Land vehicles – Tank or boiler – Tank truck
Reexamination Certificate
2000-10-30
2003-05-06
Johnson, Brian L. (Department: 3618)
Land vehicles
Tank or boiler
Tank truck
C280S839000, C105S358000, C220S562000
Reexamination Certificate
active
06557896
ABSTRACT:
DESCRIPTION
The present invention relates to road and rail tankers.
Tankers are widely used for transporting liquids and in the case of road transportation, numerous designs of tank have been produced to suit so called rigid chassis vehicles which are self powered and semi trailers which are pulled by a tractor unit, and drawbar trailers
The earliest designs comprised a single tank mounted on the chassis of a vehicle or trailer. Most tanks are formed with an integral longitudinal sub-chassis by which the tank is secured to the chassis of the vehicle or trailer. The typical vehicle chassis is of ladder construction and in practice is anything but rigid. Indeed it is intended to allow considerable flexing of the chassis, especially along its length, to accommodate variations in ground level.
When a tank is secured to a rigid vehicle chassis, the usual approach is to secure it positively using nuts and bolts connecting the chassis and the tank sub-chassis at several positions along its length. Usually a thin layer of rubber or felt is positioned between the respective chassis members to prevent rubbing due to metal to metal contact. This intermediate layer maybe of the order of 10 mm thick at most, often less, and offers little if any resilience.
As a consequence of the presence of the securely mounted tank the assembly is considerably stiffer than the chassis itself.
Most tanks are subdivided into a series of separate compartments each with their own inlet and outlet. This enables different liquids to be carried. For example in the case of fuels or lubricants, different grades of fuels or lubricants can be carried in the one vehicle.
However, these multi-compartment tanks are known to suffer from cracking of one or more of the internal dividing walls, even the outer walls of the tank shell. This results in contamination of the contents of one compartment with those of another and/or leakage of the contents. This needs to be avoided. The tanks have to be checked regularly to ensure integrity of each compartment. Gas pressurisation testing is the most reliable.
The cracking is believed to arise because of the repeated stressing of the tank due to the motion of the vehicle in use. Since the vehicle chassis or trailer chassis is less rigid than the tank any forces which cause twisting of the chassis will be transferred into the tank. However, the tanks are not able to resist these repeated twisting forces hence the above problem with cracking of the internal dividing walls and/or the external shell.
One attempt to try and solve this problem in the case of a rigid vehicle tank has been to mount the sub-chassis of the tank rigidly to the chassis of the vehicle at the rear of the chassis and to mount the other end of the tank chassis to the front of the vehicle chassis by way of over length bolts having coil springs applied about the shanks under the nuts to allow some movement of said end of the tank. This known arrangement allows approximately 25 mm of movement before coil binding but has not proved a solution to the problem. There is nothing against which the bolts can be tightened in this type of mounting.
It is believed that the flexing of a vehicle chassis or trailer can be in excess of 150 mm over the length of a typical chassis. Allowing for such a range of movement has not proved possible with the aforementioned proposals and consequently the problem of internal cracking remains.
The present invention aims to provide a solution.
Accordingly, a first aspect of the invention provides a road or rail tanker comprising a wheeled chassis and a plurality of tanks disposed in series one behind the other and wherein the plurality of tanks are individually mounted on the chassis each using a plurality of flexible mounts.
Each flexible mounting needs to allow at least upward and downward movement of the tank relative to a rest position so that twisting forces are not imparted directly to the tank. By using a plurality of tanks set along the length of the chassis, each tank mounting only has to be capable of accommodating a proportion of the total potential twisting movement of the chassis. A flexible mounting can be readily constructed to allow such amounts of movement while providing adequate support for the tank. The sort of amounting used for securing engines in the chassis of road vehicles can be readily adapted for this purpose. These allow movement in all directions relative to a rest position.
Each tank is able to move independently on its mountings and thereby accommodate the movement of the chassis at that location.
The tanks will be spaced apart in the longitudinal direction by an amount necessary to accommodate the permissible range of movement of each tank as the chassis twists and bends. As the movement of the chassis is not usually pure bending, but twisting, the tanks can be relatively close together than might otherwise be thought to be the case. The separation of the tanks is seen as aesthetically unpleasing and optionally the gap may be obscured by providing a continuity element. In one embodiment this is in the nature of a resilient plastic or rubber material, conveniently a length of flexible tube or piping, which at least extends down each side of the tanks at a position between the individual tanks. It is not necessary for the continuity element to be applied to the top or the base where it would not be visible to the casual observer. The gap between the tanks can provide a useful storage location for dip rods, air pipes, vents and wires. The continuity element may comprise a flat strip which is dimensioned to bridge the gap between the tanks and overlies the surface of the adjacent tanks. It may be secured to one of the tanks or be of a H-section to fit around respective end of flanges of the tanks. It may snap fit onto one of said flanges.
The preferred flexible mount comprises a resilient element made of rubber or the synthetic equivalent having a central bore receiving a metal sleeve. The resilient element is accommodated within a mounting flange to which it is secured by vulcanising, bonding or the like. The resilient element extends to both sides of the mounting flange. In use the mounting flange is interposed between flanges carried by the tank and the vehicle/trailer chassis such that a portion of the resilient element is under compression and a further portion projects through a hole in one of the flanges and is prevented from pulling through by a metal washer applied to the end thereof. A bolt passing through the assembly and carrying a nut to its other end secures the flexible mounting between the respective flanges of the chassis parts allowing relative movement of the tank with respect to the vehicle/trailer chassis. This construction allows the bolt to be fully tightened. It is preferred to provide at least
4
mountings for each tank. The number could be increased to carry heavier weights or individual mountings could be beefed up. Tanks that are at present made of steel to better withstand the imposition of bending and twisting forces could now be made of light alloys, such as aluminium. The reduction in weight will enable the tanks to be larger, thereby permitting increased quantities of liquid to be carried without increasing the overall vehicle/trailer gross weight.
The wheeled chassis may be a four, six or eight wheeled rigid self powered road vehicle, or a draw bar trailer, or an articulated semi-trailer for the road. There are advantages in the case of a semi trailer if the chassis, when connected to the tractor unit, can slope downwardly to the wheels of the trailer. For example it permits greater vertical articulation, i.e. downward movement of the trailer unit with respect to the trailer. However, such a construction when used with conventional multi-compartment tankers of the type where each compartment has to have a calibrated dip rod has problems as the inclination will result in a lack of horizontal symmetry and consequently the dip rod readings will be inclination dependent. However, this problem can be overcome when a plurality of sep
Borttoff Christopher
Drinker Biddle & Reath LLP
Johnson Brian L.
LandOfFree
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