NL8902487A - Rust-resistant support for use in agriculture and fishing industry - comprises metal pipe and two plastic resin end stoppers having plastic covering pipe - Google Patents

Abstract

Rust-resistant support is partic. used in agriculture and the fishing industry, and comprises a metal pipe, into whose two ends stoppers are inserted, of plastic resin with an external portion whose external dia. is equal to that of the pipe. A further pipe of plastic resin compatible with that used for the stoppers, fully encloses the first pipe on the outside and also the external portions of the stoppers, being in close contact with both. There can be an annular rib on the outside of the plastic pipe, adhering solidly to it and of the same material, or alternatively >=1 ribs running in the axial direction, and incorporating a number of recesses.

Description

SUPPORT TUBE AND METHOD FOR MANUFACTURING THE SAME

The invention relates to a support tube consisting of an inner tube of metal and an outer casing of plastic.

Such a support tube, in particular for crops, is known from West German utility model 1,834,280. Although the known support tube is provided with seals at the ends, which protect the interior of the inner metal tube from corrosion and stiffen the end edges of the support tube, it is completely unstiffened between the ends, so that the strength thereof is not optimal.

The aim is to overcome this drawback of the known support tube and for this purpose the support tube according to the present invention is provided in combination with plugs arranged on the ends and with stiffeners arranged between the plugs.

The realization of this comprises two embodiments, one embodiment of which is that the stiffeners consist of stiffening rings, which have a reinforcing rounding function, and furthermore, that the stiffening rings on the casing are formed from the same lining material, and the other embodiment thus, the stiffeners consist of longitudinal ribs, which have a reinforcing function which promotes bending strength, and which are preferably constructed in such a way that the longitudinal ribs are of a longitudinal direction and each consist of a series of crenellated studs separated by recesses, which provides more support on the support tube, especially for climbing plants.

It is pointed out that French patent specification 2 168 242 discloses a support tube which is provided with rounded rings, but not in combination with end plugs, with which an overall stiffening of the support tube can be obtained for its good bending-resistant shape retention. as intended now.

The invention further relates to a method of manufacturing a support tube as proposed herein.

The inventor has conducted a number of experiments to establish an effective method of forming a support tube, wherein a synthetic resin plug is sealingly fitted into each of the ends of a metal pipe, and the resulting end-plugged pipe is coated with a resin tube to form the support tube. As a result of these experiments, it has been determined that the most suitable method is one in which the metal pipes and the resin plugs are arranged alternately in succession such that the stop center line is aligned with the pipe center line, the pipes and plugs are interconnected to form a cohesive assembly, which is then fed into a die mounted on an extruder, from which a resin tube is extruded around the cohesive assembly, thereby coating this cohesive assembly with the resin tube. It has further been found that it is desirable to cut the resulting coated cohesive assembly precisely at the location where the resin stop occurs in the coated composite assembly. The invention has been completed on the basis of this finding.

According to one aspect of the invention, there is provided a method of manufacturing a support tube, which consists of extracting metal pipes one by one from their stack of metal pipes, wherein all pipes with their longitudinal centers are parallel to each other and to a passage, withdrawing resin plugs one by one from a stock of resin plugs stored in a location transverse to the passage, placing the pipe in the passage and the stop coinciding with their centerlines, intermittently transferring the pipe in its axial direction to insert the plug into the interstices between the pipes, inserting each end of the plug into corresponding ends of the adjacent pipes in front of and behind it to form a cohesive unit with an even outer diameter, feeding the cohesive unit in a cross-head die.

mounted on an extruder, continuously coating the cohesive assembly with a synthetic resin, and cutting the cohesive assembly thus coated at the portion where the plug occurs.

The invention will be explained in more detail below with reference to illustrative embodiments thereof shown in the drawings.

Pig. 1 is a partly sectional perspective view of a support tube according to the invention.

Fig. 2 is a perspective view of a support tube provided with a number of annular projections.

Fig. 3 is a perspective view of a support tube provided with a number of rectilinear projections. Fig.

4 is a perspective view of a support tube having a conical end.

Fig. 5 is a perspective view of a support tube whose ends are cut at an angle.

Fig. 6 is a schematic perspective view of an apparatus for carrying out one method according to the invention.

Fig. 7 is a schematic perspective view of a position sensing and cutting device according to the invention.

Fig. 8 is a schematic perspective view of a cooling device according to the invention.

Fig. 9 is a schematic perspective view of a crosshead die according to the invention.

Fig. 10 is a schematic perspective view of a device according to the invention for filing the ends of a support tube.

Fig. 11a-b are schematic side views of the successive operations of a method according to the invention.

A description of preferred embodiments of the support tube according to the invention follows.

More particularly, Figure 1 shows a perspective view of a support tube partially cut away for the purpose of showing its internal shape, none of its ends being pointed. As seen in Fig. 1, the support tube comprises a metal pipe 1, synthetic resin plugs 2, one of which is inserted into each end of the metal pipe 1 to form a closed hollow article with an even outer diameter, and a casing 3 of synthetic resin in close contact with the hollow article. Each plug 2 has a smaller diameter portion 12 at one end thereof, which is inserted and closely contacts the inner wall of the metal pipe 1. The plug 2 is joined at the end of the metal pipe by inserting the portion 12 in the metal pipe 1. The remainder of the plug 2, ie the entire plug except for the part 12, has an outer diameter equal to that of the metal pipe 1. Thus, when the plugs 2 are at both ends of the metal pipe 1 to form the closed hollow article, the article has a uniform outer diameter, and when the article is coated with the resin tube 3, the resin tube 3 is in close contact with both the metal pipe 1 and the plug 2 about a flat outer surface without the formation of any discontinuity at the junction between the metal pipe 1 and the plug 2.

The metal pipe 1 preferably has a length between 900 and 4000 mm, an outer diameter between 7 and 40 mm and a thickness between 0.3 and 0.8 mm. most preferably, the length is about 2000 mm, the outer diameter is between 16 and 24 mm, and the thickness is about 0.4 mm. The metal pipe 1 is preferably made of iron. The metal pipe 1 can also be made of copper, aluminum, duraluminium, brass, stainless steel, etc. Furthermore, the metal pipe 1 is not limited to an annular cross-section pipe, but can also be of polygonal or elliptical shape.

The plug 2 is preferably formed of a resin, which must be compatible with the resin forming the casing 3. In this case, when the resin tube 3 is extruded around the plug 2, the tube 3 comes into close contact with the plug 2 to form a unitary product. Preferably, use is made of homopolymers or copolymers containing a resin-compatible monomer. In particular, polyvinyl chloride, polypropylene, polyethylene, ethylene-vinyl chloride copolymer, acrylic butadiene styrene resin, cellulose resin, polyamide, polystyrene and the like can be used for the resin. The plug 2 is preferably provided with the portion 12, which has an outer diameter which is just twice the thickness of the metal pipe 1 smaller than the outer diameter of the metal pipe 1. The portion 12 is preferably made with a small taper to to facilitate insertion into the tube. The smaller diameter portion 12 preferably has an axial length ranging from one to several centimeters, and the plug 2, with the exception of the smaller diameter portion 12, also has an axial length ranging from one to several centimeters varies. The plug 2 is preferably provided with a larger diameter portion in the center thereof and two smaller diameter portions 12 on either side of the larger diameter portion. The larger diameter portion has an axial length of about 3 cm and the smaller diameter portions each have an axial length of about 2 cm, so the total axial length of the plug is about 7 cm. The resin tube 3 must have a have a thickness of more than one-tenth mm, and the thickness is preferably between 0.3 and 1 mm,

Fig. 2 shows a support tube provided with a number of annular protrusions on the outer surface of the resin tube 3. In FIG. 2, the protrusions formed on the outer surface of the resin tube 3 are indicated by 13. The protrusions 13 have an annular shape and are set perpendicular to the longitudinal axis of the resin tube 3. The protrusions 13 are made of a resin similar to the resin of the resin tube 3, and are molded onto the resin tube 3 to form a unitary construction. The annular projections 13 are preferably spaced apart at a distance of 10 or more centimeters. Furthermore, the annular projections 13 are preferably designed with an annular cross-sectional shape and a height between one and several millimeters.

Fig. 3 shows a support tube provided with several rectilinear protrusions 14 on the outer surface of the resin tube 3. The rectilinear protrusions 14 are formed in six rows which extend in the axial direction of the support tube. Each of the rectilinear protrusions includes a number of small protrusions which are separated from the support tube in the axial direction. The protrusions 14 are formed of a resin material similar to the resin material forming the tube 3, and the protrusions are firmly molded to the tube 3 to form a unitary construction.

Fig. 4 shows a support tube which is provided with conically shaped ends 2 made conical at both ends of the support tube. In this case, preferably, no annular protrusions 13 on the outer surface in the vicinity of the plugs 2 occur, and the plugs 2 preferably have a somewhat greater axial length to prevent the metal pipe from being exposed on the outside when the plugs are pointed made.

Fig. 5 shows a support tube, both ends of which are cut with a flat plane at an angle at the stop 2 to form a pointed end. The pointed end can be made by cutting the support tube at the stop 2 as shown in Fig. 1. In this case, it is also preferable to give the plug 2 a length sufficient to avoid exposing the metal pipe 1 when the support tube is cut at an angle at the stop 2.

Fig. 6 shows an embodiment of a method according to the invention, in which it is ensured that the metal pipes 1 and the resin plugs 2 are alternately arranged and joined together to form a coherent whole, which coherent whole is in turn supplied in a cross-head die. is mounted on an extruder. A number of metal pipes 1 are stacked on an inclined plate 21 with their longitudinal axes in parallel relationship with each other. The stacked pipes are held by movable stops 22. When the stops 22 are lowered by means of rotary combs or discs 23, the stacked pipes are intermittently transferred to the passage 24 one at a time. A comb 25 is in line with the passage 24, and metal pipes 1 in the passage 24 are pushed in the direction of arrow a. By a projection on the comb 25. The metal pipes are thus advanced and inserted between paired rollers 26, which advances the metal pipes further to a crosshead die 27 mounted on the extruder.

Plugs 2 are fed one after the other to passage 24 from a direction transverse to the metal pipes 1. The plugs 2 are initially stacked on top of each other with their centers rotating in parallel with the centers of the metal pipes 1, and the bottom plug 2 is in contact with the metal pipe 1 in the passage 24. A holder 28 is arranged to form part of a passage wall and it holds the stop 2 in the passage 24. When no metal pipe 1 occurs in the holder 28 , the plug 2 falls to the bottom of the container 28 and is set in front of the metal pipe and then guided to the container 28. Since the plug 2 has an outer diameter equal to that of the metal pipe 1, when a vertical wall with a size which only allows one metal pipe to pass through the blocking passage 24 can be provided at the front end of the container 28, only one stop is passed through the wall and it is advanced together with the metal pipe 1 when the metal pipe 1 is pushed in the direction of the arrow a. through the protrusion of the comb 25. At this time, if the plug 2 is formed with a smaller diameter portion, this smaller diameter portion is then fitted into the end of the metal pipe 1 in a sealing manner and the plug 2 is effortlessly connected to the metal pipe 1.

The metal pipe 1 is pushed through the projection of the comb 25 at a traveling speed a which is greater than the speed _b at which the metal pipe is pushed through the pair of clamping rollers 26. When it is advanced through the projection of the comb 25 the metal pipe 1 thus enters the preceding metal pipe and comes into contact with the preceding metal pipe. Thus, if the plug 2 is also formed with a smaller diameter portion at the front end thereof, this portion is fittingly fitted in the rear end of the preceding metal pipe to form a cohesive whole. The coherent assembly is clamped by the paired rollers 26 and gradually advanced to the crosshead die 27.

Since the plug 2 has an outer diameter equal to that of the metal pipe 1, when the plug 2 is bonded alternately with metal pipes 1 to form a cohesive whole, this coherent whole has the same diameter at each section. The coherent whole thus acts as if it were a metal pipe with an even outer diameter. The cohesive whole is therefore suitable for carrying out an extrusion coating thereon. That is, if a resin tube is extruded to coat the cohesive assembly, the resin tube 3 forms a dense coating around the cohesive assembly. Extrusion of the resin tube in this case can be effortlessly carried out by applying to it the usual electrical wire manufacturing operations, wherein metal wires are coated with resin.

The extruded resin-coated cohesive assembly is then cooled by cooling means 29 set in front of the die 27, as shown in Figure 8. Subsequently, the cohesive whole is clamped and removed by take-up rollers 30. The cooling can be carried out by supercharging air, and is most preferably performed by contact with water. After removal, the cohesive whole is cut with a saw at a predetermined place.

In a device as shown in Fig. 8, since the extruder always extrudes a predetermined amount of the resin, the resin tube obtained has a uniform thickness as long as the take-up rollers 30 are rotated at a constant speed and the resin tube is discharged at a constant speed. Thus, according to the present method, a support tube, as shown in Fig. 1, is obtained which has no protrusions on the outer surface thereof. However, if the spinning of the take-up rollers 30 is stopped for a short time, for example, for several seconds, the extruded resin is accumulated to form a locally thick portion. This thick portion forms an annular projection at the exit of the die. When the take-up rollers are then rotated again, the extruded resin is again formed into a casing 3 of the same thickness as before. The height and length of the thick portion can be controlled by the length of time the take-up rollers 30 are stopped and by the amount of resin extruded from the extruder. Thus, a support tube can be obtained which has spaced annular protrusions on its outer surface, as shown in Fig. 2.

A support tube having protrusions of the type shown in Figure 3 can be manufactured by the method described below. As seen in Fig. 9, a crosshead die 27 is mounted on an extruder. The mold 27 is provided with spaced serrations 41 on the wall of the resin passage in the vicinity of the exit. The serrations 41 provide the extruded resin tube with rectilinear protrusions 42 that project outwardly on the surface thereof and extend in the axial direction of the tube. Each of the rollers 43 is spaced a short distance from the die 27 to thereby press each of the rectilinear projections 42. Each roller 43 is provided with a serrated periphery 44. Since the resin tube is still in a softened state as it passes through the rollers 43, each rectilinear protrusion is locally pressed through the serrated periphery 44 of each roller 43 so as to make some small protrusions separated in the axial direction from the tube. Although only one roller 43 is shown in FIG. 9, other corresponding or identical rollers are provided for each rectilinear projection 42. Accordingly, a support tube can be obtained, as shown in Fig. 3, which has a number of small protrusions.

Thus, a coated cohesive whole can be obtained with an even outer surface in each section except for the protrusions, especially viewed in the longitudinal direction of the tube. In other words, the resin tube 3 has neither a band nor a recess at the junction between the metal pipe 1 and the plug 2. After the cohesive assembly has been coated with the resin tube 3, a special consideration is therefore required to determine the locations for the to indicate cutting, because the coherent assembly must be accurately cut at the locations where the plug 2 occurs to produce support tubes which have closed both ends with a plug 2.

The present invention provides a method for accurately cutting the coated cohesive assembly at the locations where the plug 2 occurs, even though it is not possible to identify these locations from the outside with the naked eye after the coating has been carried out. In the present invention, the procedures are applied in which electromagnetic waves are fed to the coated coherent assembly, variations in the electromagnetic waves supplied are determined to find the location where a plug occurs, and the coated coherent assembly is cut at these determined locations. In general, the resin has different electromagnetic properties than the metal. A device for emitting electromagnetic waves is accompanied by a receiving device, which can detect variations in the electromagnetic waves. The coated cohesive assembly is allowed to approach the paired devices and the coated cohesive assembly indicates different sensitivities between the portions where the metal pipe 1 occurs and the portions where the plug 2 occurs, and thus the location where the stop 2 occurs. occurs. According to the invention, the coated cohesive whole is cut at the locations where the plug 2 occurs, based on the principles discussed above.

The devices discussed above for emitting and receiving electromagnetic waves are commercially available. The paired pairs are called a location sensing switch, which is manufactured and marketed by Fuji Denki Seizo Kabushiki Kaisha of Japan under the name "Fuji Kinsetsu Switch". Fig. 7 shows a cutting device provided with such a position sensor. In FIG. 7, reference numeral 31 designates a coated coherent assembly, with 32 a site sensing switch, 33 with a saw, and 34 with a portion where plug 2 occurs, and 35 is a circuit connecting the site sensing switch 32 to a saw 33 . When the portion 34 containing a stop 2 is advanced to the location sensing switch 32, the position sensing switch senses a variation in the electromagnetic waves and thereby emits a signal to the circuit 35 which in turn supplies electric current for rotation and advancement from the saw 33 to the coated cohesive assembly 31 from a direction transverse to the cohesive assembly, and as a result, the cohesive assembly 31 is cut where the plug 2 occurs therein.

Fig. 7 shows an embodiment of the cutting members, wherein the cohesive assembly 31 is cut with the saw 33 located in the vicinity of the position sensor 32. However, the saw 33 can also be set at a location remote from the location sensing switch 32. For example, the saw 33 can be set at a distance from the position sensing switch equal to the support tube length. That is, the saw 33 can be adjusted at the location indicated by a dashed line 36 in Fig. 7. In any case, the plug 2 is cut precisely at the location where the stop occurs, using a position sensor.

A support tube, which has sharp ends at both ends as shown in Figures 4 and 5, is manufactured in the manner discussed below. A support tube having conically pointed ends as shown in FIG. 4 is fabricated by the successive operations in which a support tube is first manufactured with both ends cut along a flat plane perpendicular to the axis of the support tube, as shown in FIG. 1 is shown. The support tube is then cut at both ends to form conically pointed ends, as shown in Fig. 4. In order to cut the support tube ends, as shown in Fig. 10, suitably a roller 50 having a file surface can be placed obliquely against the end of the support tube 3 while the roller 50 is rotated about axis 51 and further the support tube 3 is rotated by turning the center line 51 about the center line 52.

A support tube, the ends of which are cut along an obliquely flat plane, as shown in Fig. 5, can be obtained without difficulty by obliquely cutting a saw against the support tube, the ends of which are initially cut perpendicular to the axis of the support tube as shown in Fig. 1, and then rotating the saw to cut the ends. The support tube shown in Figure 5 can also be obtained by slanting a saw when the coated cohesive unit is cut to a predetermined length.

Fig. 11 illustrates a method that can be used to ensure that there is a resin plug at the end of a metal pipe. Fig. 11 schematically shows the method of fitting the plug appropriately into the metal pipe by four consecutive operations (a) to (d).

In particular, in the first operation (a), a metal pipe 61 is advanced in the direction indicated by the arrow y_, and a subsequent metal pipe 62 accompanying the plug 65 is also moved in the direction to precede to follow pipe 62. In this method, the plug 65 is followed by the plugs 66 and 67, which are stored in a stacked state in a direction transverse to the plug 65 and are separated from the plug 65 by a dividing plate 64. The dividing plate 64 is designed for it to be able to be moved in the horizontal direction indicated by the arrow _x by means of a position sensor 63. The dividing plate 64 is at such a height that two plugs 65 can be placed under the plate, but three plugs 65 cannot be placed under the plate can be placed.

The operation (b) in Fig. 11 shows the state where the subsequent metal pipe 62 is advanced in the direction of y to overtake the preceding metal pipe 61. At this time, the location sensing switch 63 detects the variation in the electromagnetic waves from the metal pipe 61 and the resin plug 65, and the dividing plate 64 moves in the direction indicated by the arrow y. When the plate 64 is moved, the plugs 66 and 67 fall in a stacked relationship until the plug 66 contacts and runs on the subsequent metal pipe 62.

The operation (c) in Fig. 11 shows the state where the subsequent metal pipe 62 is further transferred in the direction y_ together with the preceding metal pipe 61, and the position sensor 63 the electromagnetic wave variation of the resin plug 65 and the metals pipe 62. When the location sensing switch 63 detects the variation, the position sensing switch 63 moves the separator plate 64 in the direction of the arrow x at the operation (c), raising the stop 67 and the subsequent stops, leaving the stop 66 only under the plate 64 .

The operation (d) in Fig. 11 shows the state where the subsequent metal pipe 62 is further advanced in the direction y_ until no metal pipe 62 occurs under the dividing plate 64. In this state, the locating sensor switch 63 still senses the metal pipe 62 and the separator tube 64 still holds the plug 67 and the subsequent plugs located above the plug 67. When the rear end of the metal pipe 62 has passed under the dividing plate 64, the resin stop 66, which runs on the metal pipe 62, falls into the passage through which the subsequent metal pipe 68 can be advanced. As the subsequent metal pipe 68 is advanced further in the y direction, the rear end of the resin plug 66 is fitted into the forward end of the subsequent metal pipe 68, and the operation (a) discussed above is repeated. By repeating the successive operations (a) to (d) in this order, the resin plugs and metal pipes are alternately placed and connected to form a sanitary pendant which is further transferred.

The support tube of the present invention forms a structure that has a resin plug fitted to both ends of a metal pipe to form a core, which is coated with a resin tube to form a unitary article, thereby not extending the metal pipe is exposed. The resin plug is composed of a resin compatible with the resin from which the casing is formed, and the casing is brought into close contact with the plug, thereby keeping the interior of the metal pipe watertight. The support tube thus has the strength of a metal pipe, but will not rust or corrode. The support tube is particularly suitable, as the interior is kept waterproof, so that it will not corrode inside. Furthermore, the support tube, when provided with protrusions on the outer surface thereof, has the additional advantages that creepers, such as ivy and vine, can grip the support tube and swing around the support tube without difficulty, and can also handle a strand or cord the support tube surface should be bonded in a desired location when the stem of the plant is to be attached to the support tube. The support tube can therefore be used in a wide variety of applications. Moreover, the support tube, when made pointed at both ends, becomes very suitable for upright mounting it in the ground by inserting the support tube end into the ground.

The method for manufacturing the support according to the invention is very suitable in that a support tube, which has the advantages discussed above, can be produced continuously without effort and with good efficiency. In particular, the first advantage is that the metal pipes and resin plugs can be reliably placed alternately, and they can be connected continuously to form a cohesive whole, which is then subjected to a continuous extrusion coating, and the process can thus be performed with greater efficiency. The second advantage is that one resin plug is inserted into the gap between the adjacent metal pipes to form the cohesive unit, which is then cut at the center of the resin plug to form a support tube that has plugs at both ends thereof, and this can be easily and effortlessly fitted to stop the metal pipes at each of their ends.

The present invention can be embodied in other specific forms without departing from the scope or essential features. The embodiments disclosed herein are therefore considered to be illustrative in all respects and are not to be construed as limiting, the scope of the invention being indicated by the appended claims rather than the foregoing description, and wherein all changes which are intended and covered by the claims are therefore encompassed thereby.

Claims (10)

1. Support tube, consisting of an inner tube of metal and an outer casing of plastic, and in combination provided with plugs (2) mounted on the ends and stiffeners (13 and 14, respectively) arranged between the plugs. Support tube according to claim 1, characterized in that the stiffeners consist of stiffening rings (13) Support tube according to claim 2, characterized in that the stiffening rings (13) on the casing (3) are formed from the same casing material. Support tube according to claim 1, characterized in that the stiffeners consist of longitudinal ribs (14). Support tube according to claim 4, characterized in that the longitudinal ribs (14) are discontinuous in the longitudinal direction and each consist of a series of crenellated studs separated by recesses. A method of manufacturing a support tube according to any one of the preceding claims, using metal pipes, resin stoppers and resin pipe members, comprising the successive operations of: (a) extracting a single metal pipe from a stock of pipes stacked with their longitudinal axes parallel to each other and to a passage, (b) feeding a resin stopper one by one from a direction transverse to the passage, (c) placing said pipe in said passage and said stopper with its centerlines in a common plane, (d) intermittently transferring said pipes in an axial direction, (e) inserting a stopper into the interstage between the pipes / (f) insertion from each end of said stopper in corresponding ends of said pipes to form a cohesive unit that provides an even diameter, (g) feeding the cohesive assembly into a crosshead die mounted on an extruder, (h) continuously coating the cohesive assembly with a synthetic resin, and (i) cutting the resin-coated cohesive assembly. at a part where the said stop member occurs. A method according to claim 6, characterized in that the advancement of said coherent assembly is stopped intermittently while said extrusion coating is applied thereto to form a circular rib thereon from place to place. Method according to claim 6, characterized in that spaced notches are arranged in the passage wall at the location of the exit in said crosshead die, thereby forming a number of rectilinear protrusions on the outer surface of said coherent whole, and further applying a serrated surface to each of the protrusions to form local recesses on the protrusions while the protrusions are still in a softened state. The method of claim 6, wherein a location sensing switch is mounted on the passageway for said coherent assembly, a sawing member being driven by a sensed variation in the electromagnetic waves between said metal pipe and said resin stoppers determined by said location sensing switch and said coherent assembly is cut by said sawing member at the location where said stopper occurs in said cohesive assembly. 10. A method according to claim 6, characterized in that a location sensing switch is mounted on a passage for said metal pipes and resin stopper members, and said stopper members are fed to said passage one by one by the sensed variation in the said electromagnetic waves between said metal pipe and said resin stopper members determined by said location sensing switch.