Abstract:
The present disclosure relates to an apparatus ( 10 ) for pressurizing a first substance, such as a liquid, gas or particulate material, to a pressure substantially equal or similar to the pressure of a second substance, i.e. a reference substance. The pressure of the reference substance may be transient so the pressure of the first substance must be varied accordingly. The present disclosure includes a bladder ( 71 ) disposed within a sealed can ( 40 ), an inlet passage ( 24   a ) in communication with the interior ( 41 ) of the can and an outlet passage ( 26   a ) in communication with the interior of bladder ( 71 ). The reference substance may be directed into the interior ( 41 ) of the can ( 40 ) via the inlet passage ( 24   a ) and pressurizes the bladder ( 71 ) and thus the first substance stored therein, thereby causing the first substance to be expelled via the outlet passage ( 26   a ) with a pressure substantially corresponding to that of the reference substance. Many applications exist that require two substances to be of a similar pressure. For example, an engine may be adapted to run on low lubricity fuel provided a pressurized lubricant is introduced to the pressurized fuel before being directed towards the injector.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a device for pressurizing a substance and more particularly to a device for pressurizing a substance to a pressure substantially equal or similar to that of another substance. The present disclosure also relates to component parts for such a device. 
       BACKGROUND 
       [0002]    Some installations use or consume various substances, including gases, liquids or particulates. Furthermore, those installations may require some of those substances to be at a particular pressure, and sometimes at a pressure substantially equal or similar to that of another substance. This requirement may be for various reasons, including the possibility of subsequently combining controlled quantities of first and second substances to create a composition of specific proportions of each substance. The effective control of those quantities may be improved when the first and second substances are at substantially the same pressure. The first and second substances may comprise particulates, liquids or gases and the composition may comprise a combination of any of those, e.g. a mixture of particulates and liquids. 
         [0003]    Furthermore, the pressure of the first substance may be transient and therefore it may be necessary to be able to vary the pressure of the second substance accordingly. That is to say, it may not be appropriate merely to compress the second substance to a set pressure because the first substance may not be at a constant pressure. The pressure of the second substance must be adjusted rapidly in response to a sudden change in the pressure of the first substance. 
         [0004]    Some installations requiring two substances of equal or similar pressures may be large, fixed installations where space and energy are of little concern. However, some smaller, mobile installations exist where available space and energy for pressurizing the second substance are rather limited and thus a significant concern. 
         [0005]    For example, the engine of a vehicle uses or consumes various substances, such as fuels, coolants, refrigerants, lubricants, emissions fluids, hydraulic fluids and many other substances that may be pressurized or even combined with other substances. For instance, those engines may be adapted to run on alternative fuels that may need to be mixed with a lubricant prior to consumption to prevent excessive friction between moving parts, such as fuel pumps. 
         [0006]    Systems are known for combining two or more substances, such as fuel and lubricant. However, those systems store the fuel-lubricant mixture in the tank ready for consumption and the substances are known to separate when left for some time or as they are drawn from the tank. This leads to fuel-lubricant mixtures having inconsistent quantities of fuel and lubricant. 
         [0007]    Although the present disclosure is particularly relevant to industrial installations such as engines and heavy machinery, it is believed to be equally as applicable to any other apparatus requiring two or more substances to be of substantially equal or similar pressures. 
         [0008]    It is an object of the present disclosure to address the problems associated with known pressurization systems so as to provide a pressurization system and a pressurization method with more versatility. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    According to a first aspect of the disclosure, there is provided an additive container for connection to a pressurization device having a fluid inlet passage for receiving pressurized fluid and an additive outlet passage for dispensing pressurized additive, the additive container comprising: a flexible bladder for holding additive and having a bladder outlet through which additive may be expelled; and a support member provided on the flexible bladder and defining pressurization device connection means adapted to support the additive container relative to the pressurization device and to arrange the bladder outlet in fluid communication with the additive outlet passage. 
         [0010]    According to a further aspect of the present disclosure, there is provided a pressurization device comprising: a first housing part defining a fluid inlet passage and an additive outlet passage; a second housing part detachably mounted to the first housing part, which together define a chamber in fluid communication with the fluid inlet passage; an additive container disposed within the chamber and defining an additive flow passage arranged in fluid communication with the additive outlet passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    One embodiment of the present disclosure will now be described in detail, with reference being made to-the accompanying drawings, in which: 
           [0012]      FIG. 1  is a front perspective view of pressurization device according to the disclosure; 
           [0013]      FIG. 2  is an exploded view of the pressurization device of  FIG. 1 ; 
           [0014]      FIG. 3  is a front perspective view corresponding to  FIG. 1 , but with the can of the device removed for clarity. 
           [0015]      FIG. 4  is a top perspective view of a head unit forming part of the pressurization device of  FIGS. 1 to 3 ; 
           [0016]      FIG. 5  is a bottom perspective view of the head unit of  FIG. 4 ; 
           [0017]      FIG. 6  is a cross-sectional view along the lines A-A shown in  FIG. 4 ; 
           [0018]      FIG. 7  is a cross-sectional view along the line B-B shown in  FIG. 4 ; 
           [0019]      FIG. 8  is a perspective view of the additive container forming part of the pressurization device of  FIGS. 1 to 3 ; 
           [0020]      FIG. 9  is an alternative perspective view of the additive container with the bladder removed for clarity, thus presenting a support member; 
           [0021]      FIG. 10  is a cross-sectional view through the centre of the additive container shown in  FIG. 8 ; 
           [0022]      FIG. 11  shows a second alternative support member for the additive container; 
           [0023]      FIG. 12  shows the second alternative support member in a different configuration; 
           [0024]      FIG. 13  shows a third alternative support member for the additive container; 
           [0025]      FIG. 14  shows the third alternative support member in a different configuration; and 
           [0026]      FIG. 15  shows a cross-section through the centre of the device of  FIG. 1 , the device being fitted with an additive container furnished with the third alternative support member. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The following is a detailed description of an exemplary embodiment of the present disclosure. The exemplary embodiment described therein and illustrated in the drawings is intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiment is not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims. 
         [0028]    Referring to  FIGS. 1 to 3 , there is shown a device, generally indicated  10 , for pressurizing a substance (not shown). The device  10  may be used for pressurizing a first substance contained in the device  10  to a pressure corresponding substantially to that of another substance. The device  10  is configured to pressurize a liquid substance, though it may also be suited to gaseous substances or particulate substances. In particular, the device  10  may be arranged for use with an additive such as a lubricant to be introduced to a fluid such as a liquid fuel, and thus serves to pressurize the additive to a pressure corresponding to that of the fluid. Controlled amounts of additive may be more easily introduced to the fluid when the additive and fluid are at the same pressure. 
         [0029]    The device  10  may comprise a first housing part  11  to which the fluid may be delivered and from which the additives may be expelled at substantially the same pressure as the fluid. A second housing part  40  may be connected to the first housing part  11 , which together define an interior space  41 . An additive container  70  may be disposed within that interior space  41  and secured to the first housing part  11 , the second housing part  40  or both to maintain its position. Each of which will be described in more detail below. 
         [0030]    The first housing part  11  may fulfill several functions, such as providing a means of closing the interior of the second housing part  40 , a means of directing additives (not shown) away from the device  10  and also a means of directing fluid towards the device. It may also provide a means of mounting the device  10  to a larger assembly, such, as an engine. 
         [0031]    Referring now also to  FIGS. 4 to 7 , the first housing part  11  is generally cup-shaped insofar as it may define part of the interior space  41 . Furthermore, the first housing part  11  may include an upper portion  12  that may be domed and a lower portion  13  that may be substantially cylindrical. 
         [0032]    The upper portion  12  may define a substantially concave inner surface  14  and a convex outer surface  15 . The interior space  41  includes an annular wall  16  depending substantially from the centre of the concave inner surface  14  so as to define an inner chamber  17  and an outer chamber  18 . In this example the annular wall  16  is generally circular such that the inner chamber  17  is generally cylindrical and the outer chamber  18  is generally toroidal, though the annular wall  16  may be polygonal or any other shape. 
         [0033]    The upper portion  12  may include fluid ports  20 , 21  for the delivery and expulsion of fluid and additive ports  22 , 23  for the expulsion of additives from the device  10 . For example, the fluid ports  20 , 21  for the supply and expulsion of fluid may be located so as to communicate with the outer chamber  18  and the additive port  22  for the expulsion of additives may be located so as to communicate with the inner chamber  17 . There may be any number of ports arranged in various positions on the upper portion  12  so as to provide a choice of configurations according to the space available within the installation. 
         [0034]    Furthermore, the convex outer surface  15  may be furnished with fluid port members  24 , 25  and additive port members  26 , 27 . Each fluid port member  24 , 25  and additive port member  26 , 27  may define a passage  24 A, 25 A, 26 A, 27 A having an inner end defined by a respective fluid port  20 , 21  or additive port  22 , 23  and an outer end defined by an opening  24 B, 25 B, 26 B, 27 B formed in an end face  24 C, 25 C, 26 C, 27 C. Specifically, the fluid port members  24  and  25  may be arranged such that their fluid passages  24 A, 25 A intersect the outer chamber  18  and the additive port members  26 , 27  are arranged such that their passages  26 A, 27 A intersect the inner chamber  17 . Further, fluid port members  24 , 25  and additive port members  26 , 27  may be arranged to extend outwardly from the periphery of the upper portion  12  and the end faces  24 C, 25 C, 26 C, 27 C may be suitably arranged to receive a connector (not shown) provided on the end of a hose, pipe or suitable conduit (not shown). For instance, the end faces  24 C, 25 C, 26 C, 27 C may be substantially flat and may be orientated in parallel planes. In the exemplified embodiment, the openings  24 B, 25 B, 26 B, 27 B in each end face may be threaded so as to receive a threaded end portion of the connector provided on the end of a hose, pipe or suitable conduit. Each connector may have a flange adjacent the threaded portion that may bear against the end face  24 C, 25 C, 26 C, 27 C of the fluid port members  24 , 25  and additive port members  26 , 27  when fully tightened. The flange may be hexagonal or otherwise suitably profiled to enable the connector to be fully tightened by hand or an appropriate tool. 
         [0035]    One additive port  23  is plugged in the present example since it is not required for this particular installation. Were that additive port  23  to be required, it may be unplugged simply by drilling through the passage  27 A such that the passage communicates with the inner chamber  17 . In the present embodiment the fluid port members  24 , 25  and the additive port members  26 , 27  are arranged generally parallel to one another. Furthermore, the fluid port members  24 , 25  may be arranged such that their fluid passages  24 A, 25 A are joined, and are possibly coaxial to aid flow. One of the openings  24 B, 25 B may be arranged as an inlet and the other as an outlet. In this way, when the fluid passages  24 A, 25 A are joined, some fluid may flow directly between the inlet and the outlet, while some fluid may flow in and out of the interior space  41 , via the ports  20 , 21 . 
         [0036]    An annular lip  30  may be defined within the first housing part  11  and which may delineate the upper and lower portions  12 , 13 . In the present embodiment, the annular lip  30  extends outwardly from a circumferential edge of the upper portion  12  and provides an interior surface against which the additive container  70  may bear when the device  10  is properly assembled. The lower portion  13  may comprise a skirt  32  depending downwardly from the outer circumferential edge  33  of the annular lip  30  so as to enclose a portion of the interior space  41 . In this instance, the upper and lower portions  12 , 13  are both the same shape, though this need not necessarily be so. For instance, they may take different shapes depending on the size and shape of the installation or the size and shape of the additive container  40 . The skirt  32  may be furnished with a threaded portion  34 , possibly on its internal surface for engagement with a threaded portion  45  provided on the second housing part  40 . 
         [0037]    The first housing part  11  may be provided with a mounting bracket  35  by which the device  10  may be mounted to the installation (not shown), for example, an engine. The mounting bracket  35  may extend upwardly from an exterior surface of the annular lip  30  and may be arranged in a plane substantially normal to the plane of the annular lip  30 , though other orientations may be preferable, again depending on the installation. Furthermore, a web  36  may extend between the mounting bracket and the upper portion  12  to provide increased rigidity. The mounting bracket  35  may be provided with one or more holes  37  for receiving bolts (not shown) or other suitable fasteners for securing the device  10  to the installation. 
         [0038]    Referring again to  FIGS. 1 to 3 , the second housing part  40  may be a receptacle provided with an opening  42  adapted to connect to the first housing part  11  and sized to accommodate part of the additive container  70 . The opening  42  may be adapted to engage sealingly with the first housing part  11  so as to avoid the egress of fluid flowing between those parts. In the present embodiment, the second housing part  40  is generally cylindrical with a rim  43  defining the opening  42  and the other end  44  being closed, though the second housing part  40  may take many shapes according to the available space within the installation. The second housing part  40  may include a threaded portion  45  for engagement with the threaded portion  34  of the skirt  32  of the first housing part  11 . Since the threaded portion  34  is provided on the interior of the skirt  32 , the threaded portion  45  in the present example is provided on the exterior of the second housing part  40 . The depth of the threaded portion  45  of the second housing part  40  may be selected so that the rim  43  of the second housing part  40  may locate against or near the interior surface of the annular lip  30 . Furthermore, the second housing part  40  may be furnished with an outwardly extending annular flange (not shown) disposed adjacent the threaded portion  45  and distal from the rim  43  so as to define a surface against which the free edge of the skirt  32  may bear when the second housing part  40  is connected to the first housing part  11 . In addition, the second housing part  40  may be provided with a seal (not shown), such as an O-ring or the like, that may be lodged between the annular flange and the skirt  32  to restrict the egress of fluid therebetween. 
         [0039]    In an alternative embodiment (not shown), the opening of the second housing part  40  and the skirt  32  of the first housing part  11  may be arranged to form a snug fit and may be secured by bolts or other suitable fasteners. 
         [0040]    The can may be made of plastics or other material impermeable to the fluid for which the additive device may be used. 
         [0041]    With reference to  FIGS. 3 and 8  to  10 , the additive container  70  may comprise a bladder  71  and a support member  80 . The bladder  71  may comprise a main body  72  having a neck  73  defining an opening  74  into the interior  75  of the main body  72 . The bladder  71  may be made from a material which is impermeable to the fluid and the additives with which the device  10  is to be used and which may enable the bladder  71  to deform elastically when subject to external pressure. 
         [0042]    The support member  80  may be connected to the bladder  71  and may locate securely within the first housing part  11 . The support member  80  may include a collar  81  over which the neck  73  of the bladder  71  locates and which may take any shape, though in the present example it is substantially circular. The neck  73  of the bladder  71  may be clamped onto the collar  81  by a ferule  82  or other mechanism that may create a hermetic seal between the collar  81  and the bladder  71 . The collar  81  may include a flow passage  84 , which may take any shape, but in the present embodiment is cylindrical since it is defined by the inner circumferential face of the collar. The support member  80  may further include support means  85  which may extend outwardly from the collar  81  for supporting the additive container  70  on the second housing part  40  or the first housing part  11 . In one embodiment (not shown), the support means  85  may include a plurality of struts extending from the collar  81 , possibly in a radial direction, and having free ends that locate against the interior surface of the annular lip  30 . 
         [0043]    In the present embodiment the support means  85  include a disc having opposed upper and lower faces  87 , 88  and an aperture  89  extending between those upper and lower faces  87 , 88 . The collar  81  may depend downwardly from the lower face  88  and the aperture  89  may be sized and positioned such that its axis is coaxial with that of the collar  81 . This way, the collar  81  and the aperture  89  may together define the flow passage  84  for additives being expelled from the bladder  71 . 
         [0044]    The outer periphery  90  of the disc  85  may have a substantially uniform thickness and may locate on the interior surface of the annular lip  30  so as to be trapped in position by the rim  43  of the second housing part  40  once it is screwed onto the skirt  32 . In the present example, the outer periphery  90  of the disc  85  carries an annular seal  91  ( FIG. 10 ) to restrict the leakage of fluid between the second housing part  40  and the first housing part  11 . The annular seal  91  may be of a flexible nature such that as it is compressed between the annular lip  30  and the rim  43  of the second housing part  40  it may extend laterally towards the skirt  32  to prevent the egress of fluid from the device  10 . 
         [0045]    Orifices  95  may be defined within the disc  85 , possibly at a location proximal to the outer periphery  90  of the disc or adjacent the annular seal  91  if present, thereby enabling fluid in the outer chamber  18  to pass beyond the support member  80  and into the interior space  41  of the second housing part  40 . To facilitate this, the upper face  87  of the disc may be frusto-conical so as to cause fluid falling thereon to drain towards the orifices  95 . 
         [0046]    A portion of the aperture  89  adjacent the upper face  87  of the disc  85  may be diametrically larger than the remainder of the flow passage  84  so as to define an annular recess  97 . The annular recess  97  may be furnished with an annular seal  98 , which may be adhered or otherwise secured within the annular recess. The annular seal  98  may have an internal diameter which is larger than the internal diameter of the flow passage  84  such that part of the annular recess  97  remains visible when the annular seal  98  is in place. Thus, when the device  10  is fully assembled, the free end of the annular wall  16  depending from the concave inner surface  14  of the first housing part  11  may locate in and form a snug fit with the annular seal  98 . The inner diameter of the annular wall  16  may be at least as large as the diameter of the flow passage  84  so as not to restrict flow. 
         [0047]    To prevent additives leaking from the additive container  70  prior to assembly, the flow passage  84  may be temporarily closed by a removable cap or bung (not shown). For instance the cap may sit within the annular recess  97  and may be removed and disposed of immediately before fitting the additive container  70  to the device  10 . 
         [0048]    Two alternative types of support members  80 ′, 80 ″ are shown in  FIGS. 11 to 15 , which include a closing mechanism that opens automatically during installation. Each of these will be discuss separately below. 
         [0049]    Referring to  FIGS. 11 and 12 , the support member  80 ′ is provided with a closing member  100 , which is disposed within the flow passage  84  and arranged for sliding movement therealong between closed ( FIG. 11 ) and open ( FIG. 12 ) positions. The closing member  100  may be generally cylindrical and may be sized to form a snug fit within the flow passage  84 . Thus, the cross-section of the closing member  100  may correspond to the shape of the flow passage  84 . The closing member  100  may be tubular and may have one closed end  101  and one open end  102 , the closed end in this particular embodiment being the end proximal to the bladder  71 . The closing member  100  may also include one or more inlets  103  formed adjacent the one closed end  101  and optionally one or more outlets  104  formed towards the one open end  102  so as to facilitate flow of additives from the bladder  71  to the inner chamber  17 , when the closing member  100  is in its open position, as shown in  FIG. 12 . 
         [0050]    Furthermore, the closing member  100  may be provided with abutments  106 , 107  at the closed and open ends  101 , 102 , respectively. The abutment  106  at the closed end may extend at least part way around the closing member  100  so at to engage the free end of the collar  81  when in its closed position. This serves to limit axial displacement of the closing member  100  in a direction away from the bladder  71  and also to serve as a seal. The sealing characteristics may be further improved by the provision of an O-ring  108 , or equivalent seal, adjacent the abutment  106  at the closed end for engaging the annular wall  16 . 
         [0051]    The abutment  107  at the open end may serve to limit axial displacement of the closing member  100  into the bladder  71  while permitting insertion of the closing member into the flow passage  84 . The abutment  107  at the open end may be angled relative to the collar  81  so as to define a sloping surface  110  and an abutment surface  111 . The sloping surface  110  may cause the closing member  100  to deflect or deform slightly as it is urged into the flow passage  84  during assembly and the abutment surface  111  may engage the annular recess  97  should attempts be made to remove the closing member  100  from the flow passage  84 . 
         [0052]    The support member  80 ″ shown in  FIGS. 13 to 15  may include a closing member  120  which may also be adapted to slide along the flow passage  84 . In the present example, the closing member  120  is generally cylindrical and has abutments  121 , 122  at opposed ends  123 , 124  much like those of the first arrangement described above. However, this second closing member  120  need not be tubular, but may include elongate recesses  126  extending partway along its length so as to define a flow path for the fluid. The elongate recesses  126  may be longer than the length of the flow passage  84 , but extend between the interior  73  of the bladder  71  and the inner chamber  17  of the head unit only when the second closing member  120  is in its open position ( FIG. 14 ). In the closed position, the ends of the elongate recesses  126  are within the flow passage  84  so cannot be accessed from the interior  73  of the bladder  71 , thus restricting the flow of additive towards the inner chamber  17 . 
       INDUSTRIAL APPLICABILITY 
       [0053]    To fit the device  10 , first of all the first housing part  11  may be attached to the installation. This may be achieved by presenting the mounting bracket  35  to an appropriate surface on the installation such that the holes  37  align with corresponding holes formed in the appropriate surface. The first housing part  11  may be secured in place by bolts extending through the holes  37  and the corresponding holes in the appropriate surface. 
         [0054]    The second housing part  40  and the additive container  70  may then be connected to the first housing part  11 . The easiest way to do this may be first to position the additive container  70  on the second housing part  40  such that the bladder  71  locates within the interior space  41  and the outer periphery  90  rests on the rim  43  of the second housing part  40  defining the opening  42 . The second housing part  40  and the additives container  70  may then be secured to the first housing part  11 . This may be achieved by screwing the second housing part  40  onto the skirt  32  so as to engage the threaded portion  45  with the threaded portion  34 . Once the second housing part  40  is fully screwed onto the first housing part  11 , the outer periphery  90  of the support member  80  will be firmly clamped between the annular lip  30  of the first housing part  11  and the rim  43  of the second housing part  40 . The clamping pressure may cause the annular seal  91  to deform so as to extend radially and thus seal the interface between the first housing part  11  and the second housing part  40 . Furthermore, the annular wall  16  depending from the concave inner surface  14  may locate in the annular recess  97  and against the annular seal  98  so as to restrict or prevent additives leaking into the outer chamber  18 . 
         [0055]    The modified additive containers shown in  FIGS. 11 to 15  include a second closing member  100 , 120  that is activated automatically as the second housing part  40  is screwed onto the first housing part  11 . The closing member  100  shown in  FIGS. 11 and 12  engages one or more abutments  110  extending radially inwardly from the annular wall  16 , thereby preventing axial movement of the closing member  100  relative to the first housing part  11  as the second housing part  40  and the support member  80  advance further into the first housing part  11 . The relative axial movement of the closing member  100  and the support member  80 ′ effectively leads to the closing member  100  lowering into the bladder  71  and opening the flow passage  84 . 
         [0056]    The closing member  120  shown in  FIGS. 13 to 15  works in a very similar manner to the closing member  100  of  FIGS. 11 and 12 . The main difference is that the end of the second closing member  120  proximal to the first housing part  11  may engage a stud  130  depending from the concave inner surface  14 . This stud  130  prevents axial movement of the second closing member  120  relative to the first housing part  11 , as the second housing part  40  and the support member  80  advance towards the first housing part  11  during the screwing action. 
         [0057]    It is then a case of plumbing the device by attaching the connectors (not shown) of the conduits to the corresponding openings  24 B, 25 B, 26 B, 27 B of the fluid port members  24 , 25  and the additive port members  26 , 27  and also by plugging any superfluous openings. The connector provided on the end of the additive delivery hose may be threaded on to the opening  26 B of the additive port member  26  such that the flange of the connector bears against the end face  26 C. Depending on the configuration of the installation and thus the available space, it may be preferable to attach the additive delivery hose to the additive port member  27 , which might require the passage  27 A to be drilled and the passage  26 A to be plugged. Similarly, the connector provided on the end of the fluid delivery hose may be threaded into the opening  25 B of the fluid port member  25  and the connector provided on the end of the fluid supply hose may be threaded onto the opening  24 B of the fluid port member  24 . Since the fluid passages  24 A, 25 A in the fluid port members  24 , 25  each lead to the outer chamber  18 , they may be conversely configured depending on the hose routing of the particular installation. That is to say, the connector of the fluid delivery hose may be attached to the opening  24 B of the fluid port member  24  and the connector of the fluid supply hose may be attached to the opening  25 B of the other fluid port member  25 . 
         [0058]    In use, fluid may flow through the fluid supply hose, through the passage  24 A of the fluid inlet port member  24  and into the outer chamber  18  whence it flows through the orifices  95  and into the interior space  41 . Fluid may be drawn from the interior space  41 , outer chamber  18  and passage  25 A of the fluid port member  25  and delivered through the delivery hose to another components, such as a mixer. Fluid may also flow directly between the fluid passages  24 A, 25 A. 
         [0059]    The pressure of the fluid in the interior space  41  is substantially the same as the pressure of the fluid elsewhere in the system. The fluid in the interior space pressurizes the bladder  71 , which in turn pressurizes the additives inside the bladder  71 . Those additives are then expelled through the flow passage  84 , through the passage  26 A within the additive port member  26  and through the additive delivery hose whereat the pressure of the additives is substantially equal to the pressure of the fluid in the system. The additives may then flow towards another component, such as the mixer where they may be introduced to the fluid.