Waterproof plug for empty pipe

Abstract

To provide a waterproof plug that obtains sufficient waterproof function even when it is used in an empty pipeline with a large aperture.SOLUTION: An waterproof plug 11 for an empty pipeline comprises a sealing member 13 made of an elastic material, and pinching means 15 of compressing the sealing member 13 in a front-rear direction to expand the diameter of an outer peripheral sealing surface 31 so as to be brought into close contact with the inner peripheral surface of a pipeline 23. The sealing surface 31 is formed with a cylindrical circumferential surface part 31a facing the inner peripheral surface of the pipeline 23 and extending in the front-rear direction, and a conical deformed peripheral surface part 31b inclined with respect to the peripheral surface part 31a at a rear adjacent position of the peripheral surface part 31a. Consequently, in the middle of the sealing surface 31 in the front-rear direction, a ridgeline part 37 having an obtuse angle of a corner part in a cross-sectional shape, and the ridgeline part 37 whose diameter is to be expanded is strongly brought into contact with the inner peripheral surface to improve adhesion, thereby obtaining high holding force.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a waterproof plug for preventing water or foreign matter from entering an empty pipe, such as a spare pipe provided for future reinforcement of a power cable or a communication cable or for responding to an accident. [Background technology]

[0002] Waterproof plugs with structures such as those described in Patent Documents 1 and 2 below are still in use today.

[0003] These waterproof plugs are configured so that a sealing member made of an elastic material such as rubber is sandwiched between two front and rear members and compressed, causing the sealing member to expand and deform so as to fit closely to the inner circumferential surface of the pipeline. The two front and rear members and the sealing member are held in place by being pierced by an axial member extending in the front-to-rear direction, and the sealing member is compressed by tightening a nut. The sealing member (rubber plug body) in Patent Document 1 is cylindrical, while the sealing material (double annular rubber packing) in Patent Document 2 is shaped as two overlapping donut-shaped rubber rings with holes.

[0004] The waterproof plug constructed as above is attached to the end of an underground buried pipe. The expanded and deformed sealing member fits closely to the inner periphery of the pipe, preventing water leakage and the intrusion of soil and sand from the buried pipe. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Jpn. Jpn. Published No. 63-11861 [Patent Document 2] Jpn. Jpn. Published No. 61-25310 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when water or the like gets in, pressure is applied to the front member. If the diameter of the pipe is small, it is difficult for pressure to be applied that exceeds the adhesion force of the sealing member to the pipe, but the larger the diameter of the pipe, the higher the pressure that is applied, and there is a risk that the waterproof plug will come off the pipe end opening.

[0007] As mentioned above, waterproof plugs are used in vacant conduits to facilitate future cable reinforcement and accident response, and are an important technology for removing utility poles, for example. For this reason, it is necessary to ensure that waterproofing is achieved even in large-diameter vacant conduits.

[0008] The main object of the present invention is to provide a waterproofing function that is sufficient even when used in an empty pipeline having a large diameter. [Means for solving the problem]

[0009] The means for achieving this is a waterproof plug for an empty pipeline equipped with a sealing member made of an elastic material and a clamping means for compressing the sealing member in the front-to-back direction to expand and deform the outer sealing surface to fit closely against the inner peripheral surface of the pipeline, wherein the sealing surface is formed with a cylindrical circumferential surface portion which faces the inner peripheral surface of the pipeline and which extends in the front-to-back direction, and a deformed circumferential surface portion which is inclined relative to the circumferential surface portion at a position adjacent to the rear of the circumferential surface portion, and a ridge portion is formed midway between the front-to-back direction on the sealing surface, the corners of which in the cross-sectional shape have an obtuse angle.

[0010] In this configuration, when the sealing member is compressed in the front-rear direction by the clamping means in the pipeline, the outer sealing surface comes into close contact with the inner peripheral surface of the pipeline. At this time, the circumferential surface portion located at the front of the sealing surface deforms so as to protrude outward toward the outer periphery as it moves toward the rear, forcing the ridge portion into closer contact with the inner peripheral surface of the pipeline. Unlike the deformation mode of the circumferential surface portion, the deformed circumferential surface portion deforms so as to protrude outward in a manner that is recessed from the inner peripheral surface of the pipeline, forcing the ridge portion into close contact with the inner peripheral surface of the pipeline so as to stand upright. Effect of the Invention

[0011] As described above, according to the present invention, the sealing surface of the sealing member is configured such that the ridges are locally deformed to expand in diameter, resulting in high adhesion. Moreover, the angle of the ridges is obtuse, and there are no unnecessary deformed parts that may cause twisting or cutting, resulting in highly uniform adhesion all around. Therefore, sufficient waterproofing can be achieved even when used in a large-diameter empty pipe. [Brief description of the drawings]

[0012] [Figure 1] FIG. 3 is a cross-sectional view of an empty pipeline waterproof plug in use. [Diagram 2] One-sided cross-sectional view of a waterproof plug for an empty pipeline. [Diagram 3] FIG. [Figure 4] FIG. 4 is a cross-sectional view of a mold for forming the seal member. [Diagram 5] FIG. 4 is an enlarged half-sectional view showing the waterproof plug for an empty pipe in use. [Figure 6] FIG. 4 is an explanatory diagram showing a state in which the seal member is compressed and deformed. [Figure 7] FIG. 4 is a cross-sectional view of a seal member used in the test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment of the present invention will be described below with reference to the drawings.

[0014] A cross-sectional view of an empty pipe waterproof plug 11 (hereinafter referred to as a "waterproof plug") in use is shown in Fig. 1. The waterproof plug 11 is used by attaching it to the pipe end of an empty pipe among a plurality of cable protection pipes 22 connected to hand holes 21 buried underground, and has the function of preventing water, etc. from entering the hand holes 21 through the pipe 23.

[0015] The structure of the waterproof plug 11 is as shown in Figure 2. That is, the waterproof plug 11 has a seal member 13 made of an elastic material, and a clamping means 15 that compresses the seal member 13 in the front-rear direction to expand the diameter of the outer circumferential seal surface 31.

[0016] The sealing member 13 is formed in an approximately short cylindrical shape to match the circular cross-sectional shape of the pipeline 23. The diameter of the largest diameter part of the sealing member 13 in the normal state, i.e., before compression, is slightly smaller than the inner diameter of the pipeline 23, and is of a size that provides a gap between the inner peripheral surface of the pipeline 23 for insertion.

[0017] The front and rear ends of the seal member 13 are formed with parallel clamped surfaces 32, 33, and the surface surrounding the outer periphery between these clamped surfaces 32, 33 is the above-mentioned seal surface 31. The clamped surfaces 32, 33 are flat surfaces with which the clamping means 15 comes into contact.

[0018] The clamped surface 32 at the front end is disk-shaped, and the clamped surface 33 at the rear end is annular as shown in Fig. 3. In other words, the seal member 13 has a circular plate-shaped front plate portion 34 formed at the front end, and a peripheral wall portion 35 formed around the entire periphery of the rear surface of the front plate portion 34, with a hollow portion 36 formed inside the peripheral wall portion 35. The inner circumferential surface 35a of the peripheral wall portion 35 has a draft angle for releasing the seal member 13 from the mold during molding. The hollow portion 36 is a portion that contributes to reducing the weight of the seal member 13 and improving its deformability.

[0019] A through hole 34a is formed in the center of the front plate portion 34. A rounded corner 34b is formed at the tip corner of the front plate portion 34.

[0020] The clamped surface 33 at the rear end, that is, the upper end surface 35b of the peripheral wall portion 35, is set to a size sufficient to receive the clamping force of the clamping means 15. The clamped surface 33 at the rear end may have a width W of, for example, about 10 mm or more.

[0021] The sealing surface 31 is a portion that is expanded in diameter and deformed by the clamping pressure applied by the clamping means 15 and comes into close contact with the inner peripheral surface of the pipe 23 .

[0022] This seal surface 31 is formed with a cylindrical circumferential surface portion 31a that faces the inner circumferential surface of the pipeline 23 and spreads in the front-to-rear direction, and a deformed circumferential surface portion 31b that is inclined relative to the circumferential surface portion 31a at a position adjacent to the rear of the circumferential surface portion 31a. By forming the circumferential surface portion 31a and the deformed circumferential surface portion 31b, the seal surface 31 has one ridge portion 37 in the middle in the front-to-rear direction. The angle α (see FIG. 2) of the corner of the cross-sectional shape of the ridge portion 37 is an obtuse angle.

[0023] The contour line of the circumferential surface portion 31a extends in the front-rear direction, and is continuous with the deformed circumferential surface portion 31b via an obtuse-angled ridge portion 37. The ridge portion 37 is an obtuse angle, i.e., greater than a right angle and smaller than two right angles, so the diameter of the deformed circumferential surface portion 31b is smaller than that of the circumferential surface portion 31a. The contour line of the deformed circumferential surface portion 31b may be a straight line like the contour line of the circumferential surface portion 31a, or may be a curved line, but this example shows an example in which it is a straight line. Specifically, the deformed circumferential surface portion 31b is conical.

[0024] The position of the ridgeline portion 37 in the fore-aft direction of the seal surface 31 should be set within a range of about one-third of the fore-aft direction length of the seal surface 31, centered on the midpoint of the fore-aft direction of the seal surface 31. If the ridgeline portion 37 is too far forward, sufficient radial expansion deformation cannot occur, and if it is too far rearward, the ridgeline portion 37 cannot stand upright against the inner circumferential surface of the pipeline 23.

[0025] If the angle α (see FIG. 2) of the corner of the ridgeline portion 37 is too small, the ridgeline portion 37 becomes thin and weak, so it is desirably about 135° or more, for example, in the range of about 140° to 160°. In terms of the relationship between the angle α and the inclination angle of the inner circumferential surface 35a of the peripheral wall portion 35, the angle α is set to be larger than the inclination angle of the inner circumferential surface 35a.

[0026] The material of the seal member 13 is made of a suitable rubber, such as EPDM (ethylene propylene diene rubber).

[0027] In the seal member 13 having the above-mentioned shape, a parting line 38 (see the imaginary line in FIG. 2) is set at the front end. That is, the parting line 38 is set at the base of the rounded corner portion 34b of the entire periphery of the tip of the front plate portion 34. FIG. 4 shows molds 41, 42 for manufacturing the seal member 13, and as shown in this figure, the molds 41, 42 are structured so that a parting line 43 on the outer circumferential surface is formed at the base of the portion corresponding to the rounded corner portion 34b.

[0028] The clamping means 15 for compressing and deforming such a sealing member 13 is composed of a pressing plate 51 that presses the front end face of the sealing member 13, a receiving plate 52 that receives the rear end face of the sealing member 13, and an axial member 53 and a tightening nut 54 that connect and integrate these together with the sealing member 13.

[0029] The pressure plate 51 and the receiving plate 52 are made of metal disks, and both are made of flat plate material. The pressure plate 51 is the same size as the front end face of the seal member 13, and has a through hole 51a formed in its center. The receiving plate 52 is formed larger than the inner diameter of the pipe 23, i.e., larger than the pressure plate 51, and is large enough to hook onto the edge of the pipe end opening. A through hole 52a is also formed in the center of the receiving plate 52, similar to the pressure plate 51. These through holes 51a, 52a are the same as the through hole 34a of the seal member 13, and are holes through which the shaft member 53 is inserted.

[0030] The shaft member 53 is constituted by an eyebolt, and its tip is inserted through the pressing plate 51, the seal member 13 and the receiving plate 52 in that order, and a tightening nut 54 is held at the tip protruding from the receiving plate 52.

[0031] The annular portion 53a at the head of the shaft member 53 is a portion to which an end of a wire (not shown) such as a call line is attached.

[0032] The waterproof plug 11 constructed as above has the pressing plate 51 and sealing member 13 inserted into the pipe end opening of the empty pipe, and the receiving plate 52 pressed against the edge of the pipe end opening to block the pipe 23, and this state is maintained by the clamping means 15. That is, as shown in Figure 5, by tightening the clamping means 15, the pressing plate 51 is attracted and the sealing member 13 is compressed and deformed in the front-to-rear direction, and the sealing surface 31 of the sealing member 13 is expanded in diameter and brought into close contact with the inner peripheral surface of the pipe 23.

[0033] 6 shows the action of clamping means 15 during tightening. When clamping nut 54 of clamping means 15 is rotated to tighten, an internal force is generated in seal member 13 due to the external force received from pressing plate 51 and receiving plate 52 on front and rear clamped surfaces 32, 33 of seal member 13, causing seal surface 31 and inner circumferential surface 35a to bulge. At this time, ridge line portion 37 of seal surface 31 undergoes the greatest radial expansion while retreating, and comes into localized close contact with the inner circumferential surface of pipe 23.

[0034] That is, the circumferential surface portion 31a located at the front side (the back side of the pipe 23) of the sealing surface 31 protrudes outward toward the outer periphery as the ridge line portion 37 located at the rear side approaches. At this time, the deformed circumferential surface portion 31b, which is deformed to bulge due to the internal force, acts to push the obtuse-angled ridge line portion 37 forward or to erect the ridge line portion 37. That is, compared to the circumferential surface portion 31a, which has a shape extending in the front-rear direction, the deformed circumferential surface portion 31b has a shape that converges toward the rear, and the angle between the rear part of the ridge line portion 37, which has been deformed to expand in diameter, and the inner circumferential surface of the pipe 23 is larger than the angle between the front part of the ridge line portion 37 and the inner circumferential surface of the pipe 23. In this way, the deformed circumferential surface portion 31b is in a state of being braced in a manner that makes it restrain against the inner circumferential surface of the pipe 23, and directs the ridge line portion 37 toward the front. In particular, since the deformed peripheral surface portion 31b is conical and has a larger inclination angle than the inner peripheral surface 35a of the peripheral wall portion 35 that forms the cavity 36, the ridge line portion 37 can be made to stand up more strongly during compression. As a result, the ridge line portion 37 is pressed more strongly against the inner peripheral surface of the pipe 23.

[0035] In this manner, the seal surface 31 of the seal member 13 is configured such that the ridges 37 are in localized contact, thereby achieving a high degree of contact.

[0036] In addition, the angle of the ridgeline 37 is obtuse, so it has a solid shape, and the parting line 38 is set at the front end, so no burrs are generated on the ridgeline 37. Therefore, the ridgeline 37 does not twist or break, and a uniformly high adhesion is obtained all around.

[0037] Such high adhesion due to the deformation of the seal surface 31 can be stably obtained. That is, the seal member 13 has a shape having clamped surfaces 32, 33 at the front end and the rear end, a circular plate-shaped front plate portion 34 at the front end, a peripheral wall portion 35 formed on the entire circumference of the rear surface of the front plate portion 34, and a hollow portion 36 inside the peripheral wall portion 35. Therefore, the front end surface of the seal member 13 clamped by the pressing plate 51 is highly integrated with the pressing plate 51, coupled with the fact that it is connected by the shaft member 53 inserted into the through holes 51a, 34a, and the compressive force can be applied equally to the entire surface. Moreover, even with the configuration having the hollow portion 36 inside, the deformed peripheral surface portion 31b is conical, so rigidity in the front-rear direction is obtained, and although the clamped surface 33 at the rear end strongly contacts the receiving plate 52, it is difficult for the receiving plate 52 to be displaced from the receiving plate 52. As a result, the compressive deformation of the seal member 13 caused by the clamping means 15 is stable and uniform according to the degree of clamping, thereby obtaining the desired adhesion.

[0038] A test was conducted to confirm the watertightness of the waterproof plug 11 having the above-mentioned configuration. In the test, the waterproof plug was attached to a pipeline, and a predetermined water pressure was applied and maintained for a certain period of time, and the presence or absence of water leakage was visually checked.

[0039] First, the embodiment product having a ridge line portion was compared with a comparative product having a conventional straight shape without a ridge line portion.

[0040] The test product was used in a pipeline with a diameter of 125 mm, and the waterproof plugs of both the example product and the comparative example product had the same configuration as described above. As shown in Fig. 7(a), the sealing member 13 of the example product has a diameter of 110 mm at the clamped surface 32 at the front end. The outer diameter of the clamped surface 33 at the rear end is 90 mm, and the inner diameter is 70 mm. The height (length in the front-to-rear direction) of the sealing member 13 is 50 mm, and the height of the circumferential surface portion 31a is 20 mm. The depth of the hollow portion 36 is 42 mm, and the diameter of the through hole 34a is 11 mm.

[0041] The comparative waterproof plug had a sealing member with a diameter of 110 mm and a height of 50 mm.

[0042] When a water pressure of 0.05 MPa was applied and maintained for 30 minutes, water leakage occurred in the comparative example product, but no water leakage was observed in the example product.

[0043] This test shows that the example products having ridges have high water-stopping properties.

[0044] Next, it was investigated whether or not watertightness could be achieved with a different diameter from that described above.

[0045] The test pieces used were one for use in a 100 mm diameter pipeline and one for use in a 150 mm diameter pipeline. The water pressure in this test was 0.1 MPa.

[0046] As shown in Fig. 7(b), the test seal member 13 for a 100 mm diameter has a diameter of 91 mm at the front end of the clamped surface 32. The outer diameter of the rear end of the clamped surface 33 is 70 mm, and the inner diameter is 51 mm. The height (length in the front-rear direction) of the seal member 13 is 40 mm, and the height of the circumferential surface portion 31a is 15 mm. The depth of the cavity portion 36 is 35 mm, and the diameter of the through hole 34a is 11 mm.

[0047] As shown in Fig. 7(c), the diameter of the clamped surface 32 at the front end of the seal member 13 for a 150 mm diameter is 137 mm. The outer diameter of the clamped surface 33 at the rear end is 117 mm, and the inner diameter is 87 mm. The height (length in the front-rear direction) of the seal member 13 is 50 mm, and the height of the circumferential surface portion 31a is 20 mm. The depth of the cavity portion 36 is 42 mm, and the diameter of the through hole 34a is 11 mm.

[0048] In addition, because the water pressure and retention time were different from those in the previous test, tests were also conducted on the example product with a diameter of 125 mm. The example product with a diameter of 125 mm was the same as that described above.

[0049] As a result of the tests, no leakage was observed in any of the test products.

[0050] This shows that watertightness can be achieved even in large-diameter pipes.

[0051] As described above, the waterproof plug 11 can firmly adhere the sealing surface 31 of the sealing member 13 to the inner peripheral surface of the pipeline 23, so that sufficient waterproofing can be achieved even when used in a large-diameter empty pipeline, such as 125 mm or 150 mm, to which a large pressure may be applied.

[0052] Furthermore, since the pressing plate 51 and the receiving plate 52 of the clamping means 15 are formed from flat plate material, they can be easily manufactured at low cost.

[0053] The above configuration is one embodiment for carrying out the present invention, and the present invention is not limited to only the above configuration, and other configurations can also be adopted.

[0054] For example, the sealing surface 31 may have a plurality of ridges 37 . [Explanation of symbols]

[0055] 11…Waterproof plug for empty pipe line 13...Sealing material 15...Press means 23…Pipe line 31…Seal surface 31a...Circumferential surface part 31b...Deformed peripheral surface part 32,33…Sandwiched surface 34…Front plate part 35...peripheral wall part 36...Cavity part 37…Ridge 38…Parting line 51…Press plate 52…Receiving plate

Claims

1. A waterproof plug for an empty pipe, comprising a sealing member made of an elastic material and a clamping means for compressing the sealing member in the front-rear direction to expand and deform the outer sealing surface of the sealing member to fit closely to the inner circumferential surface of the pipe, The sealing surface is formed with a cylindrical circumferential surface portion facing the inner circumferential surface of the pipeline and extending in the front-rear direction, and a deformed circumferential surface portion adjacent to the rear of the circumferential surface portion and inclined relative to the circumferential surface portion, A ridge portion having an obtuse angle at a corner in a cross-sectional shape is formed at a midpoint in the front-rear direction of the sealing surface, The sealing member has flat clamped surfaces at its front and rear ends that are clamped by the clamping means, a front plate portion formed at a front end thereof in the shape of a circular plate, and a peripheral wall portion formed around the entire periphery of a rear surface of the front plate portion; A hollow portion is provided inside the peripheral wall portion. Waterproof plug for empty pipes.

2. The deformed peripheral surface is conical. The waterproof plug for an empty pipeline according to claim 1.

3. The parting line was set at the front end. The waterproof plug for an empty pipeline according to claim 1 or 2.

4. the clamping means includes a pressing plate for pressing a front end surface of the seal member and a receiving plate for receiving a rear end surface of the seal member, The pressing plate and the receiving plate are formed of flat plate material. The waterproof plug for an empty pipe according to any one of claims 1 to 3.

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