Patent Application
20090064918
The invention relates to an arrangement for manually releasing nautical life saving equipment, e.g. containers for inflatable life boats or rafts.
All major ships today are equipped with life boats or other similar equipment which shall function as rescue crafts in case of an emergency. These rescue crafts are usually provided with some arrangement in order to automatically release the life saving craft in case of an emergency. The automatic release mechanism can be triggered by sensing a pressure change of the environment so as to release the nautical life saving equipment when being subjected to a higher pressure, e.g. the pressure of water at a certain depth. In case of inflatable rafts, the inflating of the raft is triggered simultaneously or shortly after the release of the raft. Hence, in case of a shipwreck, the released raft will be inflated and move towards the surface in order to function as a life saving craft.
Even though the life rescuing equipment is provided with an automatic release mechanism, there is also a need for equipping the life rafts or life boats with a manual release mechanism. There are occasions when it is desired to be able to release the life raft at ones own will. This might be the case in the scenario of having a fire or conflagration as well as if the ship runs aground. Even in case of shipwreck, the use of the automatic release system is generally considered to be a back up for the manual release. Usually it is preferred to manually release the life saving equipment in order to be in a safe position as soon as possible. The purpose of the automatic release is to assure the life saving equipment will be available in case there is no time for manual release. Hence, it is important at these occasions to be able to quick and easy release the life raft or life boat. Referring to inflatable rafts or life boats, these are commonly kept in containers. Such containers are, while being fastened to suitable support stands on board the relevant ships, by means of claspable straps or the like, releasable retained on the support stands while having one of the ends of the straps permanently fastened onto the support stands and having the other ends of the straps releasable fastened to the support stands in a generally standardized manner involving a so-called “release hook” or “slip hook” being hooked into a hole within the support stand. It is common practice to place a hydrostatic automatic release arrangement between the manual release arrangement, e.g. a slip hook, and the end of the strap permanently fastened to the support or deck.
The release hook comprises an eye portion adapted to stay in connection with a back-bend end of the straps and a protruding base portion of the hook with a free end portion extending relatively far backwards which at the end comprises a retaining protrusion for the retaining of an anchoring ring encircled the base portion of the hook and the respective free end portion. The free hook end portion can be let through the retaining hole within the support stand and thereafter be locked against pull-out by letting the locking ring down over the retaining protrusion on the free end of the hook. The backwards protruding free end is resiliently depressible into the base portion of the hook so that, to manually achieve a release of the connection provided by the hook, the hook can be sufficiently compressed to release the locking ring from the retaining protrusion and thereafter flip and retract the hook from its grip in the hole in the support stand, thus releasing the floatable container
However, it has been found that the traditionally provided release hooks present problems of safety with regard to the easiness of release which is being required of them. Thus, when applying an initially tight tensioned strap, in case of exposure of the strap to an increased level of humidity, the tension of the strap is further augmented, and in that case a correspondingly strong tension within the strap provides a pulling in the release hook whereby the free end portion of the release hook is forced to an elastic pivoting away from the main stem of the hook thus resulting in a so strongly augmented outwards tensioning within the aforementioned locking ring that it becomes difficult to release it through a manual squeezing of the release hook. Furthermore, the release hook has to be released from the retaining gripping by being bent outwards to achieve a transverse translation of the external hook portion away from the retaining hole, and this necessary bending outwards of the hook is made difficult to perform due to an increased pulling within the eye-end of the hook. This arrangement indicates there is a need for another fastening system, in which a fairly easy provided releasing is safeguarded which is independent on the size of the tension within the strap. In addition, the manual release mechanism should be resistant to the rather rough environment to which it is exposed and shall not be unable to release due to corrosion or other impact from the environment, e.g. it should preferably not be harmfully affected by low temperature and icing of its components.
In EP 1 193 172 there is suggested an arrangement for manual release of nautical life saving equipments. In the background art discussion in EP 1 193 172, the problem of manually releasing the life raft when there are strong tension forces in the holding straps is mentioned. However, tests performed on the arrangement described in EP 1 193 172 have shown that a still better performance concerning the release force at heavy loads and strong tensions is desired. Furthermore, the system described in EP 1 193 172 includes a rather complicated arrangement including several details needed to be put together. In addition, the arrangement seems to be inferior to the slip hook arrangement concerning reclosing of the arrangement if there is a need to release and reclose the arrangement for test purposes. EP 1 193 172 is also silent about how it will work in case of tough and corrosive environment as well as how it will work when subjected to cold weather and icing.
Hence, there is a need for an improved release arrangement for manually releasing life saving equipment, e.g. a container of an inflatable raft, in order to achieve a safe and quick release of the equipment.
The present invention aims to provide a release system for nautical life saving equipment, e.g. containers for inflatable life boats or rafts in order to overcome the above mentioned deficiencies in prior art solutions.
In one embodiment of the present invention, a manual release arrangement for releasing nautical life saving equipment, e.g. containers for inflatable life rafts, is located as a connecting link between a first rope arrangement and a second rope arrangement adapted to fixating the life saving equipment. The second rope arrangement forms a loop encircling the first rope arrangement. The first rope arrangement is fixed to a connecting stick so that the connecting stick together with the first rope arrangement forms a stop preventing the loop of the second rope arrangement to run along the first rope arrangement. The connecting stick is adapted, at release, to turn around an axis formed by the loop of the second rope arrangement. The axis is orthogonal to the longitudinal axis of the rope arrangements.
Hence, the connecting stick will engage the two rope arrangements when there is a force applied to the ropes, striving in opposite directions, in order to separate the ropes.
In the following examples, the connecting stick comprises a front panel connected to two side panels extending essentially perpendicular to said front panel from the under side of said front panel along at least a part of the longitudinal axis of the connecting stick. The construction may also be solid but due to saving of material it is preferred to use this construction. Whether the construction is made of sheet material, e.g. bent sheet metal, or made of solid material, it is constructed so that the momentum of the turning force from the second rope arrangement is small due to the short lever arm effected by the second rope arrangement around the axis formed by the first rope arrangement while the relatively low friction forces of the second rope arrangement against the sides of the connecting stick have a longer lever arm. This arrangement will make the connecting stick to be locked in a position near the equilibrium point of the applied forces.
The stabilized position of the connecting stick is depending on the fact that the second rope arrangement is working, with its forces in opposite turning directions, so as to neutralise each other. In addition to this stabilising arrangement, there are also friction forces from the rope arrangements, mainly the second rope arrangement, working on the stick, which forces contribute to the maintaining of the connecting stick in its locking position. Hence, the resultant of the turning force must be balanced and lower than the resulting friction force in order to make the connecting stick work.
The applied force is relatively independent on the dimensions of the rope arrangements. However, it is believed that the design of the stick, for example the width and shape of the front panel as well as the angle between the front panel and the side panels influences the forces and their possibility to work on the stick. For example, if the stick would be a plain, round rod, without any protrusions or indentations, there would hardly be any forces working to restrict such a connecting stick from turning by itself and release. The forces working at the very point of the loop of the second rope arrangement would overrule the forces working in the opposite direction and the connecting stick would turn and release if not provided with a locking arrangement as described below. However, a stick having an oval shape might work, provided that the stick would be wide and flat enough to provide enough grips for the opposite turning forces to balance the turning force working at the very point of the loop.
The connecting stick may further be provided with a locking arrangement which is adapted to prevent the connecting stick to release unintentionally. In one embodiment, the locking arrangement comprises a locking pin which is fitted into holes placed in each one of the side panels, or if the construction is a solid piece in a hole extending through the piece, so as to extend essentially perpendicular to the longitudinal axis of the connecting stick. The locking pin will restrict the connecting stick to turn due to the interaction with the parts of the second rope arrangement located on each side of the connecting pin while forming a sling.
The front panel of the connecting stick may further be provided with a hole adapted to receive the first rope arrangement in order to fix the first rope arrangement to the connecting stick. In one embodiment the under side of front panel is provided with a holding stick in the hole. The stick is placed so that a rope arrangement may be inserted through the hole from the upper side of the connecting stick, at one side of the hole, and encircling the holding stick in order to be inserted in the hole once again, entering from the under side of the connecting stick at the other side of the hole, so as to fix the rope arrangement to the connecting stick. In another embodiment it is possible to provide the connecting stick with two holes whereby the rope arrangement enter one hole from the upper side of the connecting stick and continue to enter the other hole from the under side so as to form a loop round the connecting stick and thereby fixing the rope arrangement to the connecting pin.
The expression “rope arrangement” is used herein. The expression is to be interpreted to comprise such means as ropes, wires, straps, chains, one or more pivotally connected small bars or the like which essentially have the same function or could work as a rope. The expression also includes the use of several ropes or the like in order to function as a rope. Such a rope arrangement may contain parts of different material combined.
The “rope arrangement” may further be provided with a cover material or treated on its surface at positions which are subjected to severe wearing. These positions of the rope arrangements may for example be the parts forming the loops or the parts nearby which are in contact with each other and the connecting pin when forming the locking arrangement. The part of the second rope arrangement forming the turning axis may be formed of stiffer material.
In the following part, certain dimensions and designs of the ropes and parts forming the release arrangements have been used. These specific embodiments only serve as examples of the present invention. It is obvious for the skilled person in the art that he may use the ideas as described in the present claims or description in order to construct new embodiments within the inventive idea of this invention. For example may the form and size of the hole, where the first rope arrangement is located, be varied, as well as its location on the connecting stick. In one embodiment there may be two separate holes instead of one. The location of the hole may be tried out so as to provide a position where the arrangement is near the equilibrium in order to achieve the desired release force.
In the following examples, the release stick is made from bent sheet metal to form a front panel and side panels. It is obvious that the stick may be formed in other ways, e.g. it may be formed as a solid stick having an upper side and two sides of the same contour as described in the examples or having other shapes. The material used may be any material suitable to resist the rough environment from salt water and large temperature changes.
b The first embodiment of the manual release arrangement according to the present invention together with an automatic release arrangement
In
The slip hook 107 might be released by pivotally pressing the fork branch 109 towards the stem 111 so that the distal part of the branch is getting close enough to the stem 111 and the locking ring 112 may be threaded over the distal end of the fork branch. This part is connected to a part of an automatic, hydrostatic release coupling device 114 which moreover is coupled onto a fixed bottom part of the support stand 104 via a lower strap 115. The release arrangement of the strap 105 may thus work as well manually as automatically. By releasing the fork branch 109 from the locking ring 112, by pushing the fork branch 111 towards the stem while guiding the ring 112 over the protrusion 110 of the distal end of the fork portion, and thereby releasing the fork portion to freely rotate at its base, the slip hook 107 will be released from its engagement with the retaining hole 113 so as to disengage from its locking position.
Even though this arrangement in many ways have been reliable in connecting the straps or wires with a support or the deck, it has turned out that the force to manually release the container may be too high. An essential feature of a release arrangement for life saving equipment on board a ship is the easiness to trigger the release. An increase of the force from the strap, e.g. due to shrinking of the strap or a list of the ship, will result in an increased tension in the slip hook. The distal end of the fork portion will be pivoting away from the stem with a force proportional to the increased force of the strap and render difficult the release of the slip hook. The use of a slip hook has a further disadvantage in that it often requires two operations to be performed simultaneously to release the locking, the pressing together of the stem and the fork portion of the slip hook while at the same time move the locking ring along the fork portion to pass the protrusion of the distal end and disengage the bounding of the fork portion. The slip hook is also inferior compared to the release arrangement according to the present invention in respect of icing. When the slip hook is iced, the release might become much more difficult due to the need of stronger force in order to break the ice. The slippery surface will also make it harder to get a grip of the release hook and make the rather finicky job to release the hook even harder.
In
In order to release the arrangement, the connecting stick 207 is turned around a axis, said axis being parallel to the X-axis and formed by the loop 213 of the second rope 215 (referring to
In order to test the invention, 3 series using different setups of the rope arrangement was tested. In the first test series only ropes were used while in the second series combinations of wires and ropes for the different slings were used and in the third series only wires were used. The forces applied to the connecting stick by means of the rope arrangements were varied and tests were made to measure the force needed to release the manual release arrangement.
In
The proportions, scale and design of the connecting stick 307 corresponds to the stick used in the tests. Hence, the stick is drawn in scale 1:1. In
However, the tested connecting pin 307 illustrated in
In
In
In
In
The tests have shown that this arrangement have certain benefits concerning the easiness of releasing. The test results below indicates that the force needed to release the arrangement not is proportional to the forces effected by the straining of the ropes but remain rather constant. The tests of the manual release arrangement was performed using different rope arrangements, i.e. different material (traditional ropes and wires) and different dimensions, i.e. changing the diameter of the rope arrangements used for the slings. The results are as follows:
In the tests performed, the force required to trigger the connecting stick to release was somewhat proportional to the tension force in the lower region, i.e. below an applied force of approximately 1000 N, and the needed release force to trigger the turn of the connecting stick was below 100 N. When the release arrangement was subjected to stronger tension forces, i.e. from 1000 to 15000 N, the needed release force to trigger the turn of the connecting stick was stabilized between 100 N and 200 N. In none of the cases was the required force to turn the connecting stick greater than 200 N. This phenomenon is at least partly caused by the connection between the increased friction forces between the sides of the connecting stick and the adjacent rope (see
A further explanation to the phenomenon beyond this result is the positioning of the connecting stick in an unstable position of equilibrium. Even though the connecting stick will remain in its locking position when not subjected to any additional turning force, the equilibrium is unstable which in turn results in that a minor force will be enough to disturb the balance so that the connecting stick will rotate to release the arrangement. It is further obvious from the construction that the stick is only able to rotate in the releasing direction since it is hindered by the axis, formed by the loop of the first rope, to rotate to be even more secured. Hence, there is no risk the arrangement will rotate so as to end up in a stable locking position unable to release.
In the experimental studies there were no detailed protocols over the exact values of the release force needed to pull the release arm 318 and make the locked rope to loosen up. There were no significant systematical difference in the needed force between the different size (diameters) of the ropes and wires. This is partly due to due to inaccuracy in the measuring equipment but also to the rather many parameters influenced by the change of the rope arrangement and applied force, e.g. the diameter of the rope forming the first sling influences the thickness of the axis around which the connecting stick turns when releasing, the friction forces due to different material in the rope arrangement and its interconnection with the release stick will also have an impact on the resulting release force.
In a further test, the release arrangement was tested concerning its functionality when subjected to cold weather and icing of the parts. In this test, the manual release arrangement 206 was placed near an automatic release arrangement 214 as shown in
There are some adjustments which can be made to the release stick in order to facilitate release of the connecting stick. In
There are of course other ways to influence the releasing force to turn the connecting stick from a locked position to a releasing position. For example, the surface of the side panels (shown in
In the shown embodiments, the connecting stick is provided with a security locking pin which has to be removed in order to be able to turn the stick and release the connecting stick. The release arrangement will work even if there is no such locking pin present since the locking pin is only intended to avoid unintentional release if someone accidentally is turning the release arm. In the shown embodiments the locking pin is exemplified as shown in
In another embodiment of the present invention, the first rope arrangement may be fixed to the connecting stick in some other way. In case a thick rope is used in the first rope arrangement it may be fastened in the hole in the connecting pin by threading it through the hole and tie a knot on the opposite side in order to fix the rope at the connecting stick. Hence, even if a preferred embodiment of how to fix the first rope arrangement to the connecting stick is taught in the examples it is obvious for the skilled person in the art that there are several ways of fixing this rope to the connecting pin which are within the inventive idea of the invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/SE2005/000633 | 5/2/2005 | WO | 00 | 10/29/2007 |
