Patent Publication Number: US-8985135-B2

Title: System for dosing fluid

Description:
FIELD OF DISCLOSURE 
     The present disclosure relates to blocks containing an active substance which dissolve into or are eroded by a flow of fluid and to systems and apparatuses for enabling their use. 
     BACKGROUND 
     Systems have been previously proposed which provide in-line mixing of a substance such as a fire retardant foaming agent or a fertiliser for example with water by flowing the water past a block containing the substance such that block dissolves or erodes to dose the water with the substance. 
     One of the problems with any such system is being able to control the rate of dosing of the substance in the water as it flows past the block, so that a generally constant composition of the mixture or solution is provided. 
     SUMMARY OF THE DISCLOSURE 
     According to one aspect of the disclosure there is provided a system for dosing a stream of fluid with at least one active substance, the system comprising: 
     a housing which defines a chamber having an inlet and an outlet to enable the flow of fluid through the chamber; and 
     a block containing the active substance, the block comprising a body having an outer surface and a passage therethrough defining an inner surface, and wherein the block is positioned within the housing chamber in an operative position between the inlet and the outlet so that in use fluid flows over the inner and outer surfaces of the block to dissolve and/or erode the block. 
     According to a further aspect of the disclosure, there is provided a block for dosing a stream of fluid with at least one active substance, the block containing the active substance and comprising a body having an outer surface and a passage therethrough defining an inner surface, and wherein the block is configured to be used so that fluid flows over the inner and outer surfaces of the block to dissolve and/or erode the block. 
     Throughout the specification, the term “active substance” is intended to mean any substance that is to be added to the stream of fluid to achieve a function within the fluid and/or by the application of the stream of fluid. For example, the active substance may be a surfactant for fire fighting applications, a detergent for cleaning applications, a fertiliser, pesticide, insecticide or herbicide for agricultural or gardening applications, a foam stabiliser or a corrosion inhibitor. 
     The block has a first end and a second end and the inner and outer surfaces preferably extend longitudinally between the first and second ends. 
     The block may have a first face at its first end and a second face at its second end and the inner and outer surfaces may be generally perpendicular to the first and second faces. 
     The passage of the block may extend longitudinally between the block&#39;s first and second ends, preferably opening in the first and second faces. 
     The block may be of approximately constant thickness between its inner and outer surfaces along the length of the block. 
     The block may comprise a carrier material through which the at least one active substance is distributed. 
     The carrier material may be soluble in water. 
     The carrier material may be polyethylene glycol having an average molecular weight of 1000-8000 MW. 
     The block may be positioned in its operative position within the chamber such that its inner and outer surfaces are generally parallel to the direction of flow of fluid between the inlet and outlet of the chamber. 
     The block may be positioned in its operative position within the chamber such that its first face faces the inlet of the chamber and its second face faces the outlet of the chamber. 
     The system may also comprise a holding assembly for holding the block in its operative position within the chamber between the inlet and the outlet. 
     The holding assembly may comprise a first plate and a second plate and wherein the block is held between the plates in its operative position. 
     The chamber has an inner side surface(s) and each plate has a peripheral edge which may be configured to abut the inner side surface(s) of the chamber. 
     The first face of the block may butt against a surface of the first plate and the second face of the block may abut against a surface of the second plate when the block is in its operative position. 
     The holding assembly may comprise at least one fastener for fastening the block to minimise lateral movement relative to the first and second plates. 
     The at least one fastener may comprise one or more spikes projecting from a surface from the first and/or second plates which engage the block in its operative position. 
     Each spike may engage a portion of the block which is approximately equally spaced between its inner and outer surfaces. 
     Each plate may have a plurality of spikes projecting from a surface and which are arranged in a circular array. 
     Each plate may have apertures to enable the passage of fluid past the plates. 
     The holding assembly may also comprise one or more positioning members for positioning the block in its operative position within the chamber. 
     The positioning member(s) may position the block relative to the first and/or second plates. 
     The positioning member(s) may comprise at least two rods extending longitudinally within the chamber. 
     In its operative position, the inner surface of the block may abut the rods. However, in another form the outer surface of the block abuts the rods. 
     The rods may project from a surface of the second plate and the first plate may have apertures to enable the plate to fit over the rods. 
     The holding assembly may also comprise a first spacing arrangement for spacing the holding assembly away from the chamber inlet and may also comprise a second spacing arrangement for spacing the holding assembly away from the chamber outlet. 
     The chamber may have a first end wall in which the inlet is located and the first spacing arrangement may comprise at least one spacing member that extends between the first plate and the first end wall. 
     The chamber may have a second end wall in which the outlet is located and the second spacing arrangement may comprise at least one spacing member that extends between the second plate and the second end wall. 
     Each spacing member may comprise a portion of one of the positioning members. 
     In another embodiment, each spacing member may comprise the head of a pin that is inserted through the respective plate and into the block. In this embodiment, the pins act also as the fasteners for fastening the block to minimise lateral movement relative to the first and second plates. 
     The system may also comprise a fluid flow distributor to distribute the fluid entering the chamber through the chamber&#39;s inlet to flow over the inner and outer surfaces of the block. 
     The fluid flow distributor may comprise a plate having an inner set of apertures for directing fluid to flow over the inner surface of the block and an outer set of apertures for directing fluid to flow over the outer surface of the block. 
     The flow distributor plate has a peripheral edge which may abut the inner side surface(s) of the chamber. 
     The inner set of apertures may be arranged in a circular array and the outer set of apertures may be arranged in a circular array. 
     In one particular form, the flow distributor plate is the first plate of the holding assembly. 
     The ratio of the total cross-sectional area of the inner set of apertures to the total cross-sectional area of the outer set of apertures may be generally equal to the ratio of the surface area of the inner surface of the block to the surface area of the outer surface of the block. Without wishing to be bound by theory, it is understood that having these generally equal ratios enables the increase in the dissolution/erosion rate of the inner surface of the block (as its surface area increases) to be generally equal to the decrease in the dissolution/erosion rate of the outer surface of the block (as its surface area decreases), for a constant flow rate of fluid through the chamber. 
     The sum of the cross-sectional area of the inner and outer sets of apertures may be generally equal to the cross-sectional area of the inlet to the chamber. 
     According to a further aspect of the disclosure, there is provided a block for dosing a stream of fluid of the system having any one or more features of the block described above. 
     According to another aspect of the disclosure there is provided an apparatus for use in dosing a stream of fluid with at least one active substance from a block containing the active substance, the apparatus comprising: 
     a housing which defines a chamber having an inlet and an outlet to enable fluid to flow through the chamber; and 
     a holding assembly for holding the block in an operative position within the chamber between the inlet and the outlet. 
     The housing and the holding assembly of the apparatus may have any one or more of the features described above in respect of the system. 
     According to a further aspect of the disclosure, there is provided a block for dosing a stream of fluid with at least one active substance and for use with the apparatus having any one or more of the features of the apparatus described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described, with reference to the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a system for dosing a stream of fluid with at least one active substance according to an embodiment; 
         FIGS. 2-6  are perspective views of the system of  FIG. 1  at various stages of assembly; 
         FIG. 7  is a cut-away view of the system of  FIG. 1  during use; 
         FIG. 8  is an exploded perspective view of a system for dosing a stream of fluid with at least one active substance according another embodiment; 
         FIGS. 9 and 10  are perspective views of the system of  FIG. 8  at various stages of assembly; 
         FIG. 11  is a cut-away view of the system of  FIG. 8  during use; and 
         FIG. 12  is a perspective view of an assembled system for dosing a stream of fluid with at least one active substance according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring to  FIGS. 1-7 , a system  10  for dosing a stream of fluid with at least one active substance according to an embodiment the disclosure herein is shown. The system  10  comprises a housing  11  which defines a chamber  12  having an inlet  13  and an outlet  14  to enable fluid to flow through the chamber. Inside the chamber  12  is located a solid block  15  containing the active substance(s). The system  10  also comprises a holding assembly  16  to hold the block  15  in an operative position within the chamber  12  during use of the system. 
     The block  15  is an annular or hollow cylinder in shape, although it may be of any other suitable shape such as a square or rectangular prism based shape. The block  15  thus has a passage  24  extending through the body of the block and defining an inner surface  20  having an inner surface area. The body of the block also defines an outer surface  21  having an outer surface area. The block also has first and second ends  22 ,  23 . The inner and outer surfaces  20 , 21  extend longitudinally between the first and second ends such that the passage  24  defined by the block opens in a first face  25  of the block at its first end  22  and a second face  26  of the block at its second end  23 . The inner and outer surfaces  20 , 21  are generally perpendicular to both of the first and second faces  25 ,  26 . The passage  24  is also centrally located in the block such that the longitudinal axis of the passage  24  is co-axial with the longitudinal axis of the block  15 . Thus, the block  15  is of approximately constant thickness between inner and outer surfaces  20 ,  21  along the length of the block between its first and second ends  22 ,  23 . Although the block may be of other dimensions, in one form the block has a height of 50 mm, an outer diameter of 90 mm and an inner diameter of 40 mm. Such a block has been found to be suitable for dosing 1000 litres of water. 
     The composition of the block  15  is dependent on the application for which it is to be used. The active substance(s) in the block  15  may consist of surfactants for fire fighting applications, detergents for cleaning applications or fertilisers, pesticides, insecticides or herbicides for agricultural or gardening applications or any other one or more active ingredients as desired. The one or more active substances may also comprise a foam stabiliser(s) and may also comprise a corrosion inhibitor(s). 
     In any of these applications, the block  15  also consists of a solid carrier for carrying the active substance(s). The active substance(s) are evenly distributed throughout the solid carrier matrix. A suitable solid carrier is polyethylene glycol having an average molecular weight of between 1000 and 8000 MW. However, any other suitable substance may be employed as the solid carrier, which is preferably water soluble. 
     Although the block may be of other dimensions, in one form the block has a height of 50 mm, an outer diameter of 90 mm and an inner diameter of 40 mm. Such a block (formed of polyethylene glycol) has been found to be suitable for dosing 1000 litres of water. 
     The holding assembly  16  comprises first and second plates  30 ,  31  between which the block  15  is sandwiched (see  FIG. 4 ). Each plate  30 ,  31  has inner and outer surfaces with the inner surfaces  32 ,  33  of the plates facing each other. The block  15  is held such that the first face  25  of the block abuts and is flush against the inner surface  32  of the first plate  30  and the second face  26  of the block abuts and is flush against the inner surface  33  of the second plate  31 . This acts against fluid flowing over the first and second faces in use, which is important in maintaining a generally constant rate of dosing of the active substance into the fluid as it flows through the chamber. Each plate  30 ,  31  is a generally circular disc and they are configured such that the centre of each plate is axially aligned with central longitudinal axis of the block passage  24  when the block  15  is assembled with the holding assembly  16 . 
     The holding assembly  16  also comprises fastener(s) in the form of spikes  35  on the inner surfaces  32 ,  33  of the plates  30 ,  31  which engage the block  15  and minimise lateral movement of the block relative to the plates including after the block has been used and is partially dissolved. The spikes  35  dig into the block at the block&#39;s first and second ends respectively when the block is assembled with the holding assembly. The spikes  35  are arranged in a circular array and are positioned on the inner surfaces of the plates such that they each engage a portion of the block which is generally equally spaced between its inner and outer surfaces  20 , 21  when the block  15  is assembled with the holding assembly  16 . 
     Although these fasteners are shown in the form of spikes  35  in the  FIGS. 1-7 , other arrangements could be used such as for example a ridge or a plurality of ridge portions. In this embodiment, the block  15  may have a groove or groove portions formed in each of its first and second faces for receiving the ridge or ridge portions when assembled with the holding assembly. 
     The holding assembly  16  also comprises positioning members in the form of three rods  36  projecting from the inner surface  33  of the second plate  31 . The rods  36  are equidistantly spaced from the centre of the second plate  31  and are arranged so that the passage  24  of the block  15  can fit over all of the rods  36  with the inner surface  21  of the block  15  butting against each of the rods  36 . In this way, the rods  36  accurately position the block  15  with respect to the second plate  31  when they are assembled prior to use. 
     The rods  36  are of greater length than the length of the block  15  and the first plate  30  of the holding assembly  16  is also provided with apertures  37 , one for each of the rods  36  to extend through at their distal ends from the second plate  31 . This enables the first plate  30  to be accurately positioned with respect to both the second plate  31  and the block  15 . The apertures  37  are equidistantly spaced from the centre of the first disc  30  in a circular array. The distal ends of the rods may be threaded so that nuts can be applied to tighten and fasten the block between the plates. 
     Although in the embodiment shown in  FIGS. 1-7 , the holding assembly  16  has three rods, more or less rods may be incorporated into the assembly. In other embodiments, different forms of positioning members may be used to accurately position the block with respect to the second plate such as spigots, a ridge or ridge portions. In one form, each of the first and second plates has separate positioning members for positioning each plate with respect to the block. For example, each plate may have spigots, provided on their respective inner surface and spaced equidistantly around the centre of that plate, which are received in the passage of the block and abutting the block&#39;s inner surface when the plates are assembled with the block. 
     The first plate  30 , which when the system  10  is assembled is located proximate to the inlet  13  of the chamber  12 , also acts a fluid flow distributor to distribute the fluid after it enters the chamber  12  through its inlet  13  to flow past the inner and outer surfaces  20 ,  21  of the block. To achieve this, the first plate  30  comprises inner and outer sets of apertures  40 ,  41 . The outer set of apertures  41  are provided in a circular array around the periphery of the first plate  30 , so that fluid which passes through the outer set of apertures flows past the outer surface  21  of the block  15 . The inner set of apertures  40  provided in a circular array (that is generally parallel to the outer array) towards the centre of the first plate  30 , so that fluid which passes through the inner set of apertures flows past the inner surface  20  of the block  15 . In the embodiment shown in  FIGS. 1-7 , the apertures  37  through which the rods  36  extend to position the first plate  30  with respect to the second plate  31  are located within the array of this inner set of apertures  40 . 
     In the embodiment shown in  FIGS. 1-7  the apertures in the inner set  40  are of generally the same size and shape as the apertures in the outer set  41  and that there are more apertures in the outer set than in the inner set. However, the apertures in each set may be of any shape or number provided that during operation, for a constant flow rate of fluid through the chamber  12 , the increase in the dissolution/erosion rate of the inner surface of the block (as its surface area increases) is generally equal to the decrease in the dissolution/erosion rate of the outer surface of the block (as its surface area decreases). This is achieved, at least in part, by designing the inner and outer sets of apertures  40 ,  41  such that the ratio of the total cross-sectional area of the inner set to the total cross-sectional area of the outer set is generally equal to the ratio of the surface area of the inner surface  20  of the block to the surface area of the outer surface  21  of the block. The aperture design should also be such that there is an even flow of fluid across the inner and outer surfaces of the block respectively, hence why in the embodiment shown in  FIGS. 1-7  the inner and outer sets of apertures  40 ,  41  are organised in circular arrays. These design features ensure that the rate of dosing of the active substance to the fluid as it passes through the chamber  12  remains generally constant for a constant fluid flow rate over the life time of the block  15  even though the surface area of the inner surface increases as it dissolves and/or erodes and the surface area of the outer surface decreases as it dissolves and/or erodes. Towards the end of the life of the block, it has been found that a thin tubular ring of the block material remains centred on the spikes  35 . 
     The inner and outer sets of apertures  40 ,  41  are also designed so that the sum of the cross-sectional area of the inner and outer sets is generally equal to the cross-sectional area of the inlet  13  to the chamber  12 . This is to minimise the pressure drop across the chamber  12 . 
     The second plate  31 , which when the system  10  is assembled is located proximate to the outlet  14  of the chamber  12 , may also have a inner and outer sets of apertures  42 ,  43  as shown in  FIGS. 1-7 . The apertures in the second plate  31  are generally in alignment with the apertures in the first plate  30 . However, in other embodiments, broader inner and outer openings may be provided in the second plate  31  in place of the sets of apertures. 
     Although in the embodiment shown in  FIGS. 1-7  and described above the first plate of the holding assembly acts as a flow distributor of the fluid to the inner and outer surfaces of the block, in other embodiments, the first plate may have wide inner and outer openings to allow the free passage of fluid and a separate flow distributor may be incorporated with the system. 
     The housing  11  is cylindrical in shape in conformity with the cylindrical shape of the block  15  and the circular shape of the plates  30 ,  31 . However, the housing may be of other suitable shapes generally depending on the shape of the plates and the block. The housing comprises a base  50 , a wall  51  (or walls) integrally formed with the base and a removable cap  52  which couples to the wall  51  at its distal end from the base  50  to define and enclose the chamber  12 . The distal end of the wall  51  and the cap  52  are provided with screw threads to enable this engagement. An O-ring (not shown) or other suitable arrangement is provided to seal the closure by the cap  52 . The outlet  14  from the chamber  12  is formed centrally in the base  50  and the inlet  13  to the chamber  12  is formed centrally in the cap  52 . The wall  51  is shaped so that the peripheral edges of the first and second plates  30 ,  31  of the holding assembly  16  butt against the inner surface of the wall  51 . The block  15  is held by the holding assembly  16  within the chamber  12  so that its inner and outer surfaces  20 ,  21  are generally parallel to the inner surface of the housing wall  51  and also generally parallel to the direction of fluid flow from the inlet  13  to the outlet  14  of the chamber  12 . 
     The holding assembly  16  and the block  15  sit within the chamber  12  defined by the housing  11  such that there is head space  55  above the holding assembly at the inlet end of the of chamber. This is to enable proper distribution of the fluid by the fluid flow distributor in the form of the apertures  40 ,  41  in the first plate  30  to the inner and outer surfaces  20 ,  21  of the block respectively. A bottom space  56  is also provided at the outlet end of the chamber below the holding assembly and the block to allow fluid passing across the inner and outer surfaces of the block to exit the same outlet from the chamber. The bottom space  56  is created by legs  57  projecting from the outer surface  58  of the second plate  31  (which may be extensions of the rods  36 ) which sit on the base  50  of the housing. In another arrangement, the bottom space is created by a lip provided on the inner surface of the wall  51  of the housing above the base  50  on which the second plate  31  sits. 
       FIGS. 8-11  show a system  110  for dosing a stream of fluid with at least one active substance according to another embodiment of the disclosure which is similar to the system  10  of  FIGS. 1-7 . 
     The main difference for the system  110  of  FIGS. 8-11  is that the holding assembly  116  comprises a plurality of pins  170  associated with the first and second plates  130 ,  131  respectively. The pins  170  are inserted through respective plates such that their spike portions  171  extend towards the opposite plate. The head  172  of each pin  170  extends away from the plate in which the pin has been inserted in the opposed direction to its spike portion  171 . 
     The pins  170  provide two functions. Firstly, their spike portions  171  act as the fasteners to minimise lateral movement relative to the first and second plates. As a result, the spikes  35  provided on the plates in the system shown in  FIGS. 1-7  are unnecessary. The heads  172  of the pins also provide spacing arrangements at either end of the holding assembly  116  in which they space the holding assembly and in particular the first and second plates  130 ,  131  away from the chamber inlet  113  and outlet  114  respectively by butting against the housing cap  152  and base  150  respectively. This minimises movement of the holding assembly  116  longitudinally within the chamber so as to avoid the plates  130 ,  131  getting too close to either the chamber&#39;s inlet or the outlet which would undesirably constrict or block fluid flow through the chamber. 
       FIG. 12  shows an assembled system which could be either of the systems  10 ,  110  shown in  FIGS. 1-11 . The system  10 , 110  is provided with fittings to enable use of the system. These fittings include brackets  280  for mounting the system for example to a vehicle such as a ute, tractor or firetruck. In addition an inlet fitting  281  for coupling to a liquid supply conduit such as a fire hose and an outlet fitting  282  for coupling to a liquid outlet conduit are also provided. It is to be appreciated that types of fittings shown in  FIG. 12  are only representative and that other suitable fittings may be provided. 
     In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 
     It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention.