Roto-molded tank with improved performance for road transport

Abstract

The present invention relates to a tank (10) with a capacity of at least 1 m³, intended to contain a liquid load and designed for road transport. The tank is obtained by a rotational molding process using a rotating mold. The tank extends along a longitudinal axis (X) over a total length (LXT) from a front end (E1) to a rear end (E2). The tank comprises at least one first cross-sectional restriction zone at a first longitudinal position (PL1) along the longitudinal axis. According to the invention, the tank includes a wave-breaking insert (2) mounted within the tank. The first cross-sectional restriction zone forms a first longitudinal passage with a reduced cross-section at which the wave-breaking insert is placed, thus providing hydraulic damping to limit the displacement of the liquid in the event of sudden braking. Abstract figure: Fig. 3

Description

Title of the invention: Rotomolded tank with improved performance for road transport

[0001] The present invention relates to tanks, cisterns, or reservoirs suitable for containing liquids, for example, water. Furthermore, this discussion focuses on tanks, cisterns, or reservoirs intended for transport by road. More specifically, these tanks, cisterns, or reservoirs can be mounted on one or more axles, in which case they are referred to as 'water tankers'.

[0002] This type of water tank can usually be hitched to an agricultural tractor and used as a trailer.

[0003] Alternatively, these tanks, cisterns or reservoirs can be mounted on a rolling platform such as, for example, a multi-purpose flatbed trailer or on a flatbed truck.

[0004] For the sake of brevity, in the following we will use the term 'tank' to refer to tanks, cisterns or reservoirs as described above.

[0005] It is known that when a tank is moving with a vehicle at a certain speed, and the vehicle brakes quite heavily, a forward movement of the fluid inside the tank occurs due to inertial forces. This phenomenon adversely affects braking efficiency and can be surprising for the vehicle's driver. This phenomenon is all the more dangerous when the trajectory is curved, e.g., in the case of braking in a curve.

[0006] We are essentially interested here in the phenomenon along the longitudinal axis of displacement when braking is applied.

[0007] This phenomenon also exists in the opposite direction when the vehicle accelerates, but its effects are less problematic.

[0008] The phenomenon described above is all the more problematic during braking when the tank is filled between 50% and 75% of its volumetric capacity.

[0009] The tanks of interest here are of fairly large capacity, typically at least 1 m³ volumetric capacity. In practice, a tank of the agricultural water tank type can have a volumetric capacity between 3 m³ and 10 m³

[0010] For such volumes, the most suitable manufacturing process is a rotational molding process. The tank of interest here is therefore obtained by a rotational molding process.

[0011] The rotational molding technique is unique; it allows for the formation of large-volume hollow plastic parts but does not allow for the creation of every desired shape within that volume. Consequently, it is difficult to envision internal shapes that promote hydraulic damping directly from the molding process using rotational molding.

[0012] The inventors sought to propose a tank obtained on the one hand by the roto-molding technique and on the other hand which has high hydraulic damping capacities to mitigate the effects of powerful braking when the tank is filled between half and 2 / 3.

[0013] For this purpose, a tank with a capacity of at least 1m3 is proposed, intended to contain a load of liquid, and intended to be transported by road, said tank being obtained by a rotomolding process, said tank extending, along a longitudinal axis over a total length, from a front end to a rear end, the tank comprising at least a first section restriction zone, at a first longitudinal position along the longitudinal axis, characterized in that the tank includes a wave-breaking insert mounted in the tank, the first section restriction zone forming a first longitudinal passage with a reduced section at the location of which the wave-breaking insert is placed.

[0014] Advantageously, the presence of the wave-breaking insert provides hydraulic damping during braking suffered by the moving tank, the longitudinal forward movement of the liquid being reduced and / or delayed.

[0015] This limits the undesirable effects that can disrupt the vehicle's braking.

[0016] It should be noted that the "wave-breaking" insert can also be called a "blade-breaking" insert in practice. In Anglo-Saxon terminology, the term "anti-sloshing insert" is used.

[0017] We will see later that the insert can take several forms and can be an overmolded insert or an insert placed in the tank after molding.

[0018] The wave break insert can be a full-perforated partition or a partial partition. It There may be several partitions.

[0019] As will be discussed later, the wave break insert can be overmolded or insertable after molding.

[0020] The wave break insert can be formed in the same material as the tank body.

[0021] It is noted that the wave-breaking insert is not necessarily in the same position longitudinal than the first longitudinal passage with reduced cross-section; however, the wave-breaking insert is located in the vicinity of the first longitudinal passage with reduced cross-section, in the flow of liquid which passes longitudinally through the longitudinal passage with reduced cross-section.

[0022] Furthermore, the roto-molding process seeks to manufacture a hollow body with the most homogeneous material thickness possible to ensure wall continuity everywhere without thickness imbalance or significant local excess of material (a significant local excess of material would lead to excessive material consumption and / or a higher than desired weight of the manufactured object).

[0023] According to one embodiment, the material thickness of the roto-molded tank is between 3 mm and 12 mm, preferably between 4 mm and 8 mm. A target material thickness of between 5 and 6 mm can be aimed for.

[0024] According to one embodiment, the wave-breaking insert is located in a longitudinal position corresponding to the first longitudinal position.

[0025] It is noted that the wave break insert is located in the middle of the first section restriction zone.

[0026] We then advantageously have an optimal synergistic contribution of the wave-breaking insert to the hydraulic damping during braking.

[0027] According to one embodiment, the first longitudinal position is located at a first distance DI from the front end, DI being between 15% and 50% of the total length LXT, preferably between 20% and 35% of the total length LXT.

[0028] In practice, the first longitudinal position can preferably be chosen closer to the front of the tank, for example in the vicinity of the first quarter of the length.

[0029] According to one embodiment, the overall dimensions are such that the length LXT is greater than the height HT and the width WT. For large volumetric capacities, one can choose: LXT > 2 x HT and LXT > 2 x WT.

[0030] According to one embodiment, the tank may further include a manhole, preferably on its upper part, which can be closed by a cover.

[0031] The manhole can be round in cross-section. The diameter of the manhole can be between 40 and 50 cm.

[0032] This hole allows access for an operator into the internal volume of the tank, for example to clean the internal walls of the tank, the bottom of the tank, the drain filter or for any other task.

[0033] As will be seen later, the cover can be independent of the wave-breaking insert, or alternatively the cover can be connected to the wave-breaking insert.

[0034] According to one embodiment, the wave breaker insert is mounted removably in the tank.

[0035] In this configuration, there is no need to place the wave-breaking insert in the mold before pouring and mold rotation. The rotomolding operation thus remains simple and highly repeatable.

[0036] Furthermore, if the wave break insert is not made of the same material as the tank body, then for recycling, the wave break insert can be removed and thus separated from the tank in separate plastic material recycling circuits, in particular polyethylene and other recyclable polymers.

[0037] According to one embodiment, the wave break insert is wedged in the lower part via a system of complementary shapes.

[0038] Thus, there is no need for special fixing, it is sufficient to provide at least one shape in the bottom of the tank and a complementary shape in the bottom of the wave-breaking insert to provide an immobilization function in X and Y. Immobilization in Z is done from the top of the insert.

[0039] According to one embodiment, the manhole cover covers the wave break insert and is connected to the wave break insert.

[0040] This forms a compact and ingenious solution, the cover serving on the one hand to close the manhole and on the other hand to fix the wave-breaking insert at the top.

[0041] It is not excluded to use a solution where the cover and the wave-breaking insert are a single piece, the cover then being held in place via an auxiliary screwing or clipping system.

[0042] According to a particular embodiment, the lid can itself be screwed relative to the tank body.

[0043] According to one embodiment, the wave-breaking insert is overmolded, the wave-breaking insert being placed in the rotary mold before the plastic material is poured. In this configuration, the tank is directly equipped with the wave-breaking insert. Note that there may be one or more wave-breaking inserts arranged along the longitudinal axis of the tank.

[0044] According to one embodiment, the insert has a general ladder shape. A ladder-like structure provides rigidity and robustness.

[0045] According to one embodiment, longitudinal reinforcement bars are provided in the upper part on the sides of the tank, the reinforcement bars being arranged outside the internal volume of the tank.

[0046] According to one embodiment, the wave-breaking insert can be perforated. For example, the wave-breaking insert can include a multitude of through holes. This provides improved hydraulic damping when the fluid has to pass through the wave-breaking insert.

[0047] According to an alternative embodiment, the wave-breaking insert is solid. As a result, the wave-breaking insert is very simple and inexpensive.

[0048] According to one embodiment, a second section restriction is provided at a second longitudinal position and a second wave-breaking insert, the first position and the second position being symmetrical with respect to a median transverse plane of the tank.

[0049] The behavior is then identical in both directions of movement.

[0050] This solution proves relevant when the tank can be placed on a tray without taking care of the front or rear part.

[0051] According to one embodiment, a restriction ratio SR / ST is defined as the ratio between the reduced section SR and the envelope section ST, the reduced section corresponding to the passage section of the longitudinal passage with reduced section, reduced by the obstruction opposite by the wave break insert, the restriction rate being between 3% and 50%, preferably between 4% and 33%, and even more preferably between 5% and 15%.

[0052] According to one embodiment, three regularly spaced and distributed section restriction zones are provided along the longitudinal axis.

[0053] This allows for a pleasing aesthetic for the tank, viewed from the outside. Each of the section restriction zones can contribute to the hydraulic damping effect. However, it is also possible that one or even two of the section restrictions may have only a moderate hydraulic damping effect, with or without a wave-breaking insert.

[0054] According to one embodiment, the rotomolding material is polyethylene. Optionally, a proportion of the polyethylene comes from polyethylene recycling streams. Furthermore, the use of a plastic such as polyethylene avoids potential corrosion problems found in tanks made of steel.

[0055] According to one embodiment, the equipped tank is equipped with a supporting chassis and at least one axle, which then forms a rolling assembled tank.

[0056] The invention is particularly applicable to tanks with a volumetric capacity > 4 m3.

[0057] The invention will be further detailed by describing non-implementation embodiments limiting, and based on the attached figures illustrating variants of the invention, in which: - [Fig.1] schematically illustrates a top view of a tank according to a general example conforming to the present invention; - [Fig.2] schematically illustrates a horizontal section of the tank according to the example of [Fig.1]; - [Fig.3] schematically shows in perspective a section along a plane vertical, offset from the median plane, of an example according to a first embodiment with a removable wave-breaking insert; - [Fig.4] schematically shows an elevational view of the tank according to a example of implementation; - [Fig. 5] shows a cross-section of the tank according to the first method of realization, illustrating the reduced passage section providing hydraulic damping as desired; - [Fig. 6] illustrates the lower part of an example of a wave break insert and its interface with the bottom of the tank; - [Fig.7] illustrates in perspective view an example of a wave break insert removable; - [Fig-8] shows a perspective view of the lower portion of the tank body according to the first embodiment; - [Fig.9] shows a diametrical cross-sectional view of the upper portion of the wave break insert and the cover that covers it; - [Fig. 10] shows a perspective cross-sectional view of the upper portion of the wave break insert and the cover that covers it; - [Fig. 11] is analogous to [Fig. 2] and shows a variant of the first mode of realization ; - [Fig. 12] schematically shows another example according to a second method of embodiment with an overmolded wave-breaking insert; - [Fig. 13] shows an example of a perforated partition with holes, which can be used in the example according to the second embodiment; - [Fig. 14] schematically shows a water tank including a reservoir in accordance with the present invention.

[0058] In the various figures, the same reference numerals designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale. In particular, the thickness of the tank wall may have been exaggerated to facilitate understanding of the figures.

[0059] Here we use an orthogonal spatial frame such that the Z direction is vertical, the X direction corresponds to a longitudinal direction, which will generally be the direction of the longest dimension of the tank and the Y direction corresponds to a so-called 'transverse' or 'lateral' direction, perpendicular to the X direction. The orthogonal spatial frame in question is generally visible in the figures.

[0060] The tanks of interest here are suitable for containing liquids and have a large capacity, typically at least 1 m³ of volumetric capacity. In practice, a tank of the type considered may have a volumetric capacity between 3 m³ and 10 m³.

[0061] Depending on the various possible applications, the tanks of interest here may contain liquids such as water or aqueous compositions, or liquids such as liquid fuels like hydrocarbon or alcohol-based fuels, preferably biofuels. The tank material is chosen to be chemically compatible and inert with respect to the fuel.

[0062] The tanks of interest in this document are obtained by a rotational molding process. This process has been used for about forty years to manufacture hollow bodies made of plastic. Examples include US3822980 and US4102624, which describe machines and associated processes relating to rotational molding.

[0063] The rotomolding technique makes it possible to form large volume hollow plastic parts with a relatively homogeneous wall thickness.

[0064] The material thickness E0 of the roto-molded tank is generally between 3 mm and 12 mm.

[0065] The material thickness will preferably be between 4 mm and 8 mm. For the tanks of interest here, a target material thickness of between 5 and 6 mm can be aimed for.

[0066] Figure 1 shows an example of a tank 10 in top view. The tank extends along the longitudinal axis X from a front end E1 to a rear end E2. The cross-section at the X axis, visible in particular in Figure 5, is generally rounded, not necessarily circular. In particular, a lower support face is provided to ensure the stability of the tank when it is placed on a trailer platform or on the ground.

[0067] The tank length is denoted LXT, the width WT, and the height HT. The width WT is constrained by the maximum road clearance; typically, WT will be chosen to be between 2 m and 2.40 m. The height HT is of the same order of magnitude. Due to centrifugal force in curves, it is preferable to avoid an excessively high height HT. Therefore, it is the last dimension, namely the length LXT, that will be adjusted to determine the volumetric capacity of the tank to be constructed.

[0068] For large volumetric capacities, i.e. greater than 4 m3, LXT > 2 x HT and LXT > 2 x WT can be chosen.

[0069] The front end is slightly convex. The rear end is slightly convex. The cross-section is not constant, as will be seen in detail later. According to one embodiment, the cross-section of the tank is ovoid, with a wide flat bottom for stable placement and curved sides. The top may be convex or flat.

[0070] The first figures show the tank alone, which can, for example, be carried on a flatbed trailer. However, as illustrated in [Fig. 14], showing a water tank configuration, the tank can be mounted on a chassis 90 with a drawbar 91 and at least one axle 92, so that it can be towed by an agricultural tractor or another type of vehicle.

[0071] The tank is equipped with a drain valve 61 and includes filling ports 93, 94.

[0072] The tank may have fixing points on its lower part to serve as a base for attaching to a platform or rolling chassis. The tank may be clamped or strapped to a platform or rolling chassis, as a unit in itself and therefore not described in detail here.

[0073] The constituent material of the rotomolded tank is polyethylene. Of course, one can choose to form the tank with primary polyethylene, but it is necessary Note that it is also possible to use a primary polyethylene composition in combination with a proportion of polyethylene from recycling circuits that are now well established for this material.

[0074] It should be noted that the use of polyethylene avoids any corrosion phenomenon encountered with conventional steel tanks which necessarily have weld joints which are particularly prone to the appearance of rust or corrosion which causes leaks in the long term.

[0075] It is also noted that a plastic tank is lighter than a steel tank for the same given capacity.

[0076] It is noted that it is not excluded to use other synthetic materials, for example based on another plastic polymer.

[0077] Furthermore, the synthetic plastic material can be loaded with reinforcing fibers, e.g. glass fibers, carbon fibers or any other type of reinforcing fiber.

[0078] As is conventional for a tank or reservoir, the tank is equipped with a drain plug and a drain valve, located at a drain connection at the lowest point of the tank. Furthermore, the tank includes one or more filling ports, located on the top of the tank.

[0079] We are now interested in the dynamic behavior of such a tank filled with liquid. The liquid in question may be water or another aqueous-based liquid, for example milk, a plant protection product, or a liquid fertilizer. The liquid in question may also be a fuel.

[0080] Modern agricultural tractors can travel on the road network at a speed of up to 50 km / h, including when towing a trailer, for example in our case of interest a water tanker.

[0081] Special features are provided to improve the behavior of the coupling (tractor + trailer) in the case of braking from a fairly high speed, for example from 45 km / h.

[0082] For this purpose, a hydraulic damping function is provided to reduce the effect of the movement of the liquid inside the tank.

[0083] The tank includes at least one first section restriction zone, at a first longitudinal position PLI along the longitudinal axis X. The first section restriction zone ZI forms a first longitudinal passage with a reduced section, compared to the passage section in the current section, that is to say in the portions of the tank which do not contain a section restriction.

[0084] In addition, the tank includes a wave breaker insert 2 mounted in the tank.

[0085] The wave break insert is generally arranged at the location of the first section restriction zone.

[0086] In all the embodiments presented, by virtue of the characteristics which can be obtained by the rotomolding process, the wave break insert 2 is a separate part from the tank body, the tank body being obtained directly from the rotomolding process, i.e. the solidification of the liquid plastic material which has been introduced into the cavity in the mold.

[0087] According to a first embodiment illustrated in figures 1 to 11, the wave-breaking insert 2 is a separate part mounted removably in the tank.

[0088] According to another embodiment described later, the wave-breaking insert 7 is a part overmolded inside the tank, and in this case it is not removable.

[0089] In the example illustrated in Figures 1 to 10, the wave-breaking insert 2 is located at a longitudinal position PLA corresponding to the first longitudinal position PLI. The position correspondence can be strict, meaning that the wave-breaking insert is located exactly in the middle of the section restriction zone.

[0090] However, we see from [Fig. 11] that a suitable hydraulic damping result can also be obtained with a longitudinal position of the wave break insert slightly forward or slightly backward relative to the first longitudinal position PLI where the section restriction zone is located.

[0091] As can be seen in Figures 2 and 12, the first longitudinal position PLI is located at a first distance Dl from the front end. Generally, DI is between 15% and 50% of the total length LXT.

[0092] In a particular example, DI is preferably between 20% and 35% of the total length LXT. Simulation tests of fluid displacement under severe braking were conducted, and it turns out that this range of positions (from 20% to 35% of LXT) for the section restriction zone and the wave-breaking insert is particularly effective for tank fillings between 50% and 75%.

[0093] Optionally, a second section restriction Z2 is provided at a second longitudinal position PL2 and a second wave-breaking insert 2'. Such a second wave-breaking insert is shown in dashed line in [Fig.2].

[0094] In this case, a symmetrical behavior is observed for the effects of forward and backward inertial forces on the liquid displacement. The damping function operates identically or very similarly for both directions of opposing forces. Under these conditions, the tank can be transported with either the first end El facing forward or the first end facing backward relative to road transport.

[0095] Specifically, it can be provided that the first position and the second position are symmetrical with respect to a median transverse plane PYZM of the tank (see figures 2 and 4).

[0096] Optionally, a third section restriction Z3 is provided at a third longitudinal position, which can generally be located midway along the length. Such a third section restriction zone at midway along the tank provides a more moderate hydraulic damping effect, but the presence of this third section restriction gives the tank a harmonious appearance and an attractive aesthetic character when viewed from the outside.

[0097] With reference to Figures 3 and 8, at each section restriction, projections of the tank wall towards the central axis of the tank are provided. We have wall projections 81, 82, 83 respectively for the first, second and third section restrictions 71^72,73.

[0098] We can even have more than 3 section restriction zones distributed along the length of the tank.

[0099] A wave-breaking insert can be positioned in each of the section restrictions; however, some of the section restrictions may be without a wave-breaking insert.

[0100] In the case of a wave break insert mounted in a removable manner, a mechanical interface with the bottom of the tank is provided, which will be described later, and a system for retaining the wave break insert from the top, which can take several forms as is now discussed.

[0101] The tank is equipped with a drain valve 61 coupled to an outlet 62, centered on axis XI. Furthermore, the tank is provided with filling ports 63, 64. The bottom of the tank includes ribs and studs 36, 37.

[0102] According to an optional feature, the tank is equipped with a manhole 3.

[0103] The manhole is more concisely called a "manhole", it is preferably arranged on the upper part of the tank.

[0104] The manhole can be closed by a cover 4.

[0105] The manhole can have a round cross-section. The diameter of the passage of the hole The size of a man can be between 40 cm and 50 cm.

[0106] According to another option, the manhole can be of elliptical cross-section.

[0107] The manhole allows access for an operator into the interior volume of the tank, for example to clean the inner walls of the tank, the bottom of the tank, the drain filter or for any other task requiring the presence of a human inside the tank.

[0108] Cleverly, in one embodiment of the present invention, the manhole cover also acts as a retaining element for the upper end of the removable wave-breaking insert.

[0109] However, it should be noted that the presence of the manhole cover is not mandatory; the upper end of the wave-breaking insert can be held in place by a specific shutter. As illustrated by dotted lines 47 in [Fig. 11], the specific shutter is rectangular in shape and represents the cross-section precisely required for inserting and removing the removable insert.

[0110] According to a particular example of a wave break insert 2 shown in Figures 1 to 7. The wave break insert 2 comprises two parallel tubular legs 21, 22 connected by crossbars 23, thus forming a ladder. The tubular legs are in a vertical position.

[0111] The wave break insert 2 is wedged in the lower part via a system of complementary shapes.

[0112] More specifically, the tank bottom 11 comprises two round-section studs 34, 35 with a slight taper. When the wave-breaking insert 2 is lowered into the interior volume of the tank, each tubular leg surrounds a stud, preferably without play, thus immobilizing the tubular leg in X and Y. The lower edge 28 abuts against the stud or the tank bottom.

[0113] Generally speaking, any solution with a male form received in a female form can be suitable for immobilizing the lower end of the wave-breaking insert relative to the bottom of the tank.

[0114] The wave break insert 2 can be formed in the same material as the tank body, i.e. according to a typical example in polyethylene.

[0115] However, since it is a removable insert, it can be made of a different material. Thus, for the recycling step, the insert can be removed before the bare tank body is introduced into a polyethylene recycling circuit.

[0116] The wave break insert 2 could be of any other shape than that illustrated in the figures. In the configuration of the removable wave break insert, however, the corresponding upper opening must allow the wave break insert to be inserted and lowered into its final position.

[0117] One of the advantages of a removable insert is that it can be removed to free up the passage in the internal volume of the tank, in particular if it is necessary to carry out human intervention inside the tank, for example to carry out cleaning.

[0118] Furthermore, the wave-breaking insert 2 can be solid or perforated. For example, in the case of the illustrated ladder-shaped insert, passages 51 are formed between the tubular legs and the crossbeams 23.

[0119] When the manhole has a round cross-section, as illustrated, the cover 4 is generally of revolution about axis Z4. The cover 4 can be secured to the tank by screwing with a helical thread.

[0120] As can be seen in figures 9 and 10, the lid comprises a discoid portion 44 and a cylindrical portion 45.

[0121] The upper portion of the wave-breaking insert 2 comprises a cylindrical portion 25 and a collar 24 which flares outwards from the cylindrical portion 25.

[0122] The mouth of the manhole comprises a cylindrical portion 15 and a shoulder 14 forming the free end of the mouth.

[0123] For the screwing function, a radially external helical thread 46 is provided outside the cylindrical portion 15 of the manhole. A complementary thread is provided in the cylindrical portion 45 of the cover, directed radially inwards.

[0124] Sealing is ensured by a first O-ring J1 interposed between the tank wall and the free edge of the cylindrical portion 45 of the lid. Furthermore, a second O-ring J2 is interposed between the discoidal portion 44 of the lid and the collar 24 belonging to the wave-breaking insert 2.

[0125] An auxiliary plug 48 is provided in the center of the lid. This auxiliary plug may be equipped with a vent function which allows the pressure inside and outside the tank to be equalized.

[0126] As seen in [Fig. 10], the cover 4 may include on the outer rim of the cylindrical portion reliefs 49 which allow a torque to be applied to screw the cover on or unscrew it.

[0127] A second embodiment is now described, illustrated in Figures 12 and 13. A wave-breaking insert 7 is placed in the mold before pouring and mold rotation. The wave-breaking insert can be held in position by shims, which are subsequently replaced by plugs.

[0128] The size of this insert can be quite substantial, because in fact it is not necessary to introduce it into the tank through an opening.

[0129] On the example of insert 7 illustrated in [Fig. 13], it is a flat and perforated partition, reinforced by a horizontal rib 73 and a vertical rib 72.

[0130] The holes 70 can be of small section if it is desired to increase the hydraulic damping effect.

[0131] The insert 7 is secured at the bottom of the tank by means of studs 75 which protrude upwards.

[0132] The peripheral area of ​​the insert is covered by the overmolding 76 of the material of the tank body.

[0133] It should be noted that the tank body advantageously comprises a multitude of ribs, which are in fact stiffening forms, which contribute to the overall strength and rigidity of the tank.

[0134] According to a particular option, visible in Figures 3 and 4, longitudinal reinforcing bars 5G, 5D may be provided, positioned at the top on the sides. The reinforcing bars are arranged outside the internal volume of the tank. in the parts of the external radial projections suitable for housing reinforcement bars, in combination with ties in the form of metal strips 58.

[0135] The reinforcing bars are made of metal and form stiffening stringers.

[0136] Regarding the hydraulic damping function which reduces fluid displacement in response to braking and mitigates the adverse effects on the road handling of the vehicle combination, a restriction ratio SR / ST is defined as the ratio between the reduced cross-sectional area SR and the envelope cross-sectional area ST. The envelope cross-sectional area ST corresponds to the available internal cross-sectional area on the unshaped tubular tank portion that extends towards the center.

[0137] The reduced cross-section SR corresponds to the cross-sectional area of ​​the longitudinal passage with reduced cross-section, reduced by the obstruction opposed by the wave-breaking insert. When the insert is in the plane of the area with reduced cross-section, as illustrated in [Fig. 5], the cross-section corresponds exactly to the liquid passage in that plane. However, an equivalent reduced cross-section can be calculated even if the wave-breaking insert is not strictly in the plane of the area with reduced cross-section.

[0138] The SR / ST restriction rate can be chosen to be between 3% and 50%. Preferably, the SR / ST ratio can be chosen to be between 4% and 33%.

[0139] Even more preferably, the SR / ST ratio can be chosen between 5% and 15%. In reality, the criterion that dictates the choice of the SR / ST ratio can be a maximum filling time or a maximum emptying time of the tank because, in fact, each wave break insert introduces hydraulic damping also in the case of normal tank filling and in the case of normal tank emptying.

Claims

Demands

1. Tank (10) of a capacity of at least 1m3, intended to contain a load of liquid, and intended to be transported by road, said tank being obtained by a rotomolding process using a rotating mold, said tank extending, along a longitudinal axis (X) over a total length (LXT), from a front end (El) to a rear end (E2), the tank comprising at least a first section restriction zone, at a first longitudinal position (PLI) along the longitudinal axis, characterized in that the tank comprises a wave-breaking insert (2;7) mounted in the tank, the first section restriction zone forming a first longitudinal passage with a reduced cross-section at the location of which the wave-breaking insert is placed.

2. Tank according to claim 1, in which the wave-breaking insert is in a longitudinal position (PLA) corresponding to the first longitudinal position (PLI).

3. Tank according to any one of claims 1 to 2, wherein the first longitudinal position is at a first distance DI from the front end, DI being between 15% and 50% of the total length (LXT), preferably between 20% and 35% of the total length (LXT).

4. Tank according to any one of claims 1 to 3, further comprising a manhole (3), preferably on its upper part, which can be closed by a cover (4).

5. Tank according to any one of claims 1 to 4, wherein the wave-breaking insert (2) is removably mounted in the tank.

6. Tank according to claim 5, in which the break-away insert is wedged in the lower part via a system of complementary shapes (21,22,34,35).

7. Tank according to claim 4 and according to one of claims 5 or 6, wherein the cover (4) covers the wave-breaking insert (2) and is connected to the wave-breaking insert.

8. Tank according to any one of claims 1 to 7, wherein the wave-breaking insert (7) is overmolded, the wave-breaking insert being placed in the rotary mold before the pouring of the plastic material.

9. Tank according to any one of claims 1 to 8, wherein a second section restriction is provided at a second position longitudinal (PL2) and a second wave-breaking insert, the first position and the second position being symmetrical with respect to a median transverse plane (PYZM) of the tank.

10. Tank according to any one of claims 1 to 9, wherein a restriction rate SR / ST is defined as the ratio between the reduced section SR and the envelope section ST, the reduced section corresponding to the passage section of the longitudinal passage with reduced section reduced by the obstruction opposed by the wave-breaking insert, the restriction rate being between 3% and 50%, preferably between 4% and 40%, and even more preferably between 5% and 20%.

Images