GB2330170A

GB2330170A - Intermodal tank container with damping device and stiffener

Info

Publication number: GB2330170A
Application number: GB9812979A
Authority: GB
Inventors: Patrick Francis Joy; Martyn Stewart Gill
Original assignee: BRIDELAND SERVICES Ltd
Current assignee: BRIDELAND SERVICES Ltd
Priority date: 1997-10-08
Filing date: 1998-06-17
Publication date: 1999-04-14
Anticipated expiration: 2018-06-17
Also published as: IE81181B1; IES980815A2; GB2330170B; IE980502A1; GB9812979D0; IE980814A1; IES80737B2

Abstract

An intermodal tank container comprises a vessel (2) secured to a a pair of end frames (4) by collars (5). The securing collar (5) is supported unequally against vertical forces by a stiffener (6) fitted at an angle to the collar centre line. Vertical upeard forces are resisted to a lesser degree than vertically downward forces and cyclic loads are thereby dampened. The resistance to static and inertial vertical shear loads, and torsional loads are also improved.

Description

"A Tank Container" Introduction The invention relates to intermodal tank containers used to transport liquids and gases typically by road, rail, and/or ship.

More particularly, the invention relates to intermodal tank containers of the type comprising a vessel which is usually cylindrical with domed ends, a pair of upright end frames, and a connection structure in the form of collars or saddles between the vessel and the end frames.

The vessel is designed within the constraints of International Codes and the frame is usually confined within a format set out in International Standards (ISO). A multitude of different types of connection structures have been developed in an effort to cater for what are essentially conflicting demands of reducing payload and hence costs while providing sufficient strength to resist stresses and loads placed on the structure during handling and transportation.

There is a need for an improved construction of intermodal tank container to withstand not only loads applied during intermodal handling but also loads and stresses applied during transportation.

This invention is directed towards providing such an improved intermodal tank container.

Statements of Invention According to the invention there is provided an intermodal tank container comprising: a pair of end frames; a vessel; a collar connected between the vessel and each end frame; and damping means on at least one of the collars to create a differential between the spring rate acting downwardly and the spring rate acting upwardly to substantially avoid harmonic overload.

Preferably damping means are provided on each collar.

In a preferred embodiment of the invention the damping means comprises a stiffener attached to the collar.

In a preferred arrangement, the stiffener extends at least partially along the collar between the end frame and the adjacent end of the vessel.

Ideally the stiffener is offset with respect to a central longitudinal axis of the vessel.

In one embodiment of the invention the stiffener is offset with respect to the longitudinal axis of the vessel by an angle of from 5 to 85 , preferably by an angle of from 10 to 45 , and, ideally at an angle of approximately 20 according to the duty required by the supports.

In a preferred embodiment of the invention each collar has at least two peripherally spaced-apart stiffeners.

The stiffeners may extend substantially parallel to one another.

Brief Description of the Drawings The invention will be more clearly understood from the following description thereof given by way of example only, in which: Fig. 1 is a side elevational view of an intermodal container tank according to the invention; Fig. 2 is an end view of the tank of Fig. 1; Fig. 3 is a perspective view from one side of the tank; Fig. 4 is a perspective view from the other side of the tank; Fig. 5 is a side elevational view of part of another intermodal container tank according to the invention; and Fig. 6 is an end view of the container tank of Fig. 5.

Detailed Description Referring to the drawings and initially to Figs. 1 to 4 thereof there is illustrated an intermodal container tank 1 according to the invention. The tank 1 comprises a pressure vessel 2, which in this case is of generally cylindrical shape having domed ends 3, and a pair of upright end frames 4. The end frames 4 and vessel 2 are generally of standard construction.

The tank 1 includes a pair of collars 5 which are connected by welding between each end frame 4 and the vessel 2. The collars 5 may be of approximately the same diameter as that of the vessel 2 as illustrated particularly, in Figs. 1 and 2 or may be of smaller or larger diameter than that of the vessel as illustrated in Figs. 5 and 6.

Damping means are provided on at least one, and in this case both of the collars 5 to create a differential between the spring rate (Kg/mm) acting downwardly and the spring rate acting upwardly in order to substantially avoid harmonic overload.

In this case the damping means is provided by at least one, and in this case two stiffeners 6 attached to the collars 5. Each stiffener may be a bar or plate or section made typically of metal, but possibly of any material of suitable strength, and may be attached by welding, bolting or riveting to the collar 5. A stiffener 6 may extend for the length of or only partially along the collar 5. We have found that to avoid harmonic overload it is preferable to offset the stiffener 6 with respect to a central longitudinal axis of the vessel 6. A stiffener 6 may be offset at an angle of between 5 and 85 , preferably at an angle of from 100 to 45 , and ideally at an angle of approximately 20 with respect to the vessel centre axis according to the duty required by the supports.

Each collar 5 may have two or more stiffeners 6. These may be arranged generally parallel with one another or may be relatively offset to maximise the differential between the upwards and downward spring rates.

The invention provides an intermodal container tank which avoids harmonic overload which can result from cyclic loads caused, for example by the swaying of a ship, the tramping of trucks on rutted roads, and the irregular beat of rail joints on a railroad. Typically cyclic accelerations and decelerations of the payload are imported by such motions. The damping means damps such harmonic loads by setting up a differential between the upward and downwards spring rate.

The securing collar 5 is supported unequally against vertical forces by the stiffener 6 being fitted at an angle to the collar centre line. Vertical upward forces are resisted to a lesser degree that vertically downward forces and cyclic loads are damped. Static vertical loads are resisted, and torsional loads are resisted.

The nominally vertical sides of the short collar 5 are put under shear loads by the static weight of the payload and by dynamic vertical accelerations. Excessive vertical shear forces which may be cyclic can cause the collapse of the side curved plates of the supporting collar 5, resulting in the failure of the supporting tube to carry the required load. These excessive forces are in existing practice resisted by increasing the thickness of the collar but the resulting increase in weight is not a preferred solution. Further, the amplitude of the cyclic loads imposed on the frame are increased as the frequency approaches the natural frequency of the combined structure. This will subject the structure to fatigue. The maximum allowable fatigue stress is significantly lower than the yield stress and it is necessary to suppress this cyclic movement.

The positioning of the stiffener 6 at an angle to the vertical extending from the frame side of the collar to the vessel side of the collar 5 or extending only for a part of this distance in order to attenuate the effect or in order to make assembly easier, will support the vessel mass acting in a downward direction to a greater degree than when acting in a generally vertically upwards direction. The collar 5 acts as a spring to reduce shock loads and the effect of the added stiffener 6 will create a different spring rate (Kg/mm) vertically downwards to the effective spring rate vertically upwards, so acting as a damper to the reciprocating movement and protecting the container from sympathetic harmonic overloads. The angle of the stiffener 6 to the horizontal or vertical adjusts the degree of damping or control required and may be positioned at manufacture to any angle other than horizontal or vertical to achieve various degrees of damping and support. The container support structure will therefore better resist norninally vertical cyclic loads.

The damping means may be provided at any suitable location on the circumference of the collar 5 extending from the frame side of the collar to the vessel side of the collar or extending only for a part of this distance in order to attenuate the effect or to make assembly easier. The stiffener 6 enables the collar 5 to resist static or inertial nominally torsional or nominally vertical shear loads which are greater than the rated load-carrying capacity of the structure if the structure was used without this stiffener in place.

Thus, the invention provides an intermodal tank container with substantially improved resistance to harmonic overload. This is achieved costeffectively both in terms of material costs and assembly.

The invention is not limited to the embodiments hereinbefore described which may be varied in detail.

Claims

CLAIMS 1. An intermodal tank container comprising: a pair of end frames; a vessel; a collar connected between the vessel and each end frame; and damping means on at least one of the collars to create a differential between the spring rate acting downwardly and the spring rate acting upwardly to substantially avoid harmonic overload.
2. A tank container as claimed in claim 1 wherein damping means are provided on each collar.
3. A tank container as claimed in claim 1 or 2 wherein the damping means comprises a stiffener attached to the collar.
4. A tank container as claimed in claim 3 wherein the stiffener extends at least partially along the collar between the end frame and the adjacent end of the vessel.
5. A tank container as claimed in claim 4 wherein the stiffener is offset with respect to a central longitudinal axis of the vessel.
6. A tank container as claimed in claim 5 wherein the stiffener is offset with respect to the longitudinal axis of the vessel by an angle of from 5 to 85".
7. A tank container as claimed in claim 5 or 6 wherein the stiffener is offset with respect to the longitudinal axis of the vessel by an angle of from 10 to 450
8. A tank container as claimed in any of claims 5 to 7 wherein the stiffener is offset with respect to the longitudinal axis of the vessel by an angle of approximately 20 .
9. A tank container as claimed in any of claims 3 to 8 wherein each collar has at least two peripherally spaced-apart stiffeners.
10. A tank container as claimed in claim 9 wherein the stiffeners extend substantially parallel to one another.
11. A tank container substantially as hereinbefore described with reference to the accompanying drawings.