Patent Publication Number: US-8523003-B2

Title: Resin container

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims to the benefit of priority to Japanese Patent Application No. 2011-235555 filed on Oct. 27, 2011, of which full contents are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a resin container which accommodates liquid. 
     2. Description of the Related Art 
     When liquid such as an industrial drug is accommodated in a resin container which is integrally molded into a drum shape by blow molding so as to be stored or conveyed, a pipe is used for discharging the liquid in some cases. Conventionally, as illustrated in  FIG. 5A , a pipe  150  of which one end is attached to an outlet port  125  provided on a ceiling plate  120  of a resin container  100  is lowered straightly toward a bottom plate  110  so that liquid is discharged. A method of discharging the liquid is classified broadly into a method of connecting a pump to the pipe to suck the liquid (hereinafter, referred to as “suction system”) and a method of feeding the air into the container and pressurizing the liquid to push out the liquid through the pipe (hereinafter, referred to as “pressure feeding system”). 
     Irregularities are formed on the bottom plate of the resin container which is integrally molded normally. Therefore, in the conventional resin container, there has been a problem that liquid present on a portion of a recessed surface, which is separated from a position of a lower end of the pipe due to a protruding portion, is not discharged and is left. A height of the irregularities on the bottom plate of a common resin container is not so high. However, as a capacity of the container is increased, an area of the bottom plate is increased so that a volume of residual liquid is also increased. For example, in the conventional resin container having a capacity of 200 liters, a residual liquid amount when the liquid is discharged with the suction system is as large as equal to or larger than 1.5 liters. 
     Further, when the liquid is discharged with the pressure feeding system, as illustrated in  FIG. 5B , the bottom plate  120  expands outward with increase of a pressure in the resin container  100  so that the lower end of the pipe  150  is distanced from the bottom plate  110 . In addition, the ceiling plate  120  also expands outward and the outlet port  125  is inclined. With this, the pipe  150  is inclined so that the lower end of the pipe  150  is largely distanced from the bottom plate  110  further. Therefore, in the case of the pressure feeding system, the liquid cannot be discharged at a time when the liquid level becomes lower than the lower end of the pipe  150  with the discharge of the liquid. Therefore, the residual liquid amount is large. For example, in the conventional resin container having a capacity of 200 liters, the residual liquid amount when the liquid is discharged with the pressure feeding system is as large as approximately 5 liters. 
     The liquid which has not been discharged from the resin container and has been left is to be discarded and is wasteful as resource. Further, there are a number of extremely expensive liquids among the industrial drugs. Therefore, a technique of reducing a residual liquid amount has been desired in terms of reduction in cost. 
     SUMMARY OF THE INVENTION 
     In view of the above circumstances, an object of the present invention is to provide a resin container which can reduce an amount of liquid which is not discharged and is left. 
     In order to achieve the above-described object, a resin container according to an aspect of the invention “includes a main body in which a bottom plate, a cylindrical body portion erected from an outer circumference of the bottom plate, and a ceiling plate closing an upper end of the body portion are integrally molded, and a pipe which is inserted into the main body through an outlet port opened on the ceiling plate, wherein the main body includes a recessed portion which is formed on the bottom plate in a recessed form and of which center is not located on a virtual axis line extending from a center of the outlet port in a container height direction, and a gutter-shaped groove portion which is formed on the bottom plate and reaches the recessed portion, and the pipe is curved from an upper end to a lower end, the lower end of the pipe is pressed against a boundary between an inner circumferential surface of the recessed portion at a side opposite to a side of the outlet port and a bottom surface of the recessed portion”. 
     The center of the recessed portion is not located on the virtual axis line extending from the center of the outlet port in the container height direction. Therefore, the recessed portion is not located just under the outlet port. Further, the pipe which is sufficiently loner than a height (inner dimension) of the resin container is employed such that the pipe is curved from the outlet port toward the recessed portion. 
     A tensile force acts on the pipe having an extra length for a curved amount between the outlet port and the recessed portion. Therefore, the lower end of the pipe is pressed against the boundary between the inner circumferential surface of the recessed portion (hereinafter, referred to as “opposite-side inner circumferential surface” in some cases) at the side opposite to the side of the outlet port and the bottom surface of the recessed portion. Further, even when the ceiling plate and the bottom plate expand when the liquid is discharged with the pressure feeding system, the state where the lower end of the pipe is pressed against the boundary (hereinafter, referred to as “opposite-side boundary portion” in some cases) between the opposite-side inner circumferential surface and the bottom surface of the recessed portion is kept since the pipe has the extra length. 
     Accordingly, in the aspect of the invention with the above-mentioned configuration, even when the ceiling plate and the bottom plate expand, the lower end of the pipe stops at the opposite-side boundary portion of the recessed portion all the time. Further, at a final stage of processing of discharging the liquid, the liquid which has been reduced is collected to the recessed portion as a lower portion on the bottom plate. 
     In addition, the groove portion reaching the recessed portion is formed on the bottom plate. Therefore, even when the bottom plate has the irregularities and a recessed surface separated from a position of the lower end of the pipe due to the protruding portion is present, the liquid on the recessed surface is easy to flow into the recessed portion through the groove portion. 
     Then, almost total amount of liquid in the recessed portion is discharged through the pipe of which lower end is located at the opposite-side boundary portion. This makes it possible to discharge almost total amount of the liquid in the resin container. Therefore, the residual liquid amount can be largely reduced in comparison with the conventional technique. 
     In the resin container according to the aspect of the invention, it is preferable that “the recessed portion be formed on a center of the bottom plate” in the above-described configuration. 
     In the aspect of the invention, a configuration in which the center of the recessed portion is not located on the virtual axis line extending from the center of the outlet port in the container height direction is employed. Therefore, in the configuration in which the recessed portion is located at the center of the bottom plate, the outlet port is provided at a position which is eccentric on the ceiling plate. 
     The recessed portion is a lower portion on the bottom plate and is a portion on which liquid remains till the final stage when the liquid is discharged. The recessed portion is located at the center of the bottom plate so that a preferable balance of the resin container is realized and a posture thereof is stable. 
     In the resin container according to the aspect of the invention, it is preferable that “the main body further include an annular portion which is provided so as to project downward from the outer circumference of the bottom plate to a height lower than the bottom surface of the recessed portion” in the above-described configuration. 
     The resin container with the configuration is grounded at the annular portion in a state where at least the bottom plate does not expand. With this, the posture of the resin container is stable in comparison with a case where the resin container is grounded at the bottom surface of the recessed portion. 
     As described above, as an effect of the invention, a resin container which can reduce an amount of liquid which is not discharged and is left can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional front view illustrating a resin container according to one embodiment of the invention. 
         FIG. 2  is a partial cross-sectional front view illustrating the resin container in  FIG. 1  when an inner pressure is increased. 
         FIG. 3  is a plan view illustrating the resin container in  FIG. 1 . 
         FIG. 4  is a perspective view illustrating a vicinity of a bottom plate of the resin container in  FIG. 1 . 
         FIG. 5A  is a partial cross-sectional front view for explaining discharge of liquid in a conventional resin container, and  FIG. 5B  is a partial cross-sectional front view for explaining discharge of the liquid in the conventional resin container when an inner pressure is increased. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, a resin container  1  as one embodiment of the invention is described with reference to  FIG. 1  to  FIG. 4 . The resin container  1  includes a main body  10  and a pipe  71 . A bottom plate  20 , a cylindrical body portion  30 , and a ceiling plate  40  are integrally molded in the main body  10 . The body portion  30  is erected from an outer circumference of the bottom plate  20 . The ceiling plate  40  closes an upper end of the body portion  30 . The pipe  71  is inserted into the main body  10  through an outlet port  45  opened on the ceiling plate  40 . In the configuration, the main body  10  includes a recessed portion  50  and gutter-shaped groove portions  60 . The recessed portion  50  is formed on the bottom plate  20  in a recessed form and a center of the recessed portion  50  is not located on a virtual axis line X extending from a center of the outlet port  45  in the container height direction. The groove portions  60  are formed on the bottom plate  20  and reach the recessed portion  50 . The pipe  71  is curved from an upper end to a lower end, the lower end of the pipe  71  is pressed against a boundary (opposite-side boundary portion  55 ) between an inner circumferential surface  52  of the recessed portion  50  at a side opposite to a side of the outlet port  45  and a bottom surface  51  of the recessed portion  50 . 
     As will be described more in detail, the main body  10  is integrally molded by blow molding of a thermoplastic resin such as polyethylene. The main body  10  includes a lower annular portion  27  and an upper annular portion  47  in addition to the above-described configuration. The lower annular portion  27  is provided so as to project downward from the outer circumference of the bottom plate  20 . The upper annular portion  47  is provided so as to project upward from an outer circumference of the ceiling plate  40 . In the main body  10  which is integrally molded by blow molding of the resin, boundaries among the bottom plate  20 , the body portion  30 , and the ceiling plate  40  are not necessarily clear. Therefore, the “outer circumference of the bottom plate  20 ” can be considered as an “outer circumference of a lower end of the body portion  30 ”. Further, the “outer circumference of the ceiling plate  40 ” can be considered as an “outer circumference of an upper end of the body portion  30 ”. It is to be noted that the “lower annular portion  27 ” in the embodiment corresponds to an “annular portion” in the invention. 
     The recessed portion  50  includes the circular bottom surface  51  and the cylindrical inner circumferential surface  52 . The bottom surface  51  is provided at the center of the bottom plate  20 . The inner circumferential surface  52  is erected from an outer circumference of the bottom surface  51  and a diameter of the inner circumferential surface  52  is slightly increased to the upper side. The bottom surface  51  of the recessed portion  50  corresponds to a lowermost surface of the bottom plate  20 . Further, the above-described lower annular portion  27  is provided so as to project to a height lower than the bottom surface  51  of the recessed portion  50 . That is to say, in a state where a pressure in the main body  10  is not increased, the bottom surface  51  of the recessed portion  50  is located at a position higher than a grounding surface and the resin container  1  is grounded at a lower end surface of the lower annular portion  27 . 
     The bottom plate  20  includes an annular first bottom plate surface  21  along the outer circumference and a second bottom plate surface  22 . The second bottom plate surface  22  is slightly swelled inward from the first bottom plate surface  21  and reaches an upper edge of the recessed portion  50 . There arises the following advantage with a configuration in which the bottom plate  20  is slightly swelled from the outer circumference and reaches the recessed portion  50  as described above. That is, there arises an advantage that the lower end surface of the lower annular portion  27  can be set to a height lower than the bottom surface  51  of the recessed portion  50  even when the projecting length of the lower annular portion  27  is made shorter with the above-described configuration. That is to say, if the projecting length of the lower annular portion  27  is shorter, the lower annular portion  27  is easy to have a mechanical strength for supporting a weight of the entire resin container  1 . In addition, a shape of a mold is not complicated so that the blow molding is easily performed. 
     Heights of bottom surfaces of the groove portions  60  are substantially equal to that of the first bottom plate surface  21  and the groove portions  60  are formed in the radial direction of the bottom plate  20  so as to connect the first bottom plate surface  21  and the recessed portion  50 . In the embodiment, two groove portions  60  are formed. The two groove portions  60  are formed on the same line as a diameter of the bottom plate  20  while sandwiching the recessed portion  50  therebetween. Further, in the blow molding, a groove line having a V-shaped cross section of which both sides are slightly swelled, a so-called “parting line”, is formed along a bonding portion of a pair of split molds. The groove portions  60  in the embodiment are formed in the direction intersecting with a parting line  29 . 
     The outlet ports  45  are openings through which liquid is injected and discharged into/from the main body  10  and two outlet ports  45  are provided in the embodiment. The two outlet ports  45  are located on the same line as the diameter of the ceiling plate  40  so as to be separated from the center of the ceiling plate  40  by the same distance. Accordingly, the center of the recessed portion  50  (center of the bottom plate  20  in the embodiment) is not located on the virtual axis lines X extending from the centers of the outlet ports  45  in the container height direction. Each of the outlet ports  45  projects upward from the ceiling plate  40  in a cylindrical form and thread grooves are formed on the inner circumferential surface thereof. 
     The pipe  71  is attached to one of the two outlet ports  45  through a tap plug  75 . Threads are formed on an outer circumferential surface of the tap plug  75 . The threads are mounted on the thread grooves of the outlet port  45  so as to be fitted into the outlet port  45 . An upper end of the pipe  71  is connected to the tap plug  75  but the tap plug  75  is configured so as not to rotate the pipe  71  with the rotation of itself. Further, the tap plug  75  is configured so as to communicate an external pipe (not illustrated) and the pipe  71  in the main body  10  by connecting the external pipe to the tap plug  75  in a detachable manner. 
     The pipe  71  is made of a resin and has flexibility. The length of the pipe  71  is set such that the pipe  71  is curved in a state where the upper end of the pipe  71  is attached to the outlet port  45  through the tap plug  75  and the lower end thereof reaches the bottom surface  51  of the recessed portion  50 . Further, a tensile force acts on the pipe  71  having an extra length for the curved amount between the outlet port  45  and the recessed portion  50 . Therefore, the lower end of the pipe  71  is pressed against the opposite-side boundary portion  55 . 
     In the resin container  1  having the above-described configuration, the bottom surface  51  of the recessed portion  50  corresponds to the lowermost surface of the bottom plate  20 . Therefore, the liquid which has been reduced by being discharged through the pipe  71  flows into the recessed portion  50 . In the embodiment, the second bottom plate surface  22  higher than the first bottom plate surface  21  is present between the first bottom plate surface  21  and the recessed portion  50  on the bottom plate  20 . However, since the groove portions  60  connecting the first bottom plate surface  21  and the recessed portion  50  are formed, the liquid flows into the recessed portion  50  through the groove portions  60  without remaining on the first bottom plate surface  21 . 
     In addition, the parting line  29  which swells is present on the bottom plate  20 . Therefore, the reduced liquid cannot get across the parting line  29  and there arises a risk that the liquid is easy to remain at both sides of the parting line  29  on the first bottom plate surface  21 . However, in the embodiment, the groove portions  60  are formed in the direction intersecting with the parting line  29 . With this, the liquid flows into the recessed portion  50  through the groove portions  60  from both sides separated by the parting line  29  on the first bottom plate surface  21 . 
     Further, the lower end of the pipe  71  is located at the boundary between the bottom surface  51  and the inner circumferential surface  52  on the recessed portion  50 . Therefore, almost total amount of the liquid flown into the recessed portion  50  can be discharged through the pipe  71 . This makes it possible to discharge almost total amount of the liquid accommodated in the main body  10  through the pipe  71 . 
     Further, when the liquid is discharged with the pressure feeding system, the air is fed into the main body  10  from the outside. The air can be fed through the outlet port  45  to which the pipe  71  is not attached. Alternatively, when the tap plug  75  is configured to include a communicating path for feeding the air into the main body  10  from the outside in addition to the communicating path for discharging the liquid from the main body  10  to the outside through the pipe  71 , the outlet port  45  to which the pipe  71  is not attached may be sealed and the air may be fed into the main body  10  through the tap plug  75 . 
     If a pressure in the main body  10  is increased by feeding the air into the main body  10 , the ceiling plate  40  and the bottom plate  20  expand outward, as illustrated in  FIG. 2 . With this, the distance between the outlet port  45  and the bottom surface  51  of the recessed portion  50  is longer. In addition, if the ceiling plate  40  expands, the outlet port  45  and the tap plug  75  fitted thereinto are inclined and the vicinity of the upper end of the pipe  71  connected to the tap plug  75  is inclined. 
     However, the curved pipe  71  has the extra length. Therefore, even when the ceiling plate  40  and the bottom plate  20  expand, the tensile force keeps acting on the pipe  71  between the outlet port  45  and the recessed portion  50 . Therefore, the lower end of the pipe  71  stops at the opposite-side boundary portion  55  of the recessed portion  50  all the time. 
     A maximum height in the main body  10  (distance between the bottom surface  51  of the recessed portion  50  and the upper end of the outlet port  45  in the axial direction) is assumed to be L. Further, a distance between the center of the outlet port  45  and the opposite-side boundary portion  55  of the recessed portion  50  in the direction intersecting with the axial direction is assumed to be N. Under the assumption, the length of the pipe  71  is required to be longer than (L 2 +N 2 ) 1/2  in a state where the ceiling plate  40  and the bottom plate  20  do not expand. In addition, in this state, it is desirable that the length of the pipe  71  is equal to or shorter than (L+N). Further, if the length of the pipe  71  is set to be longer than the distance between the opposite-side boundary portion  55  and the outlet port  45  in a state where the ceiling plate  40  and the bottom plate  20  expand, the lower end of the pipe  71  can be located at the opposite-side boundary portion  55  of the recessed portion  50  even when the liquid is discharged with the pressure feeding system. In consideration of a result of examination of change of the distance between the opposite-side boundary portion  55  and the outlet port  45  between before and after the ceiling plate  40  and the bottom plate  20  expand in resin containers having various capacities, the length of the pipe  71  is preferably set to be in a range of 103% of (L 2 +N 2 ) 1/2  to (L+N). It is to be noted that since the size of the tap plug may be various, a length of the upper end of the outlet port to the lower end of the pipe is defined as the “length of pipe”. 
     Further, as a result of the examination, in order to stop the lower end of the pipe  71  at the opposite-side boundary portion  55 , it is effective that the length of the pipe  71  is set such that an entrance angle θ of the pipe  71  into the recessed portion  50  (angle formed by the vicinity of the lower end of the pipe  71  and the bottom surface  51  of the recessed portion  50 ) can be set to 35°±20°. It is considered that the above-described fact is based on balance between a component force in the direction toward the bottom surface  51  of the recessed portion  50  and a component force in the direction toward the inner circumferential surface  52  of the recessed portion  50  in the force acting on the lower end of the pipe  71  in a tensed state between the outlet port  45  and the recessed portion  50 . 
     As described above, with the resin container  1  according to the embodiment, almost total amount of the liquid flown into the recessed portion  50  can be discharged through the pipe  71  even with the pressure feeding system with which a large amount of liquid has been left in the conventional resin container. Eventually, almost total amount of the liquid accommodated in the main body  10  can be discharged through the pipe  71 . 
     Actually, when the liquid accommodated in the resin container having the capacity of 200 liters, which has the configuration in the embodiment, has been discharged with the pressure feeding system, the liquid which has not been discharged and has been left was equal to or less than 50 milliliters. The residual liquid is equal to or lower than one hundredth in comparison with 5 liters as the liquid residual amount when the liquid in the conventional resin container having the same capacity is discharged with the pressure feeding system, and is an extremely small amount. 
     As described above, the invention has been described by using a preferred embodiment. However, the invention is not limited to the above-described embodiment. Various improvements and changes in design can be made in a range without departing from a scope of the invention as will be described below. 
     For example, the two groove portions  60  are formed in the diameter direction of the bottom plate in the above-described embodiment. However, the invention is not limited thereto and much more groove portions can be provided around the recessed portion in a radial manner. Further, the groove portions may be formed such that the depths of the groove portions are gradually increased toward the recessed portion. 
     Further, the two outlet ports  45  are included in the above-described embodiment. However, the invention is not limited thereto and only one outlet port may be included. When one outlet port is included, the liquid can be also discharged with the pressure feeding system if the tap plug including the communicating path for feeding the air into the main body from the outside and the communicating path for discharging the liquid from the main body to the outside through the pipe is employed. 
     Further, the outlet port  45  to which the pipe  71  is attached is eccentric on the ceiling plate  40  and the recessed portion  50  is provided at the center of the bottom plate  20  in the above-described embodiment. However, the invention is not limited and it is sufficient that the center of the recessed portion is not located on the virtual axis line extending from the center of the outlet port in the container height direction. For example, a configuration in which the outlet port is eccentric on the ceiling plate and the recessed portion is eccentric in the opposite direction on the bottom plate can be employed. Alternatively, a configuration in which the outlet port is located at the center of the ceiling plate and the recessed portion is eccentric on the bottom plate can be employed. 
     In addition, the inner circumferential surface  52  of the recessed portion  50  has a cylindrical shape of which diameter is slightly increased toward the upper side in the above-described embodiment. However, the invention is not limited thereto and the inner circumferential surface  52  may have a vertical cylindrical shape of which diameter is the same as that of the outer circumferential circle of the bottom surface of the recessed portion. When the inner circumferential surface has the cylindrical shape of which diameter is increased toward the upper side, there is an advantage that moldability of the recessed portion is excellent. On the other hand, when the inner circumferential surface has the vertical cylindrical shape, there is an advantage that a stopper-like effect of holding a pressed tip of the pipe on the opposite-side boundary portion is enhanced. 
     In addition, the recessed portion  50  has a circular shape when seen from the above in the above-described embodiment. However, the shape of the recessed portion  50  is not particularly limited as long as the lower end of the pipe can be made to abut against the boundary between the bottom surface and the inner circumferential surface of the recessed portion  50 . For example, the recessed portion  50  may be a recessed portion including a bottom surface having an elliptical shape or a polygonal shape and an inner circumferential surface erected from the outer circumference of the bottom surface. It is to be noted that the recessed portion is formed by the blow molding of the resin as described above. Therefore, the expression “boundary between the bottom surface and the inner circumferential surface” of the recessed portion indicates a concept encompassing a case where a clear boundary line is not necessarily expressed.