Abstract:
Provided is a plug that enables reliable and easy removal of a plug body together with a cover member from a tubular container without increasing an outwardly-bulging flange portion of a grip part of the plug body and is superior in productivity. A plug  1  for closing an open end of an open-ended tubular container  4 . A cover member  3  is fitted on a plug body  2  including a press-fit part  2   a  and a grip part  2   b . An engagement portion  3   d  is extended from a head plate  3   a  of the cover member  3  into a recess  2   d  in the upper surface of the plug body  2  to face an inside wall  2   e  surrounding the recess  2   d . When an external force is applied to incline the head plate  3   a  with respect to the upper surface of the plug body  2 , the engagement portion  3   d  is engaged to the inside wall  2   e.

Description:
TECHNICAL FIELD 
     This invention relates to a plug for closing open end of an open-ended tubular container, such as a blood collection tube, and particularly relates to a plug in which a cover member is fitted on a plug body made of rubber or the like. 
     BACKGROUND ART 
     Plugs made of rubber, elastomer or the like are conventionally used in order to seal bodily fluid collection tubes, such as a vacuum blood collection tube. 
     Patent Literature 1 below discloses an example of a plug of this kind.  FIG. 9( a )  is a partly cutaway front cross-sectional view for illustrating a plug described in Patent Literature 1. The plug  102  is attached to an upper end opening of a closed-bottomed, cylindrical, bodily fluid collection tube  101  to seal it. The plug  102  includes a plug body  103  made of rubber, elastomer or the like and a cover member  104 . The plug body  103  includes a press-fit part  103   a  press-fitted into the bodily fluid collection tube  101 ; and a grip part  103   b  continued upward from the press-fit part  103   a . The cover member  104  is fitted to the grip part  103   b  to cover the grip part  103   b.    
     The cover member  104  includes a head plate  104   a  engaging against the upper surface of the grip part  103   b  of the plug body  103 . A skirt  104   b  is provided to extend downward from the outer peripheral edge of the head plate  104   a.    
     Alternatively, Patent Literature 2 below discloses a plug  111  shown in front cross-section in  FIG. 10 . The plug  111  includes a plug body  112  made of rubber, elastomer or the like and a cover member  113  fitted on the plug body  112 . A press-fit part  112   a  of the plug body  112  is press-fitted into a bodily fluid collection tube  101 . A grip part  112   b  continued upward from the press-fit part  112   a  is covered by the cover member  113 . 
     An annular retaining ring  114  is placed on the upper surface of the grip part  112   b . The cover member  113  has a tubular shape. An annular extension  113   a  is provided to extend inward from the upper open edge of the cover member  113 . The retaining ring  114  is engaged to the annular extension  113   a  against slipping out upward. 
     The cover member  113  is provided at the middle of the height with an annular engagement ledge  113   b  extending inward from the inside wall of the cover member  113 . The annular engagement ledge  113   b  is clamped between the lower surface of the grip part  112   b  of the plug body  112  and the upper end of the bodily fluid collection tube  101 . Specifically, the grip part  112   b  is formed to have a larger diameter than the press-fit part  112   a  of the plug body  112 , so that a shoulder  112   c  is formed on the lower surface of the grip part  112   b . The annular engagement ledge  113   b  is engaged against this shoulder  112   c.    
     The cover members  104 ,  113  described in Patent Literatures 1 and 2 are provided to allow examining staffs to easily remove the plug bodies  103 ,  112  from the bodily fluid collection tubes  101  without touching the plug bodies  103 ,  112  with their hands. Specifically, by applying a force to the cover members  104 ,  113  with fingers to move it away upward from the bodily fluid collection tubes  101 , the plug bodies  103 ,  112  can be removed together with the cover members  104 ,  113  from the bodily fluid collection tubes  101 . 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP-B-4198309 
     Patent Literature 2: JP-B-3064444 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the plug  102  having such a configuration as described in Patent Literature 1 may cause a failure of removal of the plug body  103  together with the cover member  104 . Specifically, in removing the plug body  103 , as shown by the arrow in  FIG. 9( b ) , an external force is applied obliquely upward to the cover member  104  while the cover member  104  is twisted relative to the bodily fluid collection tube. When it is attempted to remove the plug body  103  from the bodily fluid collection tube  101  in the above manner, only the cover member  104  may be removed to leave the plug body  103  press-fitted in the bodily fluid collection tube  101 . Therefore, the examining staff or the like may have to remove the plug body  103  from the bodily fluid collection tube  101  with his/her fingers. Thus, the cover member  104  for preventing contagion may not be able to perform its intended function. 
     In order to solve the above problem, for example, it is conceivable to increase the area of a shoulder  103   c  located at the lower surface of the grip part  103   b  in  FIG. 9( a ) . In this case, however, the shoulder  103   c  upward of the press-fit part  103   a  must be increased in outside diameter. In other words, the volume of a flange portion of the grip part  103   b  bulging outward beyond the press-fit part  103   a  (and thus the grip part volume) must be increased. This presents a problem of increased volume of the plug body  103 , resulting in increased medical waste. 
     On the other hand, in the plug  111  having such a configuration as described in Patent Literature 2, the annular engagement ledge  113   b  is engaged against the annular shoulder  112   c  of the plug body  112 . Therefore, even when an external force is applied obliquely upward to the cover member  113  while the cover member  113  is twisted relative to the bodily fluid collection tube  101 , the annular engagement ledge  113   b  is held engaged state against the shoulder  112   c . As a result, the plug body  112  can be reliably removed together with the cover member  113  from the bodily fluid collection tube  101 . 
     However, the plug  111  is composed of three members: the plug body  112 , the cover member  113 , and the retaining ring  114 . Therefore, there arises a problem in that the number of elements is large, which makes the assembly process complicated. In addition, during assembly, the annular extension  113   a  for engaging the retaining ring  114  may be broken so that the retaining ring  114  may slip out. This presents another problem of low productivity. 
     An object of the present invention is to provide a plug that can eliminate the above disadvantages of the conventional techniques, enables easy and reliable removal of a plug body together with a cover member from an open end of a tubular container without increasing the volume of the above-mentioned flange portion of the plug body, i.e., the grip part volume, has a small number of elements, can be easily assembled, and is superior in productivity. 
     Solution to Problem 
     The present invention is a plug for closing an open end of an open-ended tubular container. The plug of the present invention includes a plug body and a cover member. The plug body includes: a press-fit part to be press-fitted into the open end of the tubular container; and a grip part continuous with the top of the press-fit part and having a larger diameter than the press-fit part, wherein an upper surface of the grip part has a recess formed therein and surrounded by an inside wall extending downward. The cover member includes a head plate and a skirt extending downward from a peripheral edge of the head plate and is fitted on the plug body so that a lower surface of the head plate and the upper surface of the grip part of the plug body face each other. 
     In the plug according to the present invention, an engagement portion provided at the head plate of the cover member and engaged to the inside wall surrounding the recess of the entire plug is extended from the head plate of the cover member to the interior of the recess to face a surface of the inside wall surrounding the recess of the plug body. 
     In a particular aspect of the plug according to the present invention, the engagement portion is engaged against the inside wall surrounding the recess of the plug body. In this case, since the engagement portion of the cover member is engaged against the inside wall of the plug body, an external force applied to the cover member is immediately applied also to the inside wall of the plug body. Therefore, the plug body can be more reliably removed together with the cover member. 
     In another particular aspect of the plug according to the present invention, at least a portion of an inside surface of the head plate of the cover member is engaged against the upper surface of the grip part of the plug body. In this case, since no gap exists between the inside surface of the head plate and the upper surface of the grip part, the dimension of the plug in the height direction can be reduced. 
     In still another particular aspect of the plug according to the present invention, the inside wall surrounding the recess of the plug body is an annular inside wall and the engagement portion includes a curved surface portion having a shape fitting the annular inside wall. In this case, even when an external force is applied obliquely upward to the cover member while the cover member is twisted relative to a bodily fluid collection tube, the force can be immediately applied through the engagement portion to the annular inside wall of the grip part. Thus, the plug body can be more reliably removed together with the cover member. Preferably, the engagement portion has a cylindrical shape. In this case, the plug body can be still more reliably removed together with the cover member. 
     In still another particular aspect of the plug according to the present invention, an outer peripheral edge of the grip part of the plug body is located below an outer peripheral edge of the recess in the grip part to thus create a space between the head plate of the cover member and the upper surface of the plug body, and the head plate of the cover member is provided at a portion thereof facing the space with a rib extending downward from the head plate and engaging against the upper surface of the grip part of the plug body. In this case, since the space is created between the head plate of the cover member and the upper surface of the plug body but the rib is provided, the plug body can be reliably removed together with the cover member from the tubular container. 
     In still another particular aspect of the plug according to the present invention, the upper surface of the grip part of the plug body is an inclined surface gradually lowering from the outer peripheral edge of the recess toward the outer peripheral edge of the grip part and the rib is provided to engage against the inclined surface. In this manner, by providing the rib so that also when the upper surface of the grip part is the inclined surface, the rib engages against the inclined surface, the plug body can be reliably removed together with the cover member from the tubular container. 
     Advantageous Effects of Invention 
     In the plug according to the present invention, since the cover member is provided with the engagement portion described above and the engagement portion is extended from the head plate of the cover member to the interior of the recess of the plug body to face the surface of the inside wall surrounding the recess, the engagement portion is engaged to the inside wall of the plug body when an external force is applied to incline the head plate of the cover member with respect to the upper surface of the plug body or an external force is applied obliquely upward while the cover member is twisted relative to a bodily fluid collection tube. Therefore, in removing the cover member, the plug body can be easily and reliably removed together with the cover member from the open end of the tubular container. Furthermore, without increasing the volume of the flange portion of the plug body, the plug body can be reliably removed together with the cover member from the tubular container in the above manner. Therefore, this can reduce the cost of the plug body and reduce medical waste. In addition, it suffices if the plug includes the plug body and the cover member, and there is no need for such a retaining ring as described in Patent Literature 2 and for any complicated structure for engaging the retaining ring. Therefore, the number of elements can be reduced and the assembly process can be simplified. Hence, a plug can be provided which is superior in productivity and inexpensive. 
     The present invention enables the examining staff or the like to reliably remove the plug body together with the cover member simply by applying an external force to the cover member without touching the plug body with his/her fingers. Therefore, the risks of contagion and the like of the examining staff can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1( a )  is a front cross-sectional view of a plug according to a first embodiment of the present invention,  FIG. 1( b )  is a partly cutaway front cross-sectional view showing a state that the plug shown in  FIG. 1( a )  is attached to a tubular container, and  FIG. 1( c )  is a front cross-sectional view showing a modification of the plug. 
         FIG. 2( a )  is a front view of a plug body used in the first embodiment of the present invention and  FIG. 2( b )  is a front cross-sectional view thereof. 
         FIG. 3( a )  is a plan view of a cover member used in the plug of the first embodiment of the present invention and  FIG. 3( b )  is a front cross-sectional view thereof. 
         FIG. 4  is a front cross-sectional view for illustrating a plug according to a second embodiment of the present invention. 
         FIGS. 5( a ) and 5( b )  are a front view and a front cross-sectional view of a plug body used in the second embodiment. 
         FIG. 6( a )  is a plan view of a cover member used in the plug of the second embodiment of the present invention,  FIG. 6( b )  is a front cross-sectional view thereof, and  FIG. 6( c )  is a bottom view thereof. 
         FIG. 7  is a front cross-sectional view showing a plug of a first comparative example. 
         FIG. 8  is a front cross-sectional view showing a plug of a second comparative example. 
         FIG. 9( a )  is a partly cutaway front cross-sectional view showing a state that a conventional plug is attached to a tubular container and  FIG. 9( b )  is a front cross-sectional view for illustrating a problem of the conventional plug. 
         FIG. 10  is a partly cutaway front cross-sectional view for illustrating a state that another example of a conventional plug is attached to a tubular container. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present invention will become apparent by explaining specific embodiments of the present invention with reference to the drawings. 
       FIG. 1( a )  is a front cross-sectional view showing a plug according to a first embodiment of the present invention and  FIG. 1( b )  is a partly cutaway front cross-sectional view showing a state that the plug is attached to a tubular container. 
     The plug  1  includes a plug body  2  and a cover member  3 . Therefore, the plug  1  is composed of the two members. 
     As shown in  FIG. 1( b ) , the plug  1  is attached to a tubular container  4  to seal an opening  4   a  located at the upper end of the tubular container  4 . The tubular container  4  is a closed-bottomed, cylindrical container having an opening  4   a  at the upper end thereof. By attaching the plug  1  to the tubular container  4  under reduced pressure, a vacuum blood collection tube is constructed. However, the tubular container  4  may be any bodily fluid collection container for collecting various bodily fluids, not only the blood collection tube. 
     The plug body  2  is made of an elastic material, such as rubber or elastomer. 
     As shown in  FIGS. 2( a ) and 2( b ) , the plug body  2  includes a press-fit part  2   a  and a grip part  2   b  continued upward from the press-fit part  2   a . The press-fit part  2   a , as shown in  FIG. 1( b ) , is a portion to be press-fitted into the interior of the tubular container  4 . Since the tubular container  4  is cylindrically tubular, the press-fit part  2   a  has a cylindrical shape. However, the shape of the press-fit part  2   a  can be changed depending upon the shape of the tubular container  4 . 
     The grip part  2   b  has a larger diameter than the press-fit part  2   a . Since, therefore, the grip part  2   b  bulges outward beyond the press-fit part  2   a , an annular shoulder  2   c  is formed on the lower surface of the grip part  2   b.    
     As shown in  FIG. 2( b ) , a recess  2   d  is formed to open into the upper surface of the grip part  2   b , i.e., the upper surface of the plug body  2 . The recess  2   d  is surrounded by a cylindrical inside wall  2   e  continuous with the upper surface of the grip part  2   b . Note that in this embodiment the recess  2   d  is extended downward beyond the inside wall  2   e . More specifically, a lower portion  2   d   2  of the recess  2   d  is provided which has a smaller diameter than an upper portion  2   d   1  thereof surrounded by the inside wall  2   e . At the junction between the upper portion  2   d   1  and the lower portion  2   d   2 , an annular inclined surface  2   f  is provided to gradually reduce the diameter downward. 
     On the other hand, the press-fit part  2   a  of the plug body  2  has a recess  2   g  formed to open into the lower surface thereof. Since the recess  2   d  and the recess  2   g  are formed, a thin-walled portion  2   h  is formed between the recess  2   d  and the recess  2   g . The thin-walled portion  2   h  is a portion to be pierced through by a vacuum blood collection needle. Since the thickness of the thin-walled portion  2   h  is smaller than that of the plug body  2 , the thin-walled portion  2   h  can be easily pierced through by a vacuum blood collection needle. 
     Although in this embodiment not only the upper portion  2   d   1  surrounded by the inside wall  2   e  but also the lower portion  2   d   2  are provided, the lower portion  2   d   2  may not be provided. In other words, the thin-walled portion  2   h  may be located just below the upper portion  2   d   1 . 
     However, the lower portion  2   d   2  is preferably provided, which makes the thickness of the thin-walled portion  2   h  smaller. Thus, the resistance to piercing can be reduced. 
     The annular inside wall  2   e  has a cylindrical shape. Therefore, the annular inside wall  2   e  surrounds the recess  2   d  and extends in a vertical direction. 
     In this embodiment, the cover member  3  is formed of a synthetic resin molded article. However, the cover member  3  may be made of metal or other materials. 
     As shown in  FIGS. 3( a ) and 3( b ) , the cover member  3  includes a head plate  3   a  and a skirt  3   b  integrally provided with the head plate  3   a  to extend downward from an outer peripheral edge of the head plate  3   a . In this embodiment, the outer peripheral edge of the head plate  3   a  has a circular shape. Therefore, the cover member  3  has an approximately cylindrical shape. 
     When attached to the tubular container  4 , as shown in  FIG. 1( b ) , the skirt  3   b  covers the plug body  2  and also covers an upper portion of the outside wall of the tubular container  4 . The cover member  3  is provided in order to prevent the fingers of the examining staff from touching the opening  4   a  of the tubular container  4  and the plug body  2 . 
     A circular opening  3   c  is formed in the center of the head plate  3   a . An annular engagement portion  3   d  extending downward from the open edge of the opening  3   c  is provided continuously with the head plate  3   a . In this embodiment, the engagement portion  3   d  has a cylindrical shape. However, the engagement portion  3   d  may be formed of a plurality of curved surface portions obtained by segmenting a cylindrical curved surface. 
     The engagement portion  3   d  extends in a vertical direction. Furthermore, an annular shoulder  3   e  is formed on the inner peripheral surface of the cover member  3 . The inside diameter of a portion of the cover member  3  upward of the annular shoulder  3   e  is set at a diameter that allows the grip part  2   b  of the plug body  2  to be inserted thereinto. Specifically, the inside diameter of the portion of the cover member  3  upward of the annular shoulder  3   e  is equal to the outside diameter of the grip part  2   b  but may be slightly smaller than the outside diameter of the grip part  2   b  so long as the grip part  2   b  can be press-fitted into it. Alternatively, the inside diameter of the portion upward of the annular shoulder  3   e  may be larger than the outside diameter of the grip part  2   b . In this case, when the cover member  3  is fitted on the plug body  2 , a clearance will be created between the outer peripheral surface of the grip part  2   b  and the inner peripheral surface of the cover member  3 , which may cause backlash. Preferably, it is desired that the inside diameter of the portion of the cover member  3  upward of the annular shoulder  3   e  be engaged against the outer peripheral surface of the grip part  2   b  to create no clearance therebetween. 
     When the cover member  3  is fitted on the plug body  2 , the annular shoulder  3   e  engages the shoulder  2   c  located at the lower surface of the grip part  2   b  as shown in  FIG. 1( a ) , which prevents the plug body  2  from slipping out downward. 
     As shown in  FIG. 1( a ) , by inserting the plug body  2  into the cover member  3 , in other words, by fitting the cover member  3  on the plug body  2 , the cover member  3  can be locked to the plug body  2 . In this state, the upper surface of the grip part  2   b  of the plug body  2  and the inside surface of the head plate  3   a  of the cover member  3  face each other in parallel relation and with a gap therebetween. However, such a gap may not be provided. Specifically, as in a modification shown in  FIG. 1( c ) , the upper surface of the plug body  2  may be engaged against the inside surface of the head plate  3   a.    
     Furthermore, in  FIG. 1( a )  of this embodiment, the length H 2  as a vertical dimension of the engagement portion  3   d  shown in  FIG. 3( b )  is set larger than the vertical dimension H 1  of the inside wall  2   e  of the plug body  2  shown in  FIG. 2( b ) . Therefore, the above-mentioned gap is created between the inside surface of the head plate  3   a  and the upper surface of the grip part  2   b . And, as shown in  FIG. 1( a ) , the distal end of the engagement portion  3   d  abuts against a portion of the plug body extending continuously from the lower end of the inside wall  2   e.    
     The outside diameter of the engagement portion  3   d  is set approximately equal to the inside diameter of the recess defined by the inside wall  2   e . Therefore, the outer peripheral surface of the engagement portion  3   d , which is a cylindrically curved surface, faces and engages against the inside wall  2   e.    
     However, the outer peripheral surface of the engagement portion  3   d  may face the inside wall  2   e  with a gap therebetween, as in a second embodiment to be described hereinafter and shown in  FIG. 4 . Preferably, it is desired that, as in the embodiment shown in  FIG. 1 , the outer peripheral surface of the engagement portion  3   d  be engaged against the inside wall  2   e . In this case, even when upon removal an external force is applied obliquely upward to the cover member  3  while the cover member  3  is twisted relative to the bodily fluid collection tube, the force is immediately applied through the engagement portion to the inside wall  2   e  of the plug body  2 . Thus, upon the removal to be described hereinafter, the plug body  2  and the cover member  3  can be unitarily and easily removed. 
     The plug  1  of this embodiment, as shown in  FIG. 1( b ) , is attached to the opening  4   a  of the tubular container  4  to seal it. In use, for example, blood or the like is collected into the tubular container  4  using a vacuum blood collection needle. Next, to conduct a blood test or the like, the plug  1  is removed from the tubular container. In this removal, a portion of the skirt  3   b  of the cover member  3  is grasped with fingers and an external force is applied obliquely upward to the cover member  3  while the cover member  3  is twisted relative to the bodily fluid collection tube. Thus, the cover member  3  is removed together with the plug body  2  from the tubular container  4 . In this case, even if the head plate  3   a  of the cover member  3  is urged to incline with respect to the upper surface of the plug body  2 , the engagement portion  3   d  comes into close contact with the inside wall  2   e  to prevent the head plate  3   a  from moving away from the upper surface of the plug body  2 . In other words, the engagement portion  3   d  is engaged to the inside wall  2   e  to avoid separation of the cover member  3  from the plug body  2 . The plug body  2  can be thus easily removed together with the cover member  3  from the tubular container. 
     In addition, since, as described previously, the plug  1  is composed of two members: the plug body  2  and the cover member  3 , it is prevented from increase in number of elements. Furthermore, the cover member  3  has a relatively simple structure in which the head plate  3   a  is provided with the engagement portion  3   d . Therefore, the cover member  3  can be easily molded and easily fitted to the plug body  2 . As a result, the cost can be reduced to increase the productivity. 
       FIG. 4  is a front cross-sectional view showing a plug  11  according to a second embodiment of the present invention. A cover member  13  is fitted on a plug body  12 . The plug  11  has substantially the same configuration as the plug  1  of the first embodiment except that the plug body  12  has an inclined surface  2   i  formed on the upper surface of the grip part  2   b  and that the cover member  13  includes ribs  3   g  provided on the inside surface of the head plate  3   a . Therefore, like parts bear the same references and further explanation thereof will be accordingly omitted. 
     As shown in  FIGS. 5( a ) and 5( b ) , the height of the upper surface of the grip part  2   b  gradually decreases radially outward from the outer peripheral edge of the recess  2   d  provided in the upper surface of the plug body  2 , so that an annular inclined surface  2   i  is formed on the upper surface of the grip part  2   b.    
     Thus, as shown in  FIG. 4 , a space is created between the inclined surface  2   i  and the inside surface of the head plate  3   a  of the cover member  13 . To prevent backlash due to this space, a plurality of ribs  3   g  are formed on the inside surface of the head plate  3   a  of the cover member  13 . 
     As shown in  FIGS. 6( a ) to 6( c ) , the cover member  13  includes the head plate  3   a  and the plurality of ribs  3   g  to be located in the space are formed on the inside surface of the head plate  3   a . In this embodiment, the plurality of ribs  3   g  extend in the radial direction of the head plate  3   a . Furthermore, the under surfaces of the ribs  3   g  are formed in inclined surfaces  3   g   1  gradually lowering from radially inner portion toward outer portion of the head plate  3   a . These inclined surfaces  3   g   1  have a gradient equal to that of the inclined surface  2   i  of the plug body  2 . And, when the cover member  13  is fitted on and locked to the plug body  12 , the inclined surfaces  3   g   1  at the under surfaces of the ribs  3   g  engage against the inclined surface  2   i  of the plug body  2 . Thus, with the plug body  12  locked to the cover member  13 , the position of the plug body  12  can be stably retained. In this manner, if the plug body  2  has an inclined surface  2   i , it is preferred that the above ribs  3   g  be provided integrally on the inside surface of the head plate  3   a  of the cover member  3 . 
     As shown in  FIG. 6( c ) , the plurality of ribs  3   g  are distributed at regular intervals in the circumferential direction of the head plate  3   a . No particular limitation is placed on the number of the plurality of ribs  3   g  and any plurality of ribs  3   g  may be provided. Alternatively, a single rib may be provided the whole of which continues in an integral, thick-walled form. 
     However, preferably, it is desired to provide a plurality of ribs  3   g , which can stabilize a state that the plug body  12  is fitted to the cover member  13 . 
     Furthermore, the provision of a plurality of ribs  3   g  are preferably such that the angles formed by connecting the center of the head plate  3   a  and the ribs become equal to one another. Thus, variations of the position of the plug body  12  can be reduced. 
     Also when it is attempted to remove the plug  11  of this embodiment from the state where it is attached to the tubular container by applying an external force to the skirt  3   b  of the cover member  13 , the engagement portion  3   d  engages against the inside wall  2   e . Therefore, the plug body  12  can be easily and reliably removed together with the cover member  13  from the tubular container. 
     Next, a description will be given of specific experimental examples. 
     Example 1 
     The plug  1  shown in  FIG. 1( a )  was prepared. The plug body  2  used was one made of butyl rubber. The dimensions of the plug body  2  are as follows. 
     The outside diameter of the press-fit part  2   a:  11 mm 
     The outside diameter of the grip part  2   b:  15 mm 
     The thickness of the grip part  2   b:  3 mm 
     The volume of the grip part  2   b  was 0.40 cm 3 . The opening diameter of the recess  2   d , i.e., the diameter of a portion thereof surrounded by the inside wall  2   e , was 10 mm. 
     A molded article made of a polyethylene-based synthetic resin was prepared as the cover member  3 . In the cover member  3 , the outside diameter of the engagement portion  3   d  in the head plate  3   a  was 9 mm. The dimension H 2  from the inside surface of the head plate  3   a  to the lower end of the engagement portion  3   d  was 2 mm. Furthermore, the dimension H 1  of the inside wall  2   e  of the plug body  2  in the height direction was 1.3 mm. 
     Example 2 
     In the plug body  12 , the angle α of inclination of the inclined surface  2   i  shown in  FIG. 5( b )  was 26 degrees, the outside diameter of the press-fit part  2   a  was 11 mm, and the maximum outside diameter of the grip part  2   b  was 15 mm. Furthermore, the dimension H 1  of the inside wall  2   e  in the height direction was 1.3 mm like Example 1. 
     The outside diameter of the head plate  3   a  of the cover member  13  was 16 mm and the length from the inside surface of the head plate  3   a  to the lower end of the engagement portion  3   d  was 2 mm. 
     The opening diameter of the recess  2   d , i.e., the diameter of a portion thereof surrounded by the inside wall  2   e , was 10 mm. The volume of the grip part  2   b  was 0.36 cm 3 . 
     Comparative Example 1 
     The plug  121  shown in  FIG. 7  was prepared as Comparative Example 1. In Comparative Example 1, the plug body  122  used was one including a press-fit part  122   a  with a cylindrical outside diameter of 11 mm and a grip part  122   b  with a cylindrical outside diameter of 15 mm. The upper surface of the plug body  122  had a recess  122   c  formed therein. 
     On the other hand, the cover member  123  used was one having the same configuration as the cover member  104  shown in  FIG. 9( a ) . In this case, the volume of the grip part was 1.10 cm 3 . 
     Comparative Example 2 
     The plug  131  shown in  FIG. 8  was prepared as Comparative Example 2. The plug  131  of Comparative Example 2 had the same configuration as the plug  121  of Comparative Example 1. However, the volume of the grip part was 0.60 cm 3 . 
     Evaluation of Examples and Comparative Examples 
     Each plug was attached to a 7-mL volume, closed-bottomed, tubular container the upper end opening of which had an opening diameter of 10.7 mm. Thereafter, it was attempted to remove the cover member together with the plug body from the tubular container by grasping the skirt of the cover member with the hand, applying a force obliquely upward to the cover member while twisting it relative to the bodily fluid collection tube, and thus pushing up the cover member  3 . For ten tubular containers, the above plug removal was attempted. Table 1 below shows the number of tubular containers for which the cover member was disengaged from the plug body and only the cover member was removed from the tubular container, resulting in failure to remove the plug body together with the cover member. 
     Table 1 also shows the volumes of the grip parts of the plug bodies. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Number of Containers for 
                   
               
               
                   
                   
                 which Cover Member was 
                 Grip Part Volume 
               
               
                   
                   
                 Disengaged from Plug Body 
                 (cm 3 ) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Ex. 1 
                 0 
                 0.40 
               
               
                   
                 Ex. 2 
                 0 
                 0.36 
               
               
                   
                 Comp. Ex. 1 
                 1 
                 1.10 
               
               
                   
                 Cornp. Ex. 2 
                 10 
                 0.60 
               
               
                   
                   
               
             
          
         
       
     
     As is evident from Table 1, in Comparative Example 1 and Comparative Example 2, there were cases where only the cover member was detached. Particularly in Comparative Example 2 in which the grip part of the plug body was decreased in volume from 1.10 cm 3  to 0.60 cm 3 , size reduction could be achieved but, in all the cases of the ten tubular containers, only the cover member was detached. 
     In contrast, in Examples 1 and 2, the grip parts of the plug bodies were decreased in volume to 0.40 cm 3  and 0.36 cm 3 , respectively, but nevertheless the plug bodies could be reliably removed together with the cover members. 
     Therefore, in Examples 1 and 2, the volume of the grip part of the plug body can be decreased to approximately 40% of that in Comparative Example 1. Hence, it can be seen that the amount of waste after the collection of bodily fluid can be reduced to reduce environmental burden. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  . . . plug 
               2  . . . plug body 
               2   a  . . . press-fit part 
               2   b  . . . grip part 
               2   c  . . . annular shoulder 
               2   d  . . . recess 
               2   e  . . . inside wall 
               2   f  . . . annular inclined surface 
               2   g  . . . recess 
               2   h  . . . thin-walled portion 
               2   i  . . . inclined surface 
               3  . . . cover member 
               3   a  . . . head plate 
               3   b  . . . skirt 
               3   c  . . . opening 
               3   d  . . . engagement portion 
               3   e  . . . annular shoulder 
               3   g  . . . rib 
               3   g   1  . . . inclined surface 
               4  . . . tubular container 
               4   a  . . . opening 
               11  . . . plug 
               12  . . . plug body 
               13  . . . cover member 
               101  . . . bodily fluid collection tube 
               102  . . . plug 
               103  . . . plug body 
               103   a  . . . press-fit part 
               103   b  . . . grip part 
               103   c  . . . annular shoulder 
               104  . . . cover member 
               104   a  . . . head plate 
               104   b  . . . skirt 
               111  . . . plug 
               112  . . . plug body 
               112   a  . . . press-fit part 
               112   b  . . . grip part 
               112   c  . . . shoulder 
               113  . . . cover member 
               113   a  . . . annular extension 
               113   b  . . . annular engagement ledge 
               114  . . . ring 
               121  . . . plug 
               122  . . . plug body 
               122   a  . . . press-fit part 
               122   b  . . . grip part 
               122   c  . . . recess 
               123  . . . cover member 
               131  . . . plug 
               132  . . . plug body 
               132   a  . . . press-fit part 
               132   b  . . . grip part