GB1593812A - Device for inverting the direction of rotation of a driven shaft - Google Patents

Description

(54) DEVICE FOR INVERTING THE DIRECTION OF ROTATION OF A DRIVEN SHAFT (71) We, FRANCO Tosi S.p.A., a Company recognised by Italian Law, of Via Brisa 3, Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The device the subject of the present invention has been envisaged in connection with the problem of the reversing the motion of a driven shaft while keeping the motion of the driving shaft both unaltered and uninterrupted.

As a nonlimiting particular case, there shall be examined herein the application to the problem of the reversal of the direction of rotation of the propeller of a ship in which the prime mover is constituted by nonreversible Diesel engines or gas turbines, and, in general by machines which cannot have their direction of rotation reversed.

The system which is commonly used for inverting the direction of rotation of a driven shaft is a mechanical system. The driving shaft can be connected to the driven shaft either directly or by the intermediary of an inversion gear train (inverter). The transition from the direct control on the inverter and therefrom takes place by means of clutching devices of various make, of the disconnectable type, such as clutches, friction clutches, hydraulic joints. This approach, which can easily be embodied if the power values involved are not exceedingly high, becomes obtrusive, bulky and inconvenient and costly when powers are involved in the order of magnitude which is common in the marine engines. This approach becomes still more objectionable if the inertia of the driven shaft is considerable since, if so, the power which must be destroyed by the clutching member when the direction of motion is reversed to bring the driven shaft to the same RPM of the driving shaft, may attain such high values as to overheat the mechanical component parts and thus as to damage them.

The reversal of the direction of rotation of the propeller(s) for ships having fixed-pitch propellers is necessary for two reasons, viz.: a) To enable the ship to go astern even for a long time with the propellers being rotated to a speed of rotation up to 70% of the top RPM. The power delivered under such conditions attains about one third of the maximum power ahead; b) to permit the quick stop of the ship (anticollision run) by the braking action of the propeller which is rotated backward to 50% of its maximum RPM whereas the ship as itself, due to its inertia, continues to go ahead. For the latter operation, a torque is required which is 80% of the maximum power ahead.

The problem has been solved long since in a satisfactory way for the steam propelled ships by adding to the steam turbine a specially provided set of astern-run vanes.

The same problem has been solved, even through not so satisfactorily, for the ships propelled by Diesel engines, by providing reversible Diesels which are yet capable of delivering their power in both the directions of motion. Such reversibility, in fact, permits that the manoeuvers indicated under a) above may be carried out satisfactorily but the manoeuvers indicated at b) above can regrettably be effected with less satisfactory results. As a matter of fact, the engine cannot be started astern unless it has been stopped before. In the astern starting stage, the torque is produced, rather than by the engine, by the starting device of same. In addition, the Diesel engines, inherently, cannot stably be rotated below the minimum RPM: these are roughly in the order of 55% of the maximum RPM.

On ships to which a very high manoeuverability is required, Diesel engines of the nonreversible type are frequently adopted, which are coupled to variable-pitch propellers.

The problem, however, appears to have been solved less satisfactorily in the case of the propelling system with gas turbines only, since the market does not tender, at present, reversible gas turbine engines, even though it is known that many manufacturers have put such a study in programme. It has been recently suggested to superpose astern-run vanes to the conventional ahead-run vanes of the gas turbine. In such a case, by baffling the gas stream towards the former, or the latter vanes. it becomes possible to revert the motion of the driven shaft. Such an approach, however, involves a greater intricacy in component parts which are inherently intricate and also a deterioration of the efficiency during the normal operation of ahead motion, due to the losses of gas on the baffling means and the weakening of the gas stream on the additional vanes.

Consequently, up to the present days. the problem of the gas turbine propulsion systems has been solved, as a rule, by adopting variable-pitch propellers, or, as an alternative, with inverting gears. The variable-pitch propellers, anyhow, have the defect (as compared with the fixed-pitch propellers) of a higher first cost, a greater propeller hub diameter and a decrease of the propelling efficiency of the propellers along with the necessity of docking the ship for repair, checkout and inspection of the vane control mechanism.

As a result of such shortcomings, the examples are numerous of gas turbine propelling systems with fixed-pitch propellers and inverting gear trains, in which the turbine controls the reducing gear either directly or via an inversion gear train.

In order that the transition from the direct drive to the drive with the intermediary of an inversion train, there is used either a pair of disc friction clutches or a pair of disconnectable hydraulic couplings. By so doing, if either component of the pair is inserted and the other is cleared, and vice versa, it becomes possible to invert the direction of rotation of the propeller(s). Whenever disc friction clutches are used, it has been seen that, in the manoeuver of rapid stop from the maximum speed, difficulties arise which derive from the considerable amount of heat that the friction clutch is requested to disperse. More particularly, the friction clutch, which is generally air-cooled, attains a very high temperature and the contacting surfaces wear considerably.

To this defect, there must be added the intricacy and the cost of the train of inversion gears.

If, instead of two friction clutches, two hydraulic couplings are used, by filling either coupling with oil and dumping the oil from the other, the manoeuvers can be completed.

The dissipation of the heat evolved in the ship quick-stop operation is entrusted to the oil which fills the coupling.

Such a system is completed by a selfsynchronizing coupling which connects the gas turbine directly to the gears of the reduction train, by bypassing the ahead run hydraulic coupling during the normal navigation, thus preventing the power loss which corresponds to the efficiency of such a coupling.

The knowledge acquired in the construction of power systems for ships of which a high manoeuverability is required, such systems comprising Diesel engines, Gas-turbine Diesels, or Steam turbines, as well as the results of the tests made all over the world, have shown that the ideal prerequisites for a hydraulic device for the reversal of the direction of rotation of a propeller are as follows: I) Simplicity in construction, as achieved by limiting the number of the component parts; 2) Possibility of quickly and reliabily inserting the hydraulic coupling and of rapidly and surely deactivating the direct control so as to effect the quick stoppage of the ship; 3) Ability of dispersing the heat by the coupling so as to permit that the ship concerned may be stopped without overheating the coupling and the oil contained therein; 4) Possibility of emergency action in the case of failure of the hydraulic coupling and the self-synchronizing coupling; 5) Convenient access to the component parts of the inverter for possible repair, checkups and overhauling without being compelled to dock the ship.

A principal object of the present invention is just to provide a hydraulic device for the reversal of the direction of rotation of a driven shaft, more particularly for driving fixed-pitch propellers on board ships driven by nonreversible internal combustion engines, so as to make it possible to fulfil the above enumerated requirements.

The present invention provides a hydraulic coupling device for transferring rotational drive from a driving shaft to a driven shaft, comprising a driving cup and a driven cup, and a set of flow-diverting vanes associated with the cups to establish fluid flow between the cups and rotation of the driven cup responsive to rotation of the driving cup, the vanes being in fluid communication with an annular channel defined between said cups and having first positions relative to said channel establishing a first direction of rotation of the driven cup relative to the driving cup and second positions relative to said channel establishing a reverse direction of rotation of the driven cup relative to the driving cup, wherein said vanes in said first positions are located externally of said channel and in said second positions are located internally of said channel and are radially movable between said first and second positions under the control of respective actuators.

The invention will be described in greater detail with reference to an exemplary embodiment thereof, as illustrated in the accompanying drawings, in which: FIGURE 1 is a cross-sectional view show ing a hydraulic coupling device in accordance with the invention as practically applied to the field of the marine propulsion systems; FIGURE 2 is a closeup view showing the baffling set of vanes of the device in a working condition other than that depicted in FIG. 1, and FIGURES 3 and 4 are two cross-sectional views, taken along the lines III--III and IV-IV of FIGURES 1 and 2, respectively.

Having now reference, at the outset, the FIGURE 1 of the drawings, the coupling device in accordance with the invention is structurally composed by a driving cup 1, which is rigidly connected to a driving shaft 2, by a driven cup 3, rigidly connected to a driven shaft 4, by an outer casing 5, capable of withstanding the oil pressure, and by the reversing set of vanes 6, equipped with its control servomechanism, the latter consisting of a set of respective hydraulic jacks 7. The vanes 6 are in fluid communication with an annular channel defined between the cups, and are radially movable into and out of the channel by the jacks 7.

The assembly is then completed by an oil pump 8 for filling the coupling and by a telecontrolled valve 9, intended to regulate the quantity of oil which must flow into the coupling so as to disperse the calories generated in and by the coupling.

By the intrumentality of the servomotor 7, the set of reversal vanes 6 can take two different positions, viz.: a first position, shown in FIGURES 1 and 3, in which the set of vanes, being located externally of the annular channel between the cups 1,3, does not disturb the flow of the oil stream between 1 and 3, so that the driven cup 3 is rotated in the same direction as the driving cup 1, as indicated by the arrows F of FIGURE 3, and, a second position in which the set of vanes, conversely, being located internally of said annular channel, deflects the oil stream in such a way that the driven cup 3 is rotated in the opposite direction to the driving cup 1, as indicated by the arrows F, and F2 of FIGURE 4.

By acting upon the servomotor 7, it is thus possible to obtain that, while the driving shaft 2 rotates constantly in the same direction of rotation, the driven shaft 4 can be rotated in either of two opposite directions of rotation.

The heat generated during progress of the reversal manoeuver is removed by the oil which flows through the coupling. By conservatively sizing the oil pump 8 and the dump valve 9 it is possible to cope with those emergencies in which the heat build-up is exceptionally high.

A particular application has been studied for the case in which, for a marine propulsion system, there are the following requirements to fulfil: a) To disperse a considerable amount- of heat during the reversal of the direction of motion of the ship, as due to the inertia of the driven shaft or to other reasons; b) directly to connect the driving shaft to the driven shaft so as directly to suppress the loss of efficiency of the hydraulic coupling during long period of time in which no reversal manoeuvers are required, and c) rapidly to undo the direct connection between the driving shaft and the driven shaft so as to be able to effect sudden manoeuvers which might become necessary.

For such a special application, the reversal system is composed by: -a reversing hydraulic coupling of the kind described hereinbefore; -a self-synchronizing coupling of conven tional make and capable of stably connect ing the driving shaft to the driven shaft; -an oil-feed system for the reversing cou pling.

In the particular case of the propulsion of watercraft, it has been deemed appropriate that the hydraulic coupling is not sized to transfer the entire power from the engine (prime mover) but only the power which is required during progress of the manoeuver.

By so doing, it is possible to confine both the bulk and first cost of the coupling within more reasonable boundaries, for the normal course, there will be used the self-synchronizing coupling which, capable as it is of being inserted into action at the completion of the manoeuvers without having to stop the engine, will directly connect the driving shaft to the driven shaft. Under such conditions of operation, the oil pump for filling the joint can be stopped in order to prevent an unnecessary power useup.

It is important to note that, if the pump is kept running for special requirements (such as navigation in the fog) there would not be any stream power losses in the interior of the coupling since the two cups, the driving one and the driven one, are rotated as an entity while, as is known, the power losses in the hydraulic couplings are proportional to the rotation speed differential between the two cups. In FIGURE 1 there is shown by way of nonlimiting example an application of the kind referred to above which is particularly suitable for the marine propulsion with gas turbines and more particularly for propulsion with nonreversible engines.

In such illustration, a non-reversible engine 10 controls through a double-reduction reducing gear train (couples of gears 11, 12 and 13, 14) a driven axle 15, which in the case of marine propulsion, is the axle of a fixed-pitch propeller.

On the axle of the gear 12 there is arranged the reversal hydraulic coupling described above, the driving cup I of which is rigidly connected to the gear 12, whereas the driven cup 3 is rigidly connected to the gear 13. The driving cup I can thus be directly connected to the gear 13 by means of a self-synchronizing coupling 16 and. if so. the driving cup I, the gear 13 and the driven cup 3 are rotated in unison together.

Finally, although the arrangement shown in the drawings has been particularly described with reference to a marine propulsion system, the invention can be applied also to fields other than that of marine propulsion.

in cases in which a sudden inversion of the direction of motion is necessary for a shaft which is driven by a non-reversible prime mover.

WHAT WE CLAIM IS: 1. A hydraulic coupling device for transferring rotational drive from a driving shaft to a driven shaft, comprising a driving cup and a driven cup, and a set of flow-diverting vanes associated with the cups to establish fluid flow between the cups and rotation of the driven cup responsive to rotation of the driving cup, the vanes being in fluid communication with an annular channel defined between said cups and having first positions relative to said channel establishing a first direction of rotation of the driven cup relative to the driving cup and second positions relative to said channel establishing a reverse direction of rotation of the driven cup relative to the driving cup, wherein said vanes in said first positions are located externally of said channel and in said second positions are located internally of said channel and are radially movable between said first and second positions under the control of respective actuators.

2. A device according to CLAIM 1, characterized in that between the driving cup and the driven shaft a direct-drive linkage is provided with a self-synchronizing coupling inserted therebetween.

3. A device according to CLAIM 1, as applied to the drive of propellers actuated by non-reversible engines.

4. A device according to the preceding claims, substantially as hereinbefore described and illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. connected to the gear 12, whereas the driven cup 3 is rigidly connected to the gear 13. The driving cup I can thus be directly connected to the gear 13 by means of a self-synchronizing coupling 16 and. if so. the driving cup I, the gear 13 and the driven cup 3 are rotated in unison together. Finally, although the arrangement shown in the drawings has been particularly described with reference to a marine propulsion system, the invention can be applied also to fields other than that of marine propulsion. in cases in which a sudden inversion of the direction of motion is necessary for a shaft which is driven by a non-reversible prime mover. WHAT WE CLAIM IS:

1. A hydraulic coupling device for transferring rotational drive from a driving shaft to a driven shaft, comprising a driving cup and a driven cup, and a set of flow-diverting vanes associated with the cups to establish fluid flow between the cups and rotation of the driven cup responsive to rotation of the driving cup, the vanes being in fluid communication with an annular channel defined between said cups and having first positions relative to said channel establishing a first direction of rotation of the driven cup relative to the driving cup and second positions relative to said channel establishing a reverse direction of rotation of the driven cup relative to the driving cup, wherein said vanes in said first positions are located externally of said channel and in said second positions are located internally of said channel and are radially movable between said first and second positions under the control of respective actuators.

2. A device according to CLAIM 1, characterized in that between the driving cup and the driven shaft a direct-drive linkage is provided with a self-synchronizing coupling inserted therebetween.

3. A device according to CLAIM 1, as applied to the drive of propellers actuated by non-reversible engines.

4. A device according to the preceding claims, substantially as hereinbefore described and illustrated in the accompanying drawings.