an electrical water heater with electric-shock protection and reliable safety assurance at lower cost. SUMMARY OF THE INVENTION The present invention has been made to overcome the above mentioned disadvantages in the prior art. Accordingly, it is an object of the present invention to provide an electrical water heater with electric-shock protection and reliable safety assurance and industrial utility at lower cost. Additional aspects and advantages of the invention will be set forth in part in the description that follows, and in part, will be obvious from the description, or may be learned by the practice of the invention. The forgoing and other aspects of the present invention are achieved by providing an electrical water heater with electric-shock protection, comprising: an outer casing, an inner tube, an electrical heater, an inlet pipe, an outlet pipe. The electrical water heater further includes an inlet lining pipe and an outlet lining pipe, wherein both the inlet lining pipe and the outlet lining pipe are insulating pipes. Preferably, pipe bodies of the inlet lining pipe and the outlet lining pipe are provided inside the electrical water heater, and the inlet lining pipe and the outlet lining pipe are connected to an inlet pipe and an outlet pipe of the outer casing, respectively. Preferably, pipe bodies of the inlet lining pipe and the outlet lining pipe are provided outside the inner tube, and the inlet lining pipe and the outlet lining pipe are connected to an inlet pipe and an outlet pipe of the inner tube, respectively. Preferably, pipe bodies of the inlet lining pipe and the outlet lining pipe are provided inside a cavity of the inner tube. Preferably, the electrical water heater further comprises a decorative cover, the decorative cover is disposed outside of the inlet pipe and the outlet pipe of are provided inside a cavity defined by the outer casing and the decorative cover, wherein the inlet lining pip e and the outlet lining pipe are connected to inside ends of the inlet threaded nozzle and the outlet threaded nozzle of the decorative cover, respectively. Preferably, the inlet lining pipe and the outlet lining pipe disposed inside the inner tube are configured to have a shape selected from the group consisting of: a linear pipe, a spiral pipe, a U-shaped pipe, a M-shaped pipe, a curved pipe or a combination of a linear pipe and a sleeve pipe. Preferably, the linear pipe and the sleeve pipe are integrally formed, a pipe section of the linear pipe disposed inside the inner tube is provided inside the sleeve pipe, the linear pipe and the sleeve pipe are concentric with each other, the linear pipe and the sleeve pipe are integrally connected to each other at the top ends thereof, a through hole is opened at the pipe wall of the linear pipe close to the top of the linear pipe, a gap defined between the inlet lining pipe and the sleeve pipe is configured to be a water flow passage, an outlet port provided on a lower end of the sleeve pipe communicates with the inner tube, and the linear pipe and the sleeve pipe are insulating pipes made of insulating materials. Preferably, the linear pipe and the sleeve pipe are separately formed, the sleeve pipe are fitted over the pipe section of the linear pipe disposed inside the inner tube, the linear pipe and the sleeve pipe are concentric with each other and are fixed by a fastening member at the top end engagement surfaces of the sleeve pipe and the linear pipe. Preferably, the fastening member includes a bolt and a nut, a heat melting screw or a self-tightening screw or the like; alternatively, the inlet and outlet linear pipes and the sleeve pipe are fixed at the top end engagement surfaces thereof by a bolt and a nut or a heat melting screw or a self-tightening screw. Preferably, peripheral edges of the lower ends of the inlet and outlet lining pipes where the inlet and outlet lining pipes engage with the inlet and outlet pipe are provided with threads so as to engage with threads provided on inside walls of the inlet and outlet pipes. Preferably, outer peripheral surfaces of the lower ends of the inlet and outlet lining pipes engage with inner walls of the inlet and outlet pipes in such manner that a male member is snapped into a female member. Preferably, walls of lower nozzles of the inlet and outlet pipes where the inlet and outlet lining pipes engage with the inlet and outlet pipes are provided with a protruding round disk at which the inlet and outlet lining pipes are fixed by engaging a screw cap with male threads on the inlet and outlet pipe. Preferably, inside walls of the inlet and outlet pipes and the linear pipe and the sleeve pipe are made of insulating materials. Preferably, a length L between an inlet port of the inlet lining pipe and an outlet port of said outlet lining pipe satisfies the following expression: L>53 r2, wherein r designates the radium of the inner hole of the inlet and outlet pipes. According to specific experiments and the stipulations of the National Product Standards GB13955-92 (the Assembly and Operation of the Electrical Leakage Protector), the leakage current is required to be not more than 10 mA so that safety for the user of an electrical water heater is guaranteed. When a current leakage occurs in the inner tube or a voltage of 220 V is directly applied to the heater being heated, the dielectric resistance of water (R) is set to be 22X103 Ω (R=220V/10mA). As specific resistance P of water is 1300 Ω • cm, if the length of the insulating pipe is set to be L, and the radium of an inner hole of the insulating pipe is set to be r, the dielectric resistance is set to be R, and the specific resistance of water is set to be P , then the length L of the insulating pipe is determined by the following expression: (Equation Removed) Therefore, when the length (L) of the insulating pipe is set to be greater than 53 times of square radium (r) of the inner hole, i.e. L>53 r2 it is possible to make water serve as insulating substance by virtue of the resistance of water. The present invention has been made to meet the requirements for the length of the insulating pipe for safety assurance by the ways of making use of the internal space of the electrical water heater. In order to achieve the above objects, the electrical water heater of the present invention is configured in such a manner that the insulating pipe is provided outside of the outer casing or the inner tube, or is provided in an interlayer space or a cavity of the inner tube. Further, the insulating pipes are wound in a shape of folded line or curved line, or be formed into U-shaped pipe, a M-shaped pipe, or a combination of a linear pipe and a sleeve pipe so that the length of water flow passage is increased. In this way, the requirements for the length of the insulating pipe for safety assurance are satisfied without occupancy of external space of the electrical water heater. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and advantages of the invention will become apparent and readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings, in which: Fig 1 is a schematic view of the assembling configuration of the inlet and outlet lining pipe of the electrical water heater with electric-shock protection according to a first embodiment of present invention; Fig 2 is a schematic view of the assembling configuration of the inlet and outlet pipe of the electrical water heater with electric-shock protection according to a second embodiment of present invention, in which the inlet and outlet lining pipe are provided inside the electrical water heater; Fig 3 is a cross-sectional view showing the assembling configuration of a linear inlet pipe and a sleeve pipe of the electrical water heater with electric-shock protection of the present invention; Fig 4 is a cross-sectional view of the configuration of the inlet lining pipe which are bended into a shape of a rectangular frame according to a third embodiment of the electrical water heater with electric-shock protection of present invention; Fig 5 is a cross-sectional view of the configuration of the inlet lining pipe which are bended into a shape of "M" according to a fourth embodiment of the electrical water heater with electric-shock protection of present invention; Fig 6 is a cross-sectional view of the configuration of the inlet lining pipe which are bended into a shape of inverted "U" according to a fifth embodiment of the electrical water heater with electric-shock protection of the present invention; Fig 7 is a schematic view showing the outlet lining pipe provided on internal tube according to a sixth embodiment of the electrical water heater with electric-shock protection of the present invention, in which the outlet lining pipe is configured into a horizontal sleeve pipe; Fig 8 is a schematic view showing an inlet lining pipe according to a seventh embodiment of the electrical water heater with electric-shock protection of the present invention, in which the inlet lining pipe is configured to be a sleeve pipe and the outlet lining pipe is bended into a shape of "N"; and Fig 9 is a schematic view showing an inlet lining pipe and an outlet lining pipe according to an eighth embodiment of the electrical water heater with electric-shock protection of the present invention, in which both the inlet lining pipe and the outlet lining pipe are configured to be sleeve pipe. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described hereinafter in detail with reference to the attached drawings, in which the like reference numerals refer to the like elements throughout the specification. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein; rather, this embodiment is provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Fig 1 shows an electrical water heater with electric-shock protection according to a first embodiment of the present invention. The inlet and outlet lining pipe are installed on an inlet pipe 3 and an outlet pipe 4 of an outer casing 14 respectively. The inlet pipe 3 induced out from an inlet port of the heating inner tube 5 of the electrical water heater 20 extends out from an end of the outer casing 14 and is induced into an inlet lining pipe 1. The outlet pipe 4 induced out from an outlet port of the heating inner tube 5 of the electrical water heater 20 extends out from an end of the outer casing 14 and is induced into an outlet lining pipe 15. The inlet lining pipe 1 and the outlet lining pipe 15 are formed of plastic pipes made from high-temperature-resistant and high-pressure-resistant materials, for example, polytetrafluoroethylene. The inner walls of the inlet lining pipe 1 and the outlet lining pipe 15 may be made of insulating materials. Water is introduced into the inner tube through the following routes. Water is firstly introduced into the lower inlet port of the inlet lining pipe 1 and passes through the inlet lining pipe 1. Next, water is guided into the upper of the inlet pipe 3 and introduced into the inner tube 5. Water is discharged out through water discharging passage as described as follows. Water is discharged into an upper port of the outlet lining pipe 15 from the inner tube 5 via an outlet port of the outlet pipe 4. Then, water is guided to a lower port of the outlet lining pipe 15 via the outlet lining pipe 15. At this point, water is discharged out through a sprinkler. The above mentioned water flow passage is required to satisfy the following condition: L> 53 r2, wherein L designates the length of water flow passage and r designates the radium of the inner hole of the inlet lining pipe 1 or the outlet lining pipe 15. In one example of the electrical water heater of the present invention, the inside diameter of the inlet lining pipe 1 and the outlet lining pipe 15 is configured to be 0.5 cm. Accordingly, the length L of the inlet lining pipe 1 or the outlet lining pipe 15 is calculated based on the above expression. In this case^ the length of the inlet lining pipe 1 or the outlet lining pipe 15 obtained from the above calculation is determined to be longer than 3.32 cm. As a result, if the length of the inlet lining pipe 1 or the outlet lining pipe 15 is configured to be in the range of 3.4-5 cm, an electric-shock protection device with reliable assurance will be achieved. Fig 2 shows an electrical water heater with electric-shock protection according to a second embodiment of the present invention. A decorative cover 21 is installed on a bottom of the outer casing 14 of the electrical water heater 20. The inlet threaded nozzle 22 and the outlet threaded nozzle 23 are installed on the decorative cover 21. The inlet lining pipe 1 and the outlet lining pipe 15 which are connected to the inlet pipe 3 and the outlet pipe 4 of the inner tube 5 respectively are wound in the cavity formed by the outer casing 14 and the decorative 21 in a shape of folded line or curved line. The other end of the inlet lining pipe 1 and the outlet lining pipe 15 are connected to the inner end of the inlet threaded nozzle 22 and the outlet threaded nozzle 23 on the decorative cover 21, respectively. Water is introduced into the inner tube 5 through the following routes. Water is firstly introduced into a lower inlet port of the inlet lining pipe 1 through the inlet threaded nozzle 22 and passes through the inlet lining pipe 1. Then water is guided into the upper of the inlet pipe 3 and introduced into the inner tube 5. Water is discharged out through a water discharging passage as described as follows. Water is firstly introduced into the outlet pipe 4 and then guided into an upper port of the outlet lining pipe 15. Next, water is introduced into a lower port of the outlet lining pipe 15 via the outlet lining pipe 15. Thereafter, water is discharged out through a sprinkler via the outlet threaded nozzle 23. The above mentioned water flow passage is required to satisfy the following condition: L>53 r2, wherein L designates the length of water flow passage and r designates the radium of the inner hole of the inlet lining pipe 1 or the outlet lining pipe 15. With the above construction, the length of water flow passage in folded line is increased, thereby the requirements for safety are satisfied. The inlet lining pipe 1 and the outlet lining pipe 15 are formed of plastic pipes made from high-temperature-resistant and high-pressure-resistant materials, for example, polytetrafluoroethylene. The inner walls of the inlet lining diameter of the inlet lining pipe 1 and the outlet lining pipe 15 is configured to be 0.5 cm. Accordingly, the length of the inlet lining pipe 1 and the outlet lining pipe 15 is calculated based on the above expression. In this case, the length of the inlet lining pipe 1 or the outlet lining pipe 15 obtained by the above calculation is determined to be longer than 3.32 cm. As a result, if the length of the inlet lining pipe 1 and the outlet lining pipe 15 is configured to be in the range of 5-10 cm, an electric-shock preventing device with reliable assurance will be achieved. Referring to Fig 3, the electrical water heater is generally designated by reference numeral 20. In order to overcome the disadvantage that the insulating pipe is exteriorly disposed and to ensure that the expression L>53 r2 is satisfied so as to meet the specific requirements in compliance with the safety standard, the present invention employs the following technical scheme. That is, the inlet lining pipe 1 is configured to be a combination form of a linear pipe and a sleeve pipe 6. More specifically, a sleeve pipe 6 is fitted over a pipe section of the inlet lining pipe 1 disposed inside the inner tube 5. The sleeve pipe 6 and the inlet lining pipe 1 are provided to be concentric with each other. Further, the sleeve pipe 6 and the inlet lining pipe 1 are fixed at the top end engagement surface thereof by a bolt 7 and a nut 11. Alternatively, the bolt 7 and the nut 11 can be omitted, and the inlet lining pipe 1 is fixedly connected to the sleeve pipe 6 in such manner that the threads of the inner wall of the sleeve pipe 6 engage with threads provided on the upper peripheral edge of the inlet lining pipe 1. The inlet lining pipe 1 is provided with a through hole 16 opened at the wall of pipe close to the top portion of pipe. The gap defined between the inlet lining pipe 1 and the sleeve pipe 6 is configured to be a water flow passage 17. An outlet port 18 provided at the lower end of the sleeve pipe 6 communicates with the inner tube 5. A protruding round disk 19 is provided on the wall of a nozzle of the inlet lining pipe 1 where the lower end of the inlet lining pipe 1 engages with the inlet pipe 3. The inlet lining pipe 1 is fixed to its position by engaging a screw cap 2 with male threads provided on the outer peripheral wall of the inlet pipe 3. The inlet lining pipe 1 and the sleeve pipe 6 can be integrally formed. For example, the inlet lining pipe 1 and the sleeve pipe 6 are integrally connected to each other at the top ends thereof and are concentric with each other. In this way, the bolt 7 and the nut 11 are omitted. In this case, the lower end of the inlet lining pipe 1 without the protruding round disk 19 is fixedly connected to the inlet pipe 3 by means of snap-fitting with a female and a male polygon. Alternatively, the lower end of the inlet lining pipe 1 is fixedly connected to the inlet pipe 3 by engaging threads provided on the peripheral edge of the lower end of the inlet lining pipe 1 with threads provided on the inner wall of the inlet pipe 3. The inlet lining pipe 1 and the sleeve pipe 6 are insulating pipes 6 made of insulating materials. The outlet lining pipe 15 is also the insulating pipes made of insulating materials. It should be noted that the above insulating pipes can be configured in such a manner that only the inner wall of the pipes are made of insulating materials. Water is introduced into the inner tube 5 through the following routes. Water is firstly introduced into the lower port of the inlet lining pipe 1 and then passes through the upper through hole 16. Next, water is introduced into the outlet port 18 via the water flow passage 17. Thereafter, water is introduced into the inner tube 5. Water is discharged out through water discharging passage as described as follows. Water is firstly introduced into the upper port of the outlet lining pipe 15 from the inner tube 5. Next, water is guided to the lower port of the outlet lining pipe 15 through the outlet lining pipe 15. Thereafter, water is discharged outside from a sprinkler through a nozzle of the outlet pipe 4. The above mentioned water flow passage is required to satisfy the following condition: L>53 r2, wherein L designates the length of water flow passage and r designates the radium of the inner hole of the inlet lining pipe 1 or the outlet lining pipe 15. With the above construction, the length of the folded line of water the present invention. In order to ensure that the expression L>53 r2 is satisfied, the inlet lining pipe 1 is formed into a shape of rectangular frame. With this construction, the cavity of the inner tube is effectively used while the requirements for the length of the insulating pipe are satisfied. Fig 5 shows an electrical water heater according to a fourth embodiment of the present invention. In the electrical water heater according to a fourth embodiment of the present invention, the inlet lining pipe is configured to be in a shape of "M". Fig 6 shows an electrical water heater according to a fifth embodiment of the present invention. In the electrical water heater according to a fifth embodiment of the present invention, the inlet lining pipe is configured to be in a shape of inverted "U". The outlet lining pipe 15 may be configured to employ the same construction as that of the inlet lining pipe 1 as shown in Figs 5 , 6 and 7 or a construction being slightly modified from the above. Further, the outlet lining pipe 15 may be separately used or used together with the inlet lining pipe 1. Fig 7 shows an electrical water heater according to a sixth embodiment of the present invention. In the electrical water heater according to a sixth embodiment of the present invention, the inlet lining pipe 1 is configured to be in a shape of a "M" or inverted "U" or a rectangular frame, and the outlet lining pipe 15 which is configured to be horizontal combination type sleeve pipe is provided above the inner tube 5. The inlet pipe 3 and the outlet pipe 4 of the electrical water heater are connected to outside lining pipes, respectively. Fig 8 shows an electrical water heater according to a seventh embodiment of the present invention. In the electrical water heater according to a seventh embodiment of the present invention, the inlet lining pipe 1 is configured to be horizontal combination type sleeve pipe, and the outlet lining pipe 15 is formed into a shape of "N". The inlet pipe 3 and the outlet pipe 4 of the electrical water heater are connected to outside lining pipes, respectively. Fig 9 shows an electrical water heater according to an eighth embodiment of the present invention. In the electrical water heater according to an eighth embodiment of the present invention, both the inlet lining pipe 1 and the outlet lining pipe 15 are configured to be horizontal combination type sleeve pipes. The inlet pipe 3 and the outlet pipe 4 of the electrical water heater are connected to outside lining pipes. Alternatively, the inlet pipe 3 and the outlet pipe 4 of the electrical water heater are not connected to outside lining pipes but directly connected to outlet pipe or sprinkler in same manner as that in the conventional electrical water heater. As described in the above embodiments, the length of the inlet lining pipe 1 is increased with a good variety of configuration as illustrated above. However, the configuration of the inlet lining pipe 1 and the outlet lining pipe 15 of the electrical water heater according to present invention is not limited to the above examples. It would be appreciated by those skilled in the art that various changes or modifications may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents. AMENDED CLAIMS I /We claim: 1. An electrical water heater with electric-shock protection, comprising an outer casing, an inner tube, an electrical heater, an inlet pipe, an outlet pipe, an inlet lining pipe and an outlet lining pipe, wherein both said inlet lining pipe and said outlet pipe are insulating pipes and disposed outside said electrical water heater, characterized in that the length between the inlet port of said inlet lining pipe and the outlet port of said outlet lining pipe satisfies the following expression: L>53 r2, wherein r designates the radius of an inner hole of the inlet and outlet pipes, and said inlet lining pipe and said outlet lining pipe optionally disposed within a cavity of said inner tube. 2. The electrical water heater with electric-shock protection according to claim 1, wherein said inlet lining pipe and said outlet lining pipe are formed into a combination of a linear pipe and a sleeve pipe. 3. The electrical water heater with electric-shock protection according to claim 1, comprises a decorative cover, said decorative cover is disposed outside of said inlet pipe and said outlet pipe of said outer casing and is provided with an inlet threaded nozzle and an outlet threaded nozzle; pipe bodies of said inlet lining pipe and said outlet lining pipe are provided inside a cavity defined by said outer casing and said decorative cover, wherein said inlet lining pipe and said outlet lining pipe are connected to an inside end of said inlet threaded nozzle and said outlet threaded nozzle of said decorative cover, respectively. 4. The electrical water heater with electric-shock protection according to claim 2, wherein: said linear pipe and said sleeve pipe are integrally formed, a pipe section of said linear pipe inside said inner tube is provided inside said sleeve pipe, and said linear pipe and said sleeve pipe are concentric with each other, said linear pipe and said sleeve pipe are integrally connected to each other at the top ends thereof, a through hole is opened at a pipe wall of said linear pipe close to the top of the linear pipe, a gap defined between said inlet lining pipe and said sleeve pipe is configured to be a water flow passage, an outlet port provided on a lower end of said sleeve pipe communicates with said inner tube. 5. The electrical water heater with electric-shock protection according to claim 4, wherein: said linear pipe and said sleeve pipe are separately formed, said sleeve pipe is fitted over said pipe section of said linear pipe disposed inside said inner tube, said linear pipe and said sleeve pipe are concentric with each other, and said sleeve pipe and said linear pipe are fixed by a fastening member at the top end engagement surfaces thereof. 6. The electrical water heater with electric-shock protection according to claim 5, wherein: said fastening member includes a bolt and a nut, said inlet or outlet linear pipes and said sleeve pipe are fixed at the top end engagement surface thereof by said bolt and said nut. 7. The electrical water heater with electric-shock protection according to claim 1 or 2 or 4, wherein: peripheral edges of the lower ends of said inlet and outlet lining pipes where said inlet and outlet lining pipes engage with said inlet and outlet pipes are provided with threads in order to engage with threads provided on an inside wall of said inlet and outlet pipes. 8. The electrical water heater with electric-shock protection according to claim 1 or 2 or 4, wherein: outer peripheral surfaces of the lower end of said inlet and outlet lining pipes engage with inner walls of said inlet and outlet pipes in such manner that a male member is snapped into a female member. 9. The electrical water heater with electric-shock protection according to claim 5, wherein: a wall of a lower end of a nozzle of said inlet and outlet pipes where said inlet and outlet pipes engage with said inlet and outlet pipes is provided with a protruding round disk at which said inlet and outlet lining pipes are fixed by engaging a screw cap with male threads on said inlet and outlet pipes. 10. The electrical water heater with electric-shock protection according to claim 1 or 2, wherein: inside walls of said inlet and outlet pipes, said linear pipe and said sleeve pipe are made of insulating materials.

Documents:

1584-delnp-2004-abstract.pdf

1584-delnp-2004-claims cancelled.pdf

1584-delnp-2004-claims.pdf

1584-delnp-2004-complete specification (granted).pdf

1584-delnp-2004-correspondence-others.pdf

1584-delnp-2004-correspondence-po.pdf

1584-delnp-2004-description (complete).pdf

1584-delnp-2004-drawings.pdf

1584-delnp-2004-form-1.pdf

1584-delnp-2004-form-19.pdf

1584-delnp-2004-form-2.pdf

1584-delnp-2004-form-26.pdf

1584-delnp-2004-form-3.pdf

1584-delnp-2004-form-5.pdf