The present invention generally relates to launch and retrieval systems suitable for handling loads such as lifesaving equipment.

The invention may be applied to lifesaving systems including lifeboats that are to be lowered to, and retrieved from, the surface of the sea from vessels or rigs and the like.

More particularly, the present invention relates to an emergency launch system for a lifeboat where the system is operated by means of a hydraulic system.

According to a first aspect, the present invention relates to a hydraulic launch system for a lifeboat. The hydraulic launch system includes a motor configured for, during launch operation, establishing a flow of pressurized hydraulic fluid in the hydraulic launch system.

According to a second aspect, the present invention relates to a method of cooling hydraulic fluid or oil in a hydraulic system or subsystem configured for launch of a lifeboat.

It is understood that the expressions rig, platform, ship, boat or vessel, throughout this specification, are meant to denote any kind of maritime structure, floating or not, suitable for carrying persons, cargo or a combination thereof.

It is further understood that the expression fall, throughout this specification, is meant to denote any kind of wire or rope which is suitable for being wound up on, or wound from, a drum.

Background

Lifesaving systems shall, according to today's rules and requirements, be prepared and configured for deployment under conditions wherein their place of application is not able to provide power. Such conditions are often called "dead-ship", "powerless- rig" or simply no-power conditions.

Today's lifesaving systems are therefore provided with means allowing for

reasonably controlled launch and descend of lifeboats even though their place of installation supply no power.

In addition to the systems being configured for launch under no-power conditions, the systems has to be failsafe meaning that redundancy is required by the launch systems.

Background art

An early and simple launch system configured for no-power and failsafe launch includes a winch provided with a pure mechanical centrifugal brake configured to apply increasing brake force as a function of a lifeboats speed of descend. The centrifugal brake gave rise to severe heat and durability problems as well as proved to be difficult to maintain in proper operating condition in harsh marine environments.

More resent systems achieved no-power and/or failsafe operation by means of applying, to a part of the system, either an electrical source of emergency power, such as a battery or UPS, or applying pressure accumulators configured to store pneumatic or hydraulic energy. These systems typically includes a winch provided with a brake disc and a brake caliper, where the brake caliper, in no-power or emergency/failsafe conditions, is operated by an emergency power supply system.

The more recent brake disc based launch systems are considered efficient launch systems, however the systems suffer from various drawbacks; some of which are:

- that the brakes are considered difficult to maintain in proper operating

condition in harsh marine environments, - that the brakes take up substantial space. Compact installations are required where the entire lifesaving system is to be encased in an encasement or equivalent,

- that the brakes tend to overheat, and ultimately fade, if the load to be

launched is very heavy or the load is lowered from extreme heights such as from very high ships or rigs,

- that the brake disc requires subtle control which has been proven difficult to establish in no-power operation.

Manufacturers of lifesaving equipment therefore seek alternative emergency launch systems configured to meet or solve one or more of the abovementioned drawbacks while also providing failsafe operation.

It has been found that replacing the disc brake with a hydraulic motor configured for controlling the speed of descent by means of converting the potential energy of the lifeboat into hydraulic flow, and ultimately heat, is attractive as the relatively small hydraulic motor generally solves the abovementioned drawbacks - provided sufficient cooling of the hydraulic oil is established.

Cooling of the hydraulic oil could be provided by applying hydraulic oil coolers in combination with a number of ventilators; however such cooling installation require power, space and maintenance, hence this solution is considered inadequate.

JP 1 1 130381 A discloses a brake hydraulic pump connected to a lifeboat winch drum via a one-way clutch. The brake hydraulic pump is driven by the winch drum during free-fall running. By supplying the discharge oil of the pump to the cylinder of a hydraulic brake, in order to apply a braking force on the winch drum, the free-fall speed is regulated. Also, by supplying discharged pump oil to a brake heat generation part through a cooling pipeline, the brake heat generation part is cooled. The object of the disclosure is to regulate a free-fall speed while securing an original free-fall function. US 5709085 A discloses a method of cooling hydraulic oil present in an operating circuit of a construction machine. Further, the reference discloses an installation for cooling hydraulic oil according to the method. The method includes steps of leading the hydraulic oil at least partially over an oil cooler and thereafter causing the hydraulic oil to flow into a hydraulic oil tank. The hydraulic oil is pumped from an intermediate reservoir to an oil cooler for lowering the temperature of the hydraulic oil prior to causing the hydraulic oil to flow into the hydraulic oil tank. The hydraulic oil is then caused to flow into the hydraulic oil tank from the oil cooler for mixing the hydraulic oil flowing into the hydraulic oil tank from the oil cooler with the hydraulic oil present in the hydraulic oil tank. The hydraulic oil flowing into the hydraulic oil tank from the oil cooler has a temperature different from the temperature of the hydraulic oil present in the hydraulic oil tank.

Brief description of the invention

The abovementioned reference suggest cooling of hydraulic oil by means of a relatively complex and large oil cooling system which is not configured for cooling under scenarios wherein the place of installation offers no power.

The present invention seeks to set forth a compact and failsafe launch system for a lifeboat including a hydraulic subsystem configured for emergency launch of a lifeboat under scenarios wherein the place of installation offers no power.

Up to this day, prior art has failed to teach a simple and yet reliable and inexpensive launch system which in a safe and reliable manner, without substantially increasing particulars of the system, provide a reliable and durable launch system allowing for a virtually maintenance free and compact installation.

According to the invention, there is provided a hydraulic launch system as per the introductory part of this specification wherein the system further includes a cooling circuit provided with hydraulic fluid injecting means configured for diverting heat from the flow of hydraulic fluid. The heat is diverted by means of exchanging, or replacing, a portion of the hydraulic fluid flowing through the cooling circuit. The hydraulic fluid injecting means includes means configured for increasing the velocity of the flow of hydraulic fluid between a nozzle portion and an injector bore whereby a low pressure zone is created such that hydraulic fluid is drawn into the cooling circuit via the injector bore.

The means configured for diverting heat from the hydraulic fluid or oil by means of exchanging or substituting a portion of the hydraulic oil flowing through the cooling circuit may constitute a passive component, i.e. a component configured for powerless operation. This provides a simple way of obtaining efficient cooling of the hydraulic oil, and further, the means allows for failsafe launch of means for lifesaving even in no-power conditions.

According to one embodiment, the flow may, in order to control the speed of the motor, be lead through means for controlling the rate of flow of hydraulic oil through the motor. The means could include various forms of restrictors which may or may not be incorporated into the hydraulic motor. Further, the motor could be any kind of variable displacement motor.

According to one embodiment, the hydraulic oil injecting means may include an injection unit configured for exchanging a portion of through flowing hydraulic oil with hydraulic oil having a temperature that is lower than the temperature of the hydraulic oil flowing towards the injection unit.

According to one embodiment, the hydraulic oil injecting means may include means configured for increasing a velocity of the hydraulic oil between a nozzle and an injector whereby a low pressure zone is created such that hydraulic oil is drawn into the cooling circuit.

According to one embodiment, the hydraulic oil injecting means configured for diverting heat from the hydraulic oil by means of exchanging a portion of the hydraulic oil may be configured for maintaining an inlet of the motor pressurized such that cavitation and boiling etc. is avoided. Alternatively, the cooling loop may be provided with means such as a nozzle or equivalent configured for maintaining positive pressure in the system downstream the oil injecting means. The positive pressure may, in both embodiments, be kept above 1 .5 bar, preferably about 2 bar.

According to one embodiment, the hydraulic oil may be exchanged with hydraulic oil stored in a hydraulic oil system storage tank.

According to one embodiment, the system storage tank may be ventilated at ambient pressure.

According to one embodiment, the system storage tank may be ventilated with pressurized air such that a certain excess pressure is maintained in the system whereby cavitation may be prevented.

According to one embodiment, the hydraulic oil injecting means may be located inside a hydraulic oil system storage tank leading to a compact and efficient system.

According to a second aspect of the present invention, a method of cooling hydraulic oil of a hydraulic subsystem configured for launch of a lifeboat is provided. The method includes the steps of:

- during launch operation, establishing a flow of pressurized hydraulic oil by means of rotating a hydraulic motor,

- leading the flow of pressurized hydraulic oil through a cooling circuit, and

- diverting heat from the hydraulic oil by means of exchanging a portion of the hydraulic oil flowing through the cooling circuit while maintaining positive pressure on an inlet of the hydraulic motor.

Brief description of the drawings

Figure 1 shows in part a principal diagram of a hydraulic system according to the present invention. Figure 2 is a sectional view through a part of means for exchanging a portion of hydraulic oil flowing through a cooling circuit.

Detailed description with reference to the figures

Figure 1 shows in part a principal diagram of a hydraulic system.

As can be seen in figure 1 , conduits 20, together with an injection unit 50 and a hydraulic motor 10, form, partially or not, a loop wherein hydraulic fluid or oil circulates during launch of a not shown lifeboat.

The lifeboat is suspended from one or more falls 5 wound on a drum forming part of a winch 6 connected to a hydraulic motor 10.

The object of the hydraulic motor 10 is to limit the maximum speed of the winch 6 in case the primary brake system for some reason fails.

When a lifeboat is suspended from one or more falls 5 in a stationary condition, brake means 7 prevent the winch 6 from rotating.

During launch operation, the brakes 7 are released allowing the weight of the lifeboat to rotate the winch 6 whereby torque is transferred to the hydraulic motor 10. The torque may, as shown in figure 1 , be transferred directly to the hydraulic motor 10. Alternatively, the torque may be transferred to the hydraulic motor 10 or via one or more not shown gears.

During launch operation, the lifeboat is lowered from an elevated position down to the surface of the sea. The potential energy, or height energy, stored in the lifeboat is transferred, via the hydraulic motor, to the hydraulic oil. The energy causes the hydraulic oil to circulate in the loop. In order to control the speed of descend of the lifeboat, the circulation is controlled by means flow restrictors 21 or equivalent which may or may not be part of the hydraulic motor.

The restriction of flow natively heats up the hydraulic oil. During descend of the lifeboat; the hydraulic system is, according to one aspect of the present invention, cooled by exchanging a part of the hot hydraulic oil with hydraulic oil having a lower temperature. The exchange of hydraulic oil may be performed by means of the injection unit 50.

Referring to figures 1 and 2, the injection unit 50, or the hydraulic oil injecting means, may include an injector 51 comprising means configured for increasing the velocity of the flow of hydraulic oil between a nozzle portion 54 and an injector bore 52 whereby a low pressure zone is created such that hydraulic oil may be drawn from the injector bore 52 and into the stream of hydraulic oil, and thereby the cooling circuit.

The injector bore 52 may be configured to be in fluid communication with hydraulic oil stored in a tank.

As can be seen in figure 1 , the injection unit further may be provided with a pressure control conduit 53 provided with a flow restrictor configured to control the pressure in the loop or circuit.

Emergency launch of a lifeboat via the system according to some embodiments of the present invention may be accomplished by means of manual activation and control of the launching sequences.

The launching sequences include the steps of:

- repositioning the lifeboat or lifeboat encasement, and

- subsequent launch of the lifeboat, possibly out underneath an enclosure.

Repositioning of the lifeboat or lifeboat encasement may entail operating davits such that the lifeboat or lifeboat encasement is relocated from a stowed position, possible on a deck, to a position wherefrom the lifeboat may be lowered to the surfaced of the sea. The emergency launch may be performed by operating handles positioned near the lifeboat from inside the lifeboat. The handles may be positioned inside an enclosure accommodating the lifeboat.

The sequence of launching the lifeboat from inside the lifeboat may include:

- opening a hatch on the lifeboat,

- through the hatch, operate a first valve via a first handle (possibly by initial removal of seal and/or pin). This will operate the davits such that the lifeboat or lifeboat encasement is repositioned into a position suitable for lowering the lifeboat to the surface of the sea, and

- through the hatch, operate a second valve via a second handle (possibly by initial removal of seal and/or pin). This initiates the descending sequence. Descending may be controlled by means of a reverse function of the hydraulic motor as per the present invention. Descend is configured so that the action is purely mechanical and performed by means of the force of gravity only.

The first and second handles may be interlocked such that it will not be possible to operate the second valve or handle prior to operating the first handle or valve.

The hydraulic control system may be configured such that the weight of the lifeboat does not influence the descending velocity of the lifeboat.

According to a further aspect of the present invention, leak oil from the hydraulic motor may be monitored or measured. The system may be configured for, on basis of the monitoring or measurement of the leak oil, determine a state of malfunction or over speed of the motor and as a result, activate the disc brake system.

The system may, in its entirety or not, be incorporated into an encasement such as the encasement disclosed in WO 09 153 240 A. The entire hydraulic system has to be able to cope with peak loads, such as sudden shocks created by start and stop operations etc. It has been found that by resiliently installing the encasement, including at least the winch of the system, at its place of application, scantlings of the hydraulic system may be significantly reduced as shocks etc. are absorbed be the resilient installation. The resilient installation may be obtained by interposing various forms of, in a combination or not, shock absorbing rubber, springs, Belleville washers and the like in-between the modular encasement and e.g. the deck of a ship,

The application and combination of features and solutions presented by the present invention is not limited to the presented embodiments. One or more features of one embodiment can and may be combined with one or more features of other embodiments, whereby not described but valid, embodiments of the present invention may be obtained.

The term "comprises/comprising/comprised of" when used in this specification incl. claims is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.