Abstract:
A rechargeable battery includes: an electrode assembly configured to perform charging and discharging; a case enclosing the electrode assembly; a cap plate coupled to an opening of the case; an electrode terminal engaging a terminal hole of the cap plate; and an insulator between the cap plate and the electrode terminal, wherein the insulator comprises: a fluid receiving recess at a side of the electrode terminal to receive fluid, and an outlet extending through the insulator from the fluid receiving recess to discharge the received fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2012-0131865 filed in the Korean Intellectual Property Office on Nov. 20, 2012, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The described technology relates generally to a rechargeable battery. 
         [0004]    2. Description of the Related Art 
         [0005]    A rechargeable battery is a battery configured to be repeatedly charged and discharged, which is different from a primary battery. Small capacity rechargeable batteries are often used in portable and small electronic devices, such as mobile phones, notebook computers, and camcorders. Large capacity rechargeable batteries may be used as a power source for driving a motor of a hybrid car or an electric car. 
         [0006]    Electrolyte fluids of rechargeable batteries, however, may permeate into internal spaces that are intended to be isolated from the electrolyte fluid, due to limitations in the performance and design of internal sealing materials. As a result, an electrode terminal may be corroded. 
         [0007]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY 
       [0008]    The described technology has been made in an effort to provide a rechargeable battery which prevents or reduces electrolyte fluid from permeating into a space between the electrode terminal and a cap plate from the outside. 
         [0009]    An exemplary embodiment provides a rechargeable battery, including: an electrode assembly configured to perform charging and discharging; a case enclosing the electrode assembly; a cap plate coupled to an opening of the case; an electrode terminal engaging a terminal hole of the cap plate; and an insulator between the cap plate and the electrode terminal, wherein the insulator comprises: a fluid receiving recess at a side of the electrode terminal to receive fluid, and an outlet extending through the insulator from the fluid receiving recess to discharge the received fluid. 
         [0010]    The fluid receiving recess may be formed adjacent to a periphery of the electrode terminal, and the outlet may include first and second outlets at opposing ends of the cap plate in a longitudinal direction of the cap plate. 
         [0011]    The electrode terminal may include: a rivet terminal in the terminal hole; and a plate terminal coupled to the rivet terminal and at an external surface of the cap plate, and the insulator may be between the plate terminal and the cap plate, and surround a periphery of the plate terminal. 
         [0012]    The fluid receiving recess may be around a periphery of the plate terminal. 
         [0013]    The plate terminal may include a first receiving recess in a surface facing the insulator, and the insulator may include a first wall in the first receiving recess. 
         [0014]    The cap plate may include a second receiving recess in a surface facing the insulator, and the insulator may include a second wall in the second receiving recess. 
         [0015]    The electrode terminal may include a cathode terminal and an anode terminal, the anode terminal may be electrically coupled to the cap plate, and the cathode terminal and the cap plate may further include an external short part therebetween. 
         [0016]    The external short part may include: a short protrusion extending from the plate terminal and facing a short hole at the cap plate; and a short member installed at the short hole while facing the short protrusion. 
         [0017]    The first receiving recess may include: a first receiving recess adjacent to an outer side of a rivet terminal of the cathode terminal; and a second receiving recess adjacent to the short protrusion. 
         [0018]    The first wall may include: a first wall coupled to the first receiving recess; and a second wall coupled to the second receiving recess. 
         [0019]    The second receiving recess and the second wall may be adjacent to the rivet terminal of the cathode terminal. 
         [0020]    The electrode terminal may include a cathode terminal and an anode terminal, and the insulator may include: a first insulator between the cathode terminal and the cap plate and surrounding a periphery of a plate terminal of the cathode terminal; and a second insulator between the anode terminal and the cap plate and surrounding a periphery of a plate terminal of the anode terminal. 
         [0021]    The fluid receiving recess may include: a first fluid receiving recess around a periphery of the plate terminal of the cathode terminal; and a second fluid receiving recess around a periphery of the plate terminal of the anode terminal. 
         [0022]    The first receiving recess may include: a first receiving recess at the plate terminal of the cathode terminal facing the first insulator; and a second receiving recess at the plate terminal of the anode terminal facing the second insulator. 
         [0023]    The first wall may include: a first wall of the first insulator in the first receiving recess; and a second wall of the second insulator in the second receiving recess. 
         [0024]    The second receiving recess may include: a third receiving recess in a surface of the cap plate facing the first insulator; and a fourth receiving recess in a surface of the cap plate facing the second insulator. 
         [0025]    The second wall may include: a third wall of the first insulator in the third receiving recess; and a fourth wall formed of the second insulator in the fourth receiving recess. 
         [0026]    According to the exemplary embodiment, the fluid receiving recess and the outlet are included in the insulator installed between the electrode terminal and the cap plate, so that the electrolyte fluid entering from the outside is induced in the fluid receiving recess and is discharged through the outlet, thereby achieving an effect of preventing or reducing the electrolyte fluid from permeating therein. Accordingly, it is possible to prevent or reduce the electrode terminal installed at the terminal hole of the cap plate from being corroded. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a schematic perspective view of a rechargeable battery according to a first exemplary embodiment of the present invention. 
           [0028]      FIG. 2  is a schematic cross-sectional view taken along line II-II of  FIG. 1 . 
           [0029]      FIG. 3  is a schematic exploded perspective view of a cathode terminal side. 
           [0030]      FIG. 4  is a schematic cross-sectional view of a rechargeable battery according to a second exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    Hereinafter, the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Throughout the specification, like reference numerals designate like elements throughout the specification. 
         [0032]    A rechargeable battery includes an electrode assembly including electrodes at both surfaces of a separator, a case for accommodating the electrode assembly, and a cap plate coupled to an opening of the case, and an electrode terminal installed in the cap plate to be connected to the electrode through a lead tab. 
         [0033]    For example, the electrode terminal includes a rivet terminal positioned in an inner side of the cap plate and a terminal hole to be electrically connected to the lead tab, and a plate terminal included outside the cap plate to be connected to the rivet terminal. 
         [0034]    A gasket is interposed between the rivet terminal and the terminal hole, and an insulator is interposed between the plate terminal and the cap plate, to seal a space between the electrode terminal and the terminal hole and electrically insulate the electrode terminal and the cap plate. 
         [0035]      FIG. 1  is a schematic perspective view of a rechargeable battery  100  according to a first exemplary embodiment of the present invention, and  FIG. 2  is a schematic cross-sectional view taken along line II-II of  FIG. 1 . 
         [0036]    Referring to  FIGS. 1 and 2 , the rechargeable battery  100  of the first exemplary embodiment includes an electrode assembly  30  for charging and discharging current, a case  35  surrounding (e.g., enclosing or accommodating) the electrode assembly  30 , a cap plate  40  coupled to an opening of the case  35 , a first electrode terminal  51  (hereinafter, referred to as a “cathode terminal”) and a second electrode terminal  52  (hereinafter, referred to as an “anode terminal”) installed in the cap plate  40 , an external short part  60  included at a side of the cathode terminal  51 , and an insulator  70  installed between the cathode terminal  51  and the cap plate  40 . 
         [0037]    For example, the electrode assembly  30  may be formed by positioning a first electrode  31  (hereinafter, referred to as a “cathode”) and a second electrode  32  (hereinafter, referred to as an “anode”) at opposing surfaces of the separator  33 . The separator  33  is an insulating material. The cathode  31 , the separator  33 , and the anode  32  are wound or rolled together to form the electrode assembly  30 . 
         [0038]    The cathode  31  and the anode  32  include coated portions  31   a  and  32   a  formed by coating or depositing an active material on a current collector of a metal plate, and uncoated or exposed portions  31   b  and  32   b  formed as a current collector on which the active material is not coated or deposited, respectively. 
         [0039]    The uncoated portion  31   b  of the cathode  31  is formed at one end of the cathode  31  along the wound cathode  31 . The uncoated portion  32   b  of the anode  32  is formed at the other end of the anode  32  along the wound anode  32 . The uncoated portions  31   b  and  32   b  are located at opposing ends of the electrode assembly  30 , respectively. 
         [0040]    For example, the case  35  is formed in an approximate cuboid so as to set a space for accommodating the electrode assembly  30  and an electrolyte solution therein, an opening for joining an outside space to an inside space is formed at one surface of the cuboid. The opening may permit the electrode assembly  30  to be inserted into the case  35 . 
         [0041]    The cap plate  40  is installed at the opening of the case  35  to substantially seal the case  35 . The case  35  and the cap plate  40  may be formed of aluminum, to facilitate welding of the case  35  to the cap plate  40 . 
         [0042]    Further, the cap plate  40  includes an electrolyte injection opening  49 , a vent hole  44 , and terminal holes H 1  and H 2 . The electrolyte injection opening  49  permits the electrolyte solution to be injected into the case  35  after the cap plate  40  is coupled to the case  35 . After injecting the electrolyte solution, the electrolyte injection opening  49  is sealed with a sealing stopper  47 . 
         [0043]    The vent hole  44  is sealed with a vent plate  45  so as to discharge internal pressure of the rechargeable battery  100 . When the internal pressure of the rechargeable battery  100  reaches predetermined pressure, the vent plate  45  is incised to open the vent hole  44 . The vent plate  45  has a notch  45   a  for inducing the incision. 
         [0044]    The cathode terminal  51  and the anode terminal  52  are installed at the terminal holes H 1  and H 2  of the cap plate  40 , and are electrically coupled to the electrode assembly  30 . That is, the cathode terminal  51  is electrically coupled to the cathode  31  of the electrode assembly  30 , and the anode terminal  52  is electrically coupled to the anode  32  of the electrode assembly  30 . Accordingly, the electrode assembly  30  is coupled to the outside of the case  35  through the cathode terminal  51  and the anode terminal  52 . 
         [0045]    The cathode terminal  51  and the anode terminal  52  are formed to have a similar structure or shape inside the cap plate  40 , so that the same structure will be described together. However, the cathode terminal  51  and the anode terminal  52  are formed to have different structures or shapes outside the cap plate  40 , so that the different structures will be separately described. 
         [0046]    The cathode and anode terminals  51  and  52  include rivet terminals  51   a  and  52   a  installed at or inserted into the terminal holes H 1  and H 2  of the cap plate  40 , respectively. Flanges  51   b  and  52   b  are wider than rivet terminals  51   a  and  52   a , respectively, and may be integrally formed with the respective rivet terminal  51   a  and  52   a  and enclosed by the cap plate  40  and the case  35 . Plate terminals  51   c  and  52   c  are formed externally with respect to the case  35  and the cap plate  40 , and may be coupled to the rivet terminals  51   a  and  52   a  by riveting or welding. 
         [0047]    Cathode and anode gaskets  36  and  37  are installed between the rivet terminals  51   a  and  52   a  of the cathode and anode terminals  51  and  52  and internal surfaces of the terminal holes H 1  and H 2  of the cap plate  40 , respectively, to substantially seal and electrically insulate spaces between the rivet terminals  51   a  and  52   a  of the cathode and anode terminals  51  and  52  and the cap plate  40 . 
         [0048]    The cathode and anode gaskets  36  and  37  further extend between the flanges  51   b  and  52   b  and the internal surface of the cap plate  40  to further seal and electrically insulate the spaces between the flanges  51   b  and  52   b  and the cap plate  40 . That is, the cathode and anode gaskets  36  and  37  prevent or reduce the electrolyte solution from being leaked through the terminal holes H 1  and H 2  after installing the cathode and anode terminals  51  and  52  in the cap plate  40 . 
         [0049]    Cathode and anode lead tabs  81  and  82  electrically couple the cathode and anode terminals  51  and  52  to the cathode and the anode  31  and  32  of the electrode assembly  30 . That is, the cathode and anode lead tabs  81  and  82  are coupled to lower ends of the rivet terminals  51   a  and  52   a  while being supported by the flanges  51   b  and  52   b  by coupling the cathode and anode lead tabs  81  and  82  to the lower ends of the rivet terminals  51   a  and  52   a  and caulking the lower ends. 
         [0050]    Cathode and anode insulating members  83  and  84  are installed between the cathode and anode lead tabs  81  and  82  and the cap plate  40  to electrically insulate the cathode and anode lead tabs  81  and  82  and the cap plate  40 . Further, one side of each of the cathode and anode insulating members  83  and  84  is coupled to the cap plate  40 , and the other side of each of the cathode and anode insulating members  83  and  84  surrounds the cathode and anode lead tabs  81  and  82 , the rivet terminals  51   a  and  52   a , and the flanges  51   b  and  52   b , to provide increased stability to a structure of the cathode and anode lead tabs  81 , the rivet terminals  51   a  and  52   a , and the flanges  51   b  and  52   b.    
         [0051]    In the meantime, a top plate  52   d  will be described in relation to a plate terminal  52   c  of the anode terminal  52 , and the external short part  60  will be described in relation to the plate terminal  52   c  of the cathode terminal  51 . 
         [0052]    The top plate  52   d  in the anode terminal  52  electrically couples the plate terminal  52   c  and the cap plate  40 . For example, the top plate  52   d  is interposed between the plate terminal  52   c  and the cap plate  40 , and permits a rivet terminal  52   a  to pass through. 
         [0053]    Accordingly, the top plate  52   d  and the plate terminal  52   c  are coupled to an upper end of the rivet terminal  52   a  by coupling the top plate  52   d  and the plate terminal  52   c  to the upper end of the rivet terminal  52   a  and caulking the upper end. The plate terminal  52   c  is installed outside the cap plate  40  with the top plate  52   d  interposed therebetween. 
         [0054]    The anode gasket  37  further extends between the rivet terminal  52   a  and the top plate  52   d . That is, the anode gasket  37  prevents the rivet terminal  52   a  and the top plate  52   d  from being directly electrically coupled to each other. That is, the top plate  52   d  is electrically coupled to the rivet terminal  52   a  through the plate terminal  52   c.    
         [0055]    As described above, the anode terminal  52  is electrically coupled to the cap plate  40  to charge the cap plate  40  and the case  35  with the anode. The cathode terminal  51  is electrically insulated or isolated from the cap plate  40  by interposing the insulator  70  therebetween. 
         [0056]      FIG. 3  is an exploded perspective view of a side of the cathode terminal  51 . Referring to  FIGS. 2 and 3 , the insulator  70  is located between the plate terminal  51   a  and the cap plate  40 , and surrounds an outer side of the plate terminal  51   c . The insulator  70  includes a fluid receiving recess  71  and an outlet  72 . 
         [0057]    The fluid receiving recess  71  is adjacent to a side of the cathode terminal  51  so as to induce and receive electrolyte fluid, for example, moisture, entering from the outside. The outlet  72  is connected from the fluid receiving recess  71  to the outside to discharge the received fluid to the outside of the insulator  70 . 
         [0058]    The fluid receiving recess  71  is formed adjacent to an outer circumference of the cathode terminal  51 , and particularly, is formed at a border surrounding the outer side or along a periphery of the plate terminal  51   c . The outlet  72  may be formed at both sides in a longitudinal direction of the cap plate  40  (left and right directions of  FIG. 2 ). 
         [0059]    The cathode terminal  51  is electrically insulated from the cap plate  40  by the insulator  70 , but may be electrically shorted with the cap plate  40  through the external short part  60 . 
         [0060]    In order to form the external short part  60 , the cap plate  40  includes a short hole H 3  under the cathode terminal  51 , and the plate terminal  51   c  of the cathode terminal  51  is formed so as to extend in a direction of the short hole H 3  away from the cap plate  40 . 
         [0061]    The external short part  60  includes a short protrusion  61  and a short member  62  separated or shorted according to internal pressure. The short protrusion  61  is formed at the plate terminal  51   c , so that the short protrusion  61  is separated or vertically offset with respect to the cap plate  40  by the insulator  70  and is therefore electrically insulated from the cap plate  40  by maintaining a state in which the short protrusion  61  is separated from the short member  62 . Accordingly, the cap plate  40  maintains a state in which the cap plate  40  is electrically insulated from the cathode terminal  51 . 
         [0062]    For example, the short protrusion  61  downwardly protrudes toward the short hole H 3  from the plate terminal  51   c , and the short member  62  is installed or located at the short hole H 3  to face the short protrusion  61 . That is, the short protrusion  61  and the short member  62  correspond to the short hole H 3 , and face each other to maintain a separated state (a solid line state), and form a short state (an imaginary line state) by reversal of the short member  62  when internal pressure of the rechargeable battery  100  increases, so that current charged in the electrode assembly  30  may be discharged. 
         [0063]    In the meantime, the plate terminal  51   c  of the cathode terminal  51  includes a first receiving recess G 1  (e.g., receiving recesses G 11  and G 12 ) in a surface facing the insulator  70 , and the insulator  70  includes a first wall B 1  (e.g., walls B 11  and B 12 ) protruding toward the first receiving recess G 1  to be inserted in the first receiving recess G 1 . The cap plate  40  includes a second receiving recess G 2  in a surface facing the insulator  70 , and the insulator  70  includes a second wall B 2  protruding toward the second receiving recess G 2  to be inserted in the second receiving recess G 2 . 
         [0064]    The fluid receiving recess  71  induces and receives electrolyte fluid entering from the outside and discharges the electrolyte fluid through the outlet  72 . In comparison, the first and second receiving recesses G 1  and G 2  and the first and second walls B 1  and B 2  increase the distance or length of a permeation path of the electrolyte fluid in order to reduce the permeation of the electrolyte fluid. The first receiving recess G 1  and the first wall B 1  increase the distance or length of the permeation path in an upper surface of the insulator  70 , and the second receiving recess G 2  and the second wall B 2  increase the distance or length of the permeation path in a lower surface of the insulator  70 . 
         [0065]    The first receiving recess G 1  includes an 11 th  receiving recess G 11  adjacent to an outer side of the rivet terminal  51   a  of the cathode terminal  51  and a 12 th  receiving recess G 12  adjacent to an outer side of the short protrusion  61 . The first wall B 1  includes an 11 th  wall protruding so as to be coupled to the 11 th  receiving recess G 11 , and a 12 th  wall B 12  protruding so as to be coupled to the 12 th  receiving recess G 12 . 
         [0066]    The 11 th  receiving recess G 11  and the 11 th  wall B 11  are coupled to each other to prevent or reduce the electrolyte fluid from permeating into the terminal hole H 1 . The 12 th  receiving recess G 12  and the 12 th  wall B 12  are coupled to each other to prevent or reduce the electrolyte fluid from permeating into the short hole H 3 . 
         [0067]    The second receiving recess G 2  and the second wall B 2  are adjacent to the outer side of the rivet terminal  51   a  of the cathode terminal  51 . Accordingly, the second receiving recess G 2  and the second wall B 2  are coupled with each other to prevent or reduce the electrolyte fluid from permeating into the terminal hole H 1 . 
         [0068]    The terminal hole H 1  at a side of the cathode terminal  51  forms a double electrolyte fluid blocking structure by the 11 th  receiving recess G 11  and the 11 th  wall B 11  in the upper surface of the insulator  70  and the second receiving recess G 2  and the second wall B 2  in the lower surface of the insulator  70 . Accordingly, it is possible to more effectively prevent or reduce corrosion of the cathode terminal  51 . 
         [0069]    Hereinafter, a second exemplary embodiment of the present invention will be described. A description of the same configuration as that of the first exemplary embodiment will be omitted, and a different configuration will be described. 
         [0070]      FIG. 4  is a cross-sectional view of a rechargeable battery  200  according to the second exemplary embodiment of the present invention. In the rechargeable battery  200  of the second exemplary embodiment, a cathode terminal  251  and an anode terminal  252  are electrically insulated from the cap plate  240 . 
         [0071]    To this end, an insulator  270  includes a first insulator  271  located between the cathode terminal  251  and the cap plate  240  and a second insulator  272  located between the anode terminal  252  and the cap plate  240 . 
         [0072]    The first insulator  271  is located between a plate terminal  251   c  and the cap plate  240  at a side of the cathode terminal  251 , and surrounds an outer side of the plate terminal  251   c . The second insulator  272  is located between a plate terminal  252   c  and the cap plate  240  at a side of the anode terminal  252 , and surrounds an outer side of the plate terminal  252   c.    
         [0073]    A fluid receiving recess  91  includes first and second fluid receiving recesses  711  and  712  formed at borders or along a periphery of the first and second insulators  271  and  272  surrounding outer sides of the plate terminals  251   c  and  252   c  of the cathode and anode terminals  251  and  252 , respectively. 
         [0074]    An outlet  92  includes first and second outlets  721  and  722  formed toward the outside at the first and second fluid receiving recesses  711  and  712 , respectively, so as to discharge the fluid received in the fluid receiving recess  91  to the outside of the first and second insulators  271  and  272 . 
         [0075]    The first receiving recess G 21  includes 21 st  and 22 nd  receiving recesses G 211  and G 212  formed in a surface of the plate terminals  251   c  and  252   c  of the cathode and anode terminals  251  and  252  facing toward the first and second insulators  271  and  272 . A first wall B 21  includes 21 st  and 22 nd  walls B 211  and B 212  formed in the first and second insulators  271  and  272  to be inserted in the 21 st  and 22 nd  receiving recesses G 211  and G 212 . 
         [0076]    The second receiving recess G 22  includes 23 rd  and 24 th  receiving recesses G 223  and G 224  formed in a surface of the cap plate  240  facing toward the first and second insulators  271  and  272 . The second wall B 22  includes 23 rd  and 24 th  walls B 223  and B 224  formed in the first and second insulators  271  and  272  in opposite sides of the 21 st  and 22 nd  walls B 211  and the B 212  to be inserted in the 23 rd  and 24 th  receiving recesses G 223  and G 224 . 
         [0077]    The coupling structures of the 21 st  and 22 nd  walls B 211  and B 212  and the 21 st  and 22 nd  receiving recesses G 211  and G 212  block or reduce the electrolyte fluid from permeating from the outsides of the first and second insulators  271  and  272 . The coupling structures of the 23 rd  and 24 th  walls B 223  and B 224  and the 23 rd  and 24 th  receiving recesses G 223  and G 224  block or reduce the electrolyte fluid from permeating from the insides of the first and second insulators  271  and  272 . 
         [0078]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents. 
       DESCRIPTION OF SOME OF THE REFERENCE SYMBOLS 
       [0079]      
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 30: Electrode assembly 
                 31: First electrode (cathode) 
               
               
                 31a, 32a: Coated portion 
                 31b, 32b: Uncoated portion 
               
               
                 32: Second electrode (anode) 
                 33: Separator 
               
               
                 35: Case 
                 36, 37: Cathode and anode gaskets 
               
               
                 40, 240: Cap plate 
                 44: Vent hole 
               
               
                 45: Vent plate 
                 47: Sealing stopper 
               
               
                 49: Electrolyte injection opening 
                   
               
               
                 51, 251: First electrode terminal (cathode terminal) 
                   
               
               
                 51a, 52a: Rivet terminal 
                 51b, 52b: Flange 
               
               
                 52, 252: Second electrode terminal (anode terminal) 
                   
               
               
                 51c, 52c, 251c, 252c: Plate terminal 
                   
               
               
                 52d: Top plate 
                 60: External short part 
               
               
                 61: Short protrusion 
                 62: Short member 
               
               
                 70, 270: Insulator 
                 71, 91: Fluid receiving recess 
               
               
                 72, 92: Outlet 
                 81, 82: Cathode and anode lead tabs 
               
               
                 83, 84: Cathode and anode insulating members 
                   
               
               
                 100, 200: Rechargeable battery 
                 271, 272: First and second insulators 
               
               
                 711, 712: First and second fluid receiving recesses 
                   
               
               
                 721: First outlet 
                 722: Second outlet 
               
               
                 B1, B2: First and second walls 
                 B11, B12: 11 th   and 12 th   walls 
               
               
                 B211, B212: 21 st   and 22 nd   walls 
                 B223, B224: 23 rd   and 24 th   walls 
               
               
                 G1, G21: First receiving recess 
                 G11, G12: 11 th   and 12 th   receiving recesses 
               
               
                 G2, G22: Second receiving recess  
                 G211, G212: 21 st   and 22 nd   receiving recesses 
               
               
                 G223, G224: 23 rd   and 24 th   receiving recesses 
                   
               
               
                 H1, H2: Terminal hole 
                 H3: Short hole