Patent Publication Number: US-9890513-B1

Title: Locatable slab assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Taiwanese patent application no. 106116574, filed on May 19, 2017, the entire disclosure of which is hereby incorporated by reference. 
     FIELD 
     The disclosure relates to a locatable slab assembly, more particularly to a locatable slab assembly by which a manhole cover located beneath a pavement can be precisely located. 
     BACKGROUND 
     As shown in  FIG. 1 , a manhole  12  is closed by a manhole cover  11  on the ground surface. Sometimes, the ground surface will be further paved with asphalt. In this case, as the manhole cover  11  may not be flush with the road surface, either road bump or depression would be formed. Traffic accidents may thus occur. 
     To solve this problem, as shown in  FIG. 2 , a manhole opening  12 A is arranged at a depth (about 25 cm to 30 cm) beneath the ground surface, and a pavement  13  is paved on the manhole cover  11 . In this case, to access to the manhole  12 , it is necessary to locate the manhole cover  11 . Taiwanese patent no. 1398567 discloses a method for locating a manhole cover using a metal detector. 
     Taiwanese utility module patent no. M507942 discloses another method for locating a manhole cover. Two radio-frequency identification (RFID) tags are disposed diagonally opposite to each other on the manhole cover. A center of the manhole cover beneath the ground surface may be determined using the two RFID tags. 
     SUMMARY 
     An object of the disclosure is to provide a novel locatable slab assembly, by which a manhole cover located beneath a pavement can be precisely located. 
     According to the disclosure, a locatable slab assembly is used for overlying a manhole cover which is located beneath a lowermost surface of a pavement, and which defines a center line. The locatable slab assembly is liftable by a lifting device which has a gripped head and a connected end segment that is opposite to the gripped head and that has an outer threaded surface. The locatable slab assembly includes a slab body, a tubular member, a protective plug, and an electronic marker. The slab body is configured to fully overlie the manhole cover, and defines a central line in line with the center line. The slab body has an upward surface, a downward surface, a cavity, and a bore. The cavity extends downwardly from the upward surface along the central line to terminate at a cavity bottom. The bore extends downwardly from the cavity bottom along the central line. The tubular member is fitted in the bore, and has an inner threaded region which surrounds the central line, and which defines a lower chamber extending to be in spatial communication with the cavity along the central line. The inner threaded region is configured to be brought into threaded engagement with the outer threaded surface, so as to permit the locatable slab assembly to be lifted by the lifting device. The protective plug has an enlarged head and a plug body which is configured to be inserted into the cavity to permit the enlarged head to be disposed outwardly of the slab body. The plug body is formed with an upper chamber extending to be in spatial communication with the lower chamber along the central line. The electronic marker has an upper segment disposed in the upper chamber and a lower segment disposed in the lower chamber. The electronic marker is configured to permit a region of the pavement in alignment with the center line of the manhole cover to be located. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic cross sectional view illustrating a manhole cover on the ground surface; 
         FIG. 2  is a schematic cross sectional view illustrating a manhole cover located beneath the ground surface; 
         FIG. 3  is an exploded perspective view of a locatable slab assembly according to an embodiment of the disclosure, in which a slab body and binding wires are omitted; 
         FIG. 4  is a top view illustrating steel bars in a slab body of the locatable slab assembly in which a protective plug is omitted; 
         FIG. 5  is a cross-sectional view of the locatable slab assembly; 
         FIG. 6  is a flow chart showing a method for installing the locatable slab assembly; 
         FIG. 7  is a schematic view illustrating a step of reconstructing a manhole opening to be located beneath the ground level; 
         FIG. 8  is a schematic cross-sectional view illustrating the locatable slab assembly disposed to overlie a manhole cover; 
         FIG. 9  is a schematic cross-sectional view illustrating that the locatable slab assembly and the manhole cover are located beneath a pavement; 
         FIG. 10  is a flow chart showing a method for assessing to the manhole cover using the locatable slab assembly; 
         FIG. 11  is a schematic cross-sectional view illustrating a region of the pavement to be located and removed; 
         FIG. 12  is a schematic cross-sectional view illustrating a periphery of the manhole cover to be determined using a template; 
         FIG. 13  is a schematic cross-sectional view illustrating that the pavement and the locatable slab assembly are cut along a cutting line; 
         FIG. 14  is a schematic cross-sectional view illustrating that the pavement and the locatable slab assembly are lifted using a lifting device to form an accessing opening for accessing to the manhole cover; and 
         FIG. 15  is a schematic cross-sectional view illustrating that the cutout portions of the pavement and the locatable slab assembly are refilled in the accessing opening. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 3 to 5 , a locatable slab assembly  2  according to an embodiment of the disclosure is shown to include a slab body  20 , a tubular member  22 , a protective plug  24 , and an electronic marker  25 . The locatable slab assembly  2  is used for overlying a manhole cover  41  (see  FIG. 8 ). The manhole cover  41  is located beneath a lowermost surface of a pavement  44  (see  FIG. 9 ), and defines a center line (C 1 ). The locatable slab assembly  2  is liftable by a lifting device  64  (see  FIG. 14 ). The lifting device  64  has a gripped head  641  and a connected end segment  642  that is opposite to the gripped head  641  and that has an outer threaded surface  643 , for example, with the dimension M32. 
     Referring back to  FIGS. 5 and 8 , it can be observed that the slab body  20  is configured to fully overlie the manhole cover  41  and defines a central line (C 2 ) in line with the center line (C 1 ). The slab body  20  has an upward surface  202 , a downward surface  203 , a cavity  204 , and a bore  206 . The cavity  204  extends downwardly from the upward surface  202  along the central line (C 2 ) to terminate at a cavity bottom  205 . The bore  206  extends downwardly from the cavity bottom  205  along the central line (C 2 ). 
     In this embodiment, referring to  FIGS. 4 and 5 , it can be observed that the slab body  20  is of a steel reinforced concrete structure. The steel reinforced concrete structure of the slab body  20  is configured to simulate the contour of the manhole cover  41 , and may have a predetermined dimension, e.g., 1400 mm×1400 mm×150 mm. In the steel reinforced concrete structure, a plurality of steel bars  201  are arranged into a grid pattern. As shown in  FIG. 4 , for example, eight of the steel bars  201  are arranged in a longitudinal direction, and eight of the steel bars  201  are arranged in a direction transverse to the longitudinal direction. 
     The tubular member  22  is fitted in the bore  206  (see  FIG. 5 ), and has an inner threaded region  223  which surrounds the central line (C 2 ), and which defines a lower chamber  221  extending to be in spatial communication with the cavity  204  along the central line (C 2 ) (see  FIGS. 3 and 5 ). The inner threaded region  223  has a dimension, for example, M32, and is configured to be brought into threaded engagement with the outer threaded surface  643  of the lifting device  64 , so as to permit the locatable slab assembly  2  to be lifted by the lifting device  64  (see  FIG. 14 ). In this embodiment, the tubular member  22  is made of a metal material. 
     The protective plug  24  has an enlarged head  243  and a plug body  244 . The plug body  244  is configured to be inserted into the cavity  204  to permit the enlarged head  243  to be disposed outwardly of the slab body  20 . The plug body  244  is formed with an upper chamber  242  extending to be in spatial communication with the lower chamber  221  along the central line (C 2 ). 
     In this embodiment, the protective plug  24  is made of a plastic material, and is tapered from top to bottom. The protective plug  24  has, for example, a height of 80 mm, a maximum outer diameter of 100 mm, and a minimum outer diameter of 80 mm. The inner chamber  242  has an inner diameter of for example 20 mm, and a height of for example 50 mm. The enlarged head  243  has a height of for example 20 mm. The protective plug  24  has a recess  241  with a dimension, e.g., 50.8 mm×50.8 mm×15 mm. The recess  241  is in spatial communication with the upper chamber  242  along the central line (C 2 ), and is configured to permit a top segment of the tubular member  22  to be received therein when the protective plug  24  is inserted into the cavity  204  (see  FIG. 5 ). 
     The electronic marker  25  has an upper segment  251  and a lower segment  252 . The upper segment  251  has a length of for example 46 mm, and is disposed in the upper chamber  242 . The lower segment  252  has a length of for example 30 mm, and is disposed in the lower chamber  221 . The electronic marker  25  is configured to permit a region  45  of the pavement  44  in alignment with the center line (C 1 ) of the manhole cover  41  to be located (see  FIG. 11 ). Because the lower segment  252  of the electronic marker  25  is disposed in the tubular member  22  made of metal, and because the upper segment  251  of the electronic marker  25  is disposed in the protective plug  24  made of plastic, the signal from the electronic marker  25  can be transmitted upwardly and is less likely to diverge so as to permit the region  45  of the pavement  44  in alignment with the center line (C 1 ) of the manhole cover  41  to be precisely located. 
     The electronic marker  25  may be active or passive markers. In this embodiment, the electronic marker  25  is a radio-frequency identification (RFID) tag, and can generate a specific electromagnetic signal in response to an electromagnetic signal of a specific resonate frequency (for example, 13.56 MHz) from an REID reader. It should be noted that although the electronic marker  25  shown in figures are in the form of cylinder, the electronic marker  25  is actually in a corn-shape and is tapered from bottom to top for facilitating signal transmission. 
     In this embodiment, the locatable slab assembly  2  further includes a post member  220  and a flange member  21 . 
     As shown in  FIG. 5 , the post member  220  extends downward from the tubular member  22  to be embedded in the slab body  20 . The tubular member  22  and the post member  220  are integrally formed into a body with dimension, for example, 50 mm×50 mm×104 mm. The body including the tubular member  22  and the post member  220  is made of a metal material, and has an upper portion disposed upwardly of the flange member  21  by for example 34 mm, and a lower portion disposed downwardly of the flange member  21  by for example 60 mm. The lower chamber  221  may have a depth of for example 60 mm. 
     The flange member  21  extends radially from a juncture between the post member  220  and the tubular member  22  to be embedded in the slab body  20  for reinforcement of the tubular member  22 . The flange member  21  may have a dimension of for example 200 mm×200 mm×10 mm. 
     In this embodiment, as shown in  FIGS. 3 and 4 , the flange member  21  has four through holes  212  at its corners, and is secured to innermost bars segments  207  of the steel bars  201  relative to the central line (C 2 ) using four binding wires  26 . Each of the through holes  212  may have a dimension of for example 12 mm. Two adjacent parallel ones of the steel bars, other than the innermost ones of the steel bars  201 , are spaced apart from each other by a gap of for example 150 mm. 
     In this embodiment, as shown in  FIG. 3 , the locatable slab assembly  2  further includes a tubular bolt  23  which has a bolt head  233 , an inner surface  234 , and an outer bolt threaded surface  231 , and which is detachably secured to the tubular member  22 . The tubular bolt  23  may have a height of for example 40 mm. The bolt head  233  may have an outer diameter of for example 46 mm. 
     The inner surface  234  defines an inner space  230  which is configured to accommodate the lower segment  252  of the electronic marker  25  when the tubular bolt  23  is secured to the tubular member  22 , and which may have a depth of for example 30 mm and an inner diameter of for example 20 mm. 
     The outer bolt threaded surface  231  is configured to be in threaded engagement with the inner threaded region  223  so as to permit the tubular bolt  23  to serve as a spacer between the tubular member  22  and the electronic marker  25 . The outer bolt threaded surface  231  may have a dimension, for example, M32. 
     In this embodiment, the tubular bolt  23  is made of a metal material. Because the lower segment  252  of the electronic marker  25  is disposed in the tubular bolt  23  made of metal, the signal from the electronic marker  25  is less likely to diverge. 
     As shown in  FIG. 6 , a method for installing the locatable slab assembly  2  includes steps  31  to  33 . 
     In step  31 , as shown in  FIGS. 6 and 7 , an upper segment  40 A of the manhole  40 , which is near the ground level, is widened so as to permit the manhole cover  41  to be located at a depth of for example 25 cm beneath the ground level. The widened upper segment  40 A of the manhole  40  extends from the ground level to terminate at a base surface  40 B with a manhole opening  410 . The manhole cover  41  is disposed to cover the manhole opening  410 . The base surface  40 B may have an inner dimension of for example 1600 mm×1600 mm. 
     In step  32 , as shown in  FIGS. 6 and 8 , the base surface  40 B surrounding the manhole cover  41  is solidified. A soft foam layer  42 , which may have a thickness of for example 2 mm, has a surface area substantially the same as that of the manhole cover  41 , and is disposed to fully overlie the manhole cover  41  to serve as a spacer between the manhole cover  41  and the locatable slab assembly  2 . Then, the locatable slab assembly  2  is disposed on the soft foam layer  42  such that the central line (C 2 ) of the locatable slab assembly  2  is in line with the center line (C 1 ) of the manhole cover  41 . The provision of the soft foam layer  42  can prevent the manhole cover  41  from being damaged by the locatable slab assembly  2 . 
     In step  33 , as shown in  FIGS. 6 and 9 , a spacer slice  43  with an opening  431  is sleeved on the enlarged head  243  of the protective plug  24  to cover on the upward surface  202  of the slab body  20 . The spacer slice  43  is made of a flexible material such as an acrylic elastic material, and has a surface area substantially the same as that of the flange member  21  so as to be disposed in alignment with the flange member  21  along the central line (C 2 ). The opening  431  has a diameter of for example 97 mm. Because the spacer slice  43  is flexible and has the opening  431  slightly smaller than the maximum diameter of the protective plug  24 , the spacer slice  43  can be stretched to be fittingly sleeved on the protective plug  24 . Thereafter, the upward surface  202  of the slab body  20  uncovered by the spacer slice  43  is coated with asphalt oil, and then the base surface  40 B and the locatable slab assembly  2  are paved with asphalt to form the pavement  44  such that an uppermost surface of the pavement  44  is flush with the ground level. A distance between the uppermost surface of the pavement  44  and the upward surface  202  of the slab body  20  is for example 100 mm. 
     As shown in  FIG. 10 , a method for assessing to the manhole cover  41  using the locatable slab assembly  2  includes steps  51  to  56 . 
     In step  51 , an REID reader (not shown) is used for locating the electronic marker  25  so as to locate the central line (C 2 ) of the locatable slab assembly  2  (see  FIG. 9 ) to thereby determine the region  45  of the pavement  44  which may have a diameter of for example 150 mm and a height of for example 100 mm (see  FIG. 11 ). 
     In step  52 , as shown in  FIG. 11 , the region  45  is cored out from the pavement  44  using a conventional tool such as a pavement core drilling machine (not shown). Because the bonding force between the protective plug  24  and the asphalt (the pavement  44 ) is stronger than that between the protective plug  24  and the concrete (the slab body  20 ), the protective plug  24  will be removed from the cavity  204  of the slab body  20  when the region  45  is cored out from the pavement  44 . Thereafter, the electronic marker  25  is also removed. 
     In step  53 , as shown in  FIG. 12 , a jig  61  is fitted into the cavity  204  of the slab body  20  to permit a through hole  60  of the jig  61  to extend along the central axis (C 2 ). Next, a lower segment of an index post  62  is inserted into the through hole  60  to permit an upper segment of the index post  62  to extend along the central axis (C 2 ) out of the uppermost surface of the pavement  44 . Then, a template  63  with a through bore  630  is fittingly sleeved on the upper segment of the index post  62  to overlie on the uppermost surface of the pavement  44 . The template  63  may have a plurality of cutouts (not shown) for labeling the pavement  44  corresponding to the periphery of the locatable slab assembly  2 . The pavement  44  can be labeled by applying paint to the pavement  44  through the cutouts of the template  63  to form a mark. The labeled area may have a dimension of for example 1200 mm×1200 mm or 1300 mm×1300 mm. 
     In step  54 , the template  63 , the index post  62 , the jig  61 , and the tubular bolt  23  are removed, and the pavement  44  and the locatable slab assembly  2  above the manhole cover  41  are cut along the mark. As shown in  FIG. 13 , a cutting line  441  extends from the pavement  44  through the locatable slab assembly  2  to terminate at the base surface  40 B. 
     In step  55 , as shown in  FIG. 14 , the outer threaded surface  643  of the lifting device  64  is brought into threaded engagement with the inner threaded region  223  of the tubular member  22  so as to be secured to the locatable slab assembly  2 . Then, the gripped head  641  is gripped by a hoist (not shown), the cutout portions of the pavement  44  and the locatable slab assembly  2  are lifted by the hoist through the lifting device  64  to form an accessing opening  40 C. After the soft foam layer  42  and the manhole cover  41  are removed, an operator can access to the manhole  40 . 
     After the operator has finished his work, the manhole cover  41  is disposed to cover the manhole opening  410 , the soft foam layer  42  is disposed to overlie the manhole cover  41 , the cutout portions of the pavement  44  and the locatable slab assembly  2  can be refilled in the accessing opening  40 C, and the tubular bolt  23 , the electronic marker  25 , the region  45  of the pavement  44  together with the protective plug  24  can be moved to their original positions, as shown in  FIG. 15 . Gaps (G) formed on the pavement  44  can be filled with an adhesive (MS-R301, Retek International Equipment Co., Ltd., Taiwan). Because the gaps (G) can be observed from the ground level, it is more convenient to access to the manhole  40  the next time. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. 
     While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.