GB2039980A - Improvements relating to bulk tanks - Google Patents

Abstract

Bulk tanks for holding fluent substances, such as liquids, powdered and granular solids, are constructed from reinforced plastics materials by a method which utilises prefabricated reinforced plastics shell components 10, 20, 30 etc., which are assembled together to provide a tank of the desired size and configuration and the assembled shells are themselves utilised as a mandrel onto which additional reinforced plastics is laid up directly to connect and unitise the shells. The invention also concerns the basic shell components each of which comprises a side wall 11 defining an internal cavity and an end wall 12 extending across the cavity and integral with the side wall at one end thereof, as well as the final tanks. <IMAGE>

Description

SPECIFICATION Improvements relating to bulk tanks This invention relates to bulk tanks for fluent substances, such as liquids, powdered and granular solids, and to methods for constructing such tanks, and in particular to tanks constructed from reinforced plastics.

It has been proposed to construct bulk tanks for fluent substances, including tanks for road transport vehicles, of reinforced plastics, by moulding, fabricating from preformed sheet or using curable liquid synthetic resins. Reinforced plastics possesses a number of advantages over metal, for example a reinforced plastics tank weighs less than an equivalent metal tank, which is advantageous for use on road vehicles, and reinforced plastics tanks are easier to repair when damaged than metal tanks.

The repair of metal tanks usually involves welding, and if the tank to be repaired has contained a liquid petroleum fuel then due to the presence of fuel vapour the necessary safety precautions which have to be taken before the actual work of repair can begin are expensive and time-consuming, and the carrying out of the work of welding itself can never be considered free from hazard. A reinforced plastics tank is not subjected to the above disadvantages, but hitherto the initial production cost of a reinforced plastics tanks has been substantially greater than that of an equivalent metal tank and this factor alone has actively discouraged the general adoption of reinforced plastics tanks.

The technique of producing tank shapes in using curable liquid synthetic resins has required the use of a rotatable mandrel to which layers of reinforcement material such as glass fibre, nylon, steel cords etc., and resin have been applied and allowed to cure before the shaped article can be stripped off.

The prior art has therefore made use of a rotatable mandrel which is the full size of the tank to be constructed. Reinforcement and resin has been laid up and wound helically on the mandrel and allowed to cure. In order then to extract the mandrel from the cured tank member, it has been necessary to cut through the entire tank wall longitudinally and strip the tank member from the mandrel.

In the case particularly of a bulk tank for a vehicle for transporting liquid fuels, it is necessary to provide bulkheads which sub-divide the interior of the tank into smaller compartments, both as a safety measure to act as baffles preventing surge of liquid fuel within the tank and also to provide separate compartments which can be filled as desired with fuels of different grades. After re-joining the tank side wall along the line of the cut made prior to removal from the mandrel, bulkheads which have been separately fabricated are installed in the tank which for this purpose is required to be open ended and thereafter separately fabricated outer end walls are bonded to the tank side wall.

The size and cost of the mandrel, together with the many production steps involved in the above method, has meant that it has been up to now relatively inconvenient and expensive to make bulk tanks in reinforced plastics as compared to metal.

It is an object of the present invention accordingly to simplify and rationalise the production method of bulk tanks in reinforced plastics.

Another object of the present invention is to provide methods of making reinforced plastics bulk tanks which are substantially less expensive to carry out.

Yet another object is to provide methods of making reinforced plastics bulk tanks which include the use of novel construction techniques.

A further object of the present invention is to provide reinforced plastics shell components which are capable of assembly with one or more other shell components to provide a bulktank of any desired size and configuration.

A still further object of the present invention is to provide reinforced plastics bulk tanks which include bulkheads and end walls as required integral with the tank side wall.

According to the invention a reinforced plastics bulk tank is constructed of two or more shell components each of which components comprises a side wall defining an internal cavity and an end wall extending across the cavity defined by the side wall and integral with the side wall at one end thereof.

Preferably the side wall is formed adjacent the end wall with a rebate which can be fitted into the open end of a second, shell, which open end has the same size and configuration as the rebate. In addition, it is preferred to provide a series of grooves in the side wall, and extending around the end wall, which grooves when two or more shells are assembled together end to end, extend the full length of the assembly of shells obtained and around the outer ends thereof and which can be filled with reinforced plastics to hold the assembly rigid for the application to the assembly of additional reinforced plastics.

The method according to the present invention includes the step of fabricating two or more modular shell components as above specified, assembling the shells end to end and laying additional reinforced plastics over and around the assembled shells to connect and unitise the shells.

A completed bulk tank may, for example, comprise four or more shells assembled and connected end to end in an arrangement which provides for first and second shells being placed with their open ends in conjunction, a third shell placed with its open end against the end wall of the second shell and a fourth shell placed with its open end against the end wall of the third shell. Such a tank will provide three compartments, one defined by the first and second shells and having a volume equal to the combined volume of the first and second shells, and second and third compartments each having a volume equal to the volumes of the third and fourth shells respectively. The end walls of the second and third shells constitute interior bulkheads in the tank which strengthen the tank, prevent dangerous surges of the contents and separate the individual compartments.

Any number of shells may be connected in any arrangement to provide a bulk tank having any desired overall shape, for example, parallel cylindric al, ovoid or parallelipided, or single or double taper or a combination of such shapes, and having any desired overall capacity and lay-out of compartments. The possibility also exists of providing an intermediate compartment between two adjacent shells which are arranged so that their end walls face each other but are spaced apart, and the shells are connected by means of a plain band of reinforced plastics which can effectively be considered as a continuation of the two side walls.

Itwill be appreciated that each individual shell component is of lesser size than the completed tank.

The individual shells, will normally be fabricated by laying up reinforcement and curable liquid synthetic resin on the exterior of a core or mandrel which the dimensions required for the interior of the shell and gives a smooth finish to the inner surface of the shell but no mandrel of the full size of the completed tank is required as the place of such mandrel for laying up the additional reinforced plastics which unitises the shells is taken by the shells themselves. Thus tooling costs are dramatically reduced in the present invention, with consequent substantial reduction in anticipated production costs. Further, the fact that tanks are constructed by modular techniques - the individual shells comprising the "modules" - can be expected to result in additional cost savings such as are well known to be attainable when such techniques are adopted.For example, the shells for parallel tanks can initially be fabricated all in standard sizes, any adjustment to suit any special requirement being made when they are placed together for the assembly of the complete bulk tank. Thus only one core is needed to produce shells which are capable of assembly to provide a wide variety of bulk tanks of different overall capacity and compartment lay-out, and this, as already stated, is relatively small and inexpensive.

The invention is further illustrated by way of example in the accompanying drawings whereof: Figure 1 is a perspective view of a typical parallel shell of the invention; Figure 2 is an elevation of the shell of Figure 1; Figure 2a shows a detail of a modification to Figure 2; Figure 3 is a side view of a completed tank for a road vehicle constructed in accordance with the invention; Figure 4 is an end view of the tank of Figure 3 and Figure 5 is a schematic exploded view of the component shells included in the make-up of the tank of Figures 3 and 4.

In the drawings, Figures 3 to 5 are shown to a reduced scale as compared with Figures 1 and 2.

Referring to Figures 1 and 2, a typical component shell 10 comprises a side wall 11 and an integral, domed end wall 12 at one end. Side wall 11 is stepped inwardly adjacent the end wall 12 to form a rebate 13 which can be fitted into the open end 14 of a second, similar shell.

The cross-section of shell 10 illustrated is ovoid, but the shell can, of course, be of any desired cross-sectional shape as previously stated. The side wall 11 is parallel to the longitudinal axis 15 of the shell as illustrated, but can be inclined thereto so that the shell is e.g. frusto-conical in configuration. A plurality of longitudinally extending grooves 16 are formed in the side wall 11 and across the end wall 12 for a purpose to be explained.

The shell 10 in this embodiment is fabricated by laying up reinforcement and a curable synthetic resin on the exterior of a core or mandrel (not shown) and is illustrated after curing and removal from the core. Removal is effected by sliding the shell off the mould in the direction of its longitudinal axis 15. The reinforcement may be any of those commonly known in the art, e.g. steel, nylon or polypropylene fibres, glass fibre, cloth or mat, or a combination of reinforcing materials.

Figure 2a shows a modification wherein a return member 12a is applied to the periphery of the end wall 12 and continues the line of the bottom of the rebate 13 to provide additional surface for bonding to other shells as described below, and has a smooth return face to avoid a re-entrant corner in the completed tank compartment which would be difficult to clean.

The shell 10 is a modular component whereof the side wall 11 and end wall 12 define and delimit an internal cavity or volume. The shell 10 is capable of assembly with other shells 20, 30,40 etc., to provide a bulktankfor liquids as will now be described with reference to Figures 3 to 5.

Figures 3 and 4 illustrate a bulk tank 100 for mounting on a road vehicle chassis (not shown). The tank 100 is assembled from modular shells as shown in Figures. A plurality of the shells 10,20.... 60 are assembled in adjacent axial alignment in the order shown and are brought into contacting relationship whereby rebate 23 of shell 20 enters open end 14 of shell 10 and is bonded to side wall 11. Rebate 33 of shell 30 enters the open end 24 of the shell 20 and is bonded to the side wall 21. Shell 40 is oriented so that its open end 44 is adjacent the open end 34 of shell 30. The side walls 41 and 41 are butt-jointed and secured by bonding and internal reinforcement (not shown) is added.The domed end walls 42 and 52 of the shells 40 and 50 are opposed to each other but are spaced apart and the shells are connected by means of a plain band 1101 of reinforced plastics having the same dimensional configuration as the side walls 41 and 51 and into which the rebates 43 and 53 are bonded. End shell 60 which consists essentially only of a short side wall 63 and domed end wall 62 is butt-jointed and bonded to the open end 54 of shell 50. Band 1101 may comprise a side wall portion cut from a shell 60 which was fabricated originally to a greater length. The domed end walls 12 and 62 of the endmost shells can be strengthened by bonding onto each of them a reinforcing cap 70 which covers the end wall.

The grooves 16 in the side walls of the shells 10....

60 and preferably also the band 1101 extend longitu dinallythefull length of the assembly and around the end walls 12 and 62 ofthe end shells 10 and 60.

These grooves are filled with a reinforcement, suitably a carbon fibre reinforcement, and resin which strengthens the basic structure of tank 100 obtained by disposing and connecting the shells 10 to 60 and 1101 as just described.

Such basic structure is then used as a "mandrel" for the application of additional reinforcement and resin. This additional reinforcement is laid up on the basic structure and wound helically, transversely or longitudinally around the shells and resins applied to connect and unitise the shells and develop the ultimate strength required of the tank wall. In this connection, the end walls 12 to 62 may be fabricated originally with their ultimate required strength.

However, they and the side walls 11 to 51 and band 1101 can be fabricated originally with less than ultimate strength, for example approximately half their ultimate required strength, as the remainder of the ultimate strength required can be supplied by the additional reinforcement and resin. The reinforced plastics in the grooves 16 serves to hold the structure rigid while it is turned while performing its function as a "mandrel" for the winding of the additional reinforcement until the desired thickness is obtained.

In the final completed tank 100, Figures 3 and 4, the end walls 12 and 62 (with reinforcement caps 70 when provided) of the shells 10 and 60 constitute the tank outer end walls and the end walls 22,32,42 and 52 define partitions inside the tank which strengthen the tank and sub-divide the tank internally to provide compartments 101,102,103, 104 and 105. Itwill be seen that the capacities of the individual compartments differ according to the lengths of the side walls 11 etc., and the orientation of adjoining shells, so that any desired arrangement and capacity of compartments can readily be produced.

As shown the tank 100 is then finished by bonding thereto a prefabricated reinforced plastics cat-walk 120. For mounting the tank 100 to a transport vehicle, prefabricated reinforced plastics chassis 121 with saddles are bonded to the tank 100. The chassis 121 is mounted on a steel sub-chassis 122 for connection to the transport vehicle, for example a road vehicle which includes a prime mover, a trailer or a semi-trailer, or a railway vehicle.

The invention is, of course, applicable to static bulk tanks as well as to tanks for road vehicles.

Shells for tapered tanks may be constructed and the tank completed as described. Parallel shells and taper shells may be combined. It is, of course, necessary that the shells have the same size and shape where they are required to mate one with another. A disparity can, of course, be overcome by using an adapter band similar to band 1101.

Claims (16)

1. A method of constructing a bulk tank for holding a fluent substance, comprising fabricating at least two shell components of reinforced plastics construction each of which components comprises a side wall defining an internal cavity and an end wall extending across the cavity defined by the side wall and integral with the side wall at one end thereof, assembling the shells end to end in longitudinally aligned relationship and laying additional reinforced plastics over and around the assembled shells to connect and unitize the shells.

2. A method according to Claim 1, wherein each shell component is fabricated on a mandrel having the dimensions required for the interior of the shell component and said component is removed from the mandrel after curing.

3. A method according to Claim 1 or Claim 2, wherein each shell component is fabricated to include one or more grooves in the external surface thereof which grooves extend longitudinally of the side wall and around the end wall, said groove or grooves in adjacent shells assembled end to end extending longitudinally the full length of the assembly and around the end wall of the endmost shells, and wherein said groove or grooves are filled with reinforced plastics to hold the assembly rigid prior to the laying of the additional reinforced plastics over and around the assembled shells.

4. A method according to any one of Claims 1 to 3 further comprising reinforcing the end walls of the endmost shells of the assembly by bonding onto each said end wall a reinforcing cap which covers said end wall.

5. A reinforced plastics shell component for use in the method according to any one of Claims 1 to 4, which comprises a side wall defining an internal cavity and an end wall extending across the cavity defined by the side wall and integral with the side wall at one end thereof.

6. A reinforced plastics shell component according to Claim 5 which includes one or more grooves in the external surface thereof which grooves extend longitudinally of the side wall and around the end wall.

7. A reinforced plastics shell component according to Claim 5 or 6, wherein the sidewall is stepped inwardly adjacent the end wall to form a rebate adapted to fit into the open end of a second, similar shell.

8. A reinforced plastics shell component according to any one of Claims 5 to 7 which includes a return member attached to the periphery of the outer face of the end wall to continue the line of the side wall or the rebate across the end wall.

9. A bulk tank for holding a fluent substance which comprises two or more prefabricated shell components of reinforced plastics construction each of which components comprises a side wall defining an internal cavity and an end wall extending across the cavity defined by the side wall and integral with the side wall at one end thereof, said shells being bonded end to end in longitudinally aligned relationship, and additional reinforced plastics applied over and around the shells to connect and unitize the shells and increase the wall thickness to a predetermined thickness.

10. A bulk tank according to Claim 9 which includes reinforcing fibres which extend longitudinally of and across the ends of the bonded shells.

11. A bulk tank according to Claim 9 or 10 which includes two said shell components bonded together with their open ends in conjunction.

12. A bulk tank according to Claim 9 or 10 which includes two adjacent shells arranged so that their end walls face each other but are spaced apart, and a reinforced plastics band having the same configuration as the side wall interposed between and bonded to said spaced apart shells to define an intermediate compartment.

13. A bulk tank according to any one of Claims 9 to 12 wherein the outer end walls include a bonded reinforcement cap.

14. A method of constructing a bulktankfor holding a fluent substance, substantially as hereinbefore described with reference to the accompanying drawings.

15. A reinforced plastics shell component for use in constructing a bulk tank, substantially as hereinbefore described with reference to the accompanying drawings.

16. Abulktankforholding afluentsubstance substantially as hereinbefore described with reference to the accompanying drawings.