ARTICOUPLE & TRIOFIX HOME Types-General Articouple K Articouple F Articouple FR Triofix TK Triofix TR Triofix TRF Pusing at Sea HOME
Cyclic Operation Technicals News Tales InquiriesReference List Reference List History
Types of Mechanical Couplers General Remarks
   Taisei Engineering's mechanical couplers for sea-going pusher-barge systems are classified into two main categories --- 2-Pin supported articulate connection, Series ARTICOUPLE, permitting free relative pitching and 3-Pin supported rigid connection, Series TRIOFIX, not permitting any relative motion, as follows :

2 - Pin Supported Articulate Connection : -
  ARTICOUPLE K Multi-step tooth-engagement,
    F Stepless pure friction-engagement,
    FR Combined friction- and tooth-engagement.
3 - Pin Supported Rigid Connection : -
  TRIOFIX TK Multi-step tooth-engagement (bigger units),
    TR Multi-step tooth-engagement (smaller units),
    TRF Combined friction- and tooth-engagement.

   Each of these types is designed to realize connection practically at any point within the connectable range of draught relationship of the pusherboat and the barge. Further, for simple cases that connection is needed at one point or two points, or even three points, there are much simpler couplers of Series ARTICOUPLE B and TRIOFIX TB.

точечное соединение Articouple ечное соединение Triofix
Image-2a Image-2b
   The ARTICOUPLE-coupler for 2-point supported articulate connection is simpler in construction and the wave-excited load acting on the coupler is generally smaller, and, as the result, the cost is lower. However, it permits free pitching of the pusher relative to the barge and, accordingly, needs some wider clearance between their hulls to avoid hitting of the pusher's stem against the wall of stern notch of the barge. This wide clearance causes heavy eddies which will increase resistance and affect the running speed seriously. The generation of eddies in the barge stern is the very reason why the speed of the pusher-barge train is unexceptionally lower than the speed of a conventional ship of same loading and same engine power. In addition, the pusher swung by the oscillating barge is subjected to heavy pitching and, as the result, the articulately connected pusher cannot be a ship comfortable to the crew on board.
   On the contrary, the rigid connection by TRIOFIX 3-point supporting coupler does not permit any relative motion of the pusher and the clearance between two hulls can be reduced to the minimum to lower the eddy resistance remarkably. Therefore, the 3-pin supported rigid connection involves a possibility of getting a much higher propulsive performance - speed - than the 2-pin supported articulate connection, and this is important particularly when higher speed is desired in longer routes. Further, absence of relative pitching assures a same comfortableness to the crew on board as a conventional self-propelled ship.
   But, on the other hand, the TRIOFIX-coupler has a greater number of components and the wave-excited load acting on the coupler is generally larger and, as the results, the cost is somewhat higher. In addition, the barge with rigidly connected pusher must have a greater longitudinal strength than a barge with articulately connected pusher, because the former, in combination with the pusher, will move as a single body in waves. Thus, the rigidly connected pusher-barge train having a better operational performance is somewhat more expensive in building cost inevitably. But, if an excellent propulsive performance can be realized through adopting good hull forms, the engine power required for getting a same speed can be reduced or a higher speed can be got with a same engine power, and such an excess performance is often more than sufficient to cover the difference of the building cost.
   When running in waves, the characters of wave-excited loads are much different between 2-pin supported articulate connection and 3-pin supported rigid connection, and the coupler constructions should be adapted to such different characters of the loads. Further, the coupler load varies with the longitudinal position of the coupler main bodies on the pusher hull. In 2-point supported articulate connection, if the coupler position is moved aft to get near amidships, the longitudinal load component will decrease and the vertical component will increase, and the pitching angle will increase as the coupler position approaches amidships --- nearer to the centre of gravity. Therefore, 100% advantage is not probable. In 3-pin supported rigid connection, somewhat similar variations of coupler loads occur.
   Types having friction-components, having names with "F", can permit "Draught-adjustment" during cargo-handling work so that the draught of the pusherboat can be adjusted, manually or automatically, while the draught of the barge gradually changes due to loading or unloading and the pusherboat can remain connected while cargo-handling. These couplers with F can also be used for operating dumping barges which will change draught abruptly when dumping load, while the pusher can be kept connected to the barge. Another merit of the friction-connection is that the connection is "stepless" and F- coupler can realize connection under influence of waves of a certain height.
   For simple transport services among sheltered harbours, it is recommended to use types without "F" (friction component) because the models with "F" have, as their vital components, "Pressing shoes" with high-friction rubber lining which needs periodical replacement at intervals of several years, depending on the roughness of use, and this replacement needs high-grade technique and a certain cost. Couplers without "F" have no parts needing such a periodical replacement, while the pusherboat must be kept disconnected during cargo-handling in harbours.
   The couplers with friction components have some limits to their realizable sizes. ARTICOUPLE - K and TRIOFIX - TK series of pure tooth-engagement principle have no such limit of size, and they are the most reliable couplers suitable for big sizes applied to long-distance services in rough sea.
   As for the navigability in rough sea, the rigid connection with TRIOFIX-coupler might, at a glance, seem superior to the articulate connection with ARTICOUPLE-coupler. In practice, however, these two series can realize a same level of seaworthiness if the model is properly selected on the basis of reliable analysis of coupler loads and the pusherboat and the barge are properly designed.
   As may be obvious from the above explanations, Taisei Engineering's ARTICOUPLE and TRIOFIX can cover all probable types of needs for the pusher-barge systems, and the above-mentioned various models were developed for the purpose of complying with multifarious types and modes of demands addressed to the manufacturer.
   The coupler model should be selected to suit to the character and use of the barge and, then, to keep necessary navigability in the probable heaviest sea state expected in the service routes or areas intended.
   The following pages will state details of the above-mentioned various types.

HOME Copyright Next