Fender
United States Patent 3918384
The present invention relates to a fender consisting of a carrier body and a pad made of plastic material whose surface presents a reduced coefficient of friction.
US Patent References:
Bumper means
Pollock - July 1957 - 2799494
Cushioning bumper for loading docks
Pfleger - January 1965 - 3165305
Bumpers
Miller - November 1967 - 3353812
RESIN FOAM-METAL LAMINATE COMPOSITES
Weber et al. - November 1969 - 3467569
METAL-CLAD LAMINATES
Pyle - January 1973 - 3711365
Bumper means
Pollock - July 1957 - 2799494
Cushioning bumper for loading docks
Pfleger - January 1965 - 3165305
Bumpers
Miller - November 1967 - 3353812
RESIN FOAM-METAL LAMINATE COMPOSITES
Weber et al. - November 1969 - 3467569
METAL-CLAD LAMINATES
Pyle - January 1973 - 3711365
Application Number:
05/392610
Publication Date:
11/11/1975
Filing Date:
08/20/1973
View Patent Images:
Export Citation:
Assignee:
Schlegel GmbH vormals Weill & Reineke
Primary Class:
Other Classes:
405/215
International Classes:
B63B59/02; E02B3/26; B63B59/00; E02B3/20; B63B59/02
Field of Search:
114/219 61/48 293/71 161/216 267/139-141
US Patent References:
| 3767521 | MULTI-PLY, METAL-CLAD SANDWICH PANELS | October 1973 | Glaser et al. |
Primary Examiner:
Blix, Trygve M.
Assistant Examiner:
Goldstein, Stuart M.
Attorney, Agent or Firm:
Cumpston & Shaw
Claims:
What we claim is
1. A fender comprising:
2. The fender of claim 1 wherein said plastics material of said pad consists of at least 95% of said polyolefins.
3. The fender of claim 1 wherein said plastics material of said pad comprises polyethylene.
4. The fender of claim 1 wherein said pad is bonded to said carrier body by fusion bonding.
5. The fender of claim 1 wherein said carrier body and said pad have corresponding projections and recesses that engage one another in form-locking fashion.
6. The fender of claim 1 wherein said pad is formed of a plurality of extruded layers bonded to one another by fusion, and the directions of extrusion of said layers are transverse to one another and extend generally parallel with said carrier body.
1. A fender comprising:
2. The fender of claim 1 wherein said plastics material of said pad consists of at least 95% of said polyolefins.
3. The fender of claim 1 wherein said plastics material of said pad comprises polyethylene.
4. The fender of claim 1 wherein said pad is bonded to said carrier body by fusion bonding.
5. The fender of claim 1 wherein said carrier body and said pad have corresponding projections and recesses that engage one another in form-locking fashion.
6. The fender of claim 1 wherein said pad is formed of a plurality of extruded layers bonded to one another by fusion, and the directions of extrusion of said layers are transverse to one another and extend generally parallel with said carrier body.
Description:
BACKGROUND
As the task of a fender is to attenuate the impact of ships by absorbing energy, layers of plastic material form an elastic pad in known fender means of this variety. Their carrier body merely serves to attach the elastic pad to a supporting structure, such as the wall of a pier, the body of a ship, a berth, the wall of a dock or the wall of a lock. In this case a reduced coefficient of friction shall ensure that the transfer of forces remains low in the direction parallel to the surface of the fender. As an example, German Pat. (provisional disclosure) No. 2,036,118 presents a pad in one piece and made of plastic, whose surface area is massive, whilst the under-lying material is plastic foam. British Pat. No. 1,120,308 presents a fender whose padded body made of elastic material is covered by a plate of relatively hard and smooth material.
It has been found, however, that fender means of this variety possess a resistance which is too low with respect to stress components directed in parallel to the fender surface. The bodies of vessels never being entirely even, these fender means are irregularly compressed by the impact of the surface of such vessels. In this case it can happen that a zone of high compression is adjacent to a zone of lower compression. If, under these circumstances, the movement of the ship runs in the direction inwhich the fender extends, and the zone of the highest compression thus wanders, excessive squeezing of the fender will occur, leading to an excessive stress in the direction of the extension of the fender, even in the case of fender materials whose coefficient of friction is low. This stress, in conjunction with the squeezing of the fender, is liable to lead to the rupture of the padding layer or to the destruction of the bond between the uppermost layer of the fender and the padding layer. In order to obviate this possibility, the padding layer as well as the bond between the two layers must be of high quality, thus these known fender means become very expensive.
SUMMARY OF THE INVENTION
The present invention is based on the problem of providing a fender consisting of a carrier body and of a pad having a smooth surface which presents a substantially higher resistance against forces acting in the direction of its extension.
According to the present invention the solution of this problem consists in the pad being essentially massive and rigidly attached to a rigid carrier body and constituted by polyolefins amounting to at least 80 per cent of its volume.
A massive layer of polyolefins practically shows no padding effect. Its elasticity is so small that it can actually be neglected. As the carrier body shall also be rigid, thus practically not receding or bending under the influence of the forces occurring during operation, the surface of the fender becomes inherently stable in essence. This has the result that rugosities of the body of a ship do not cause local compressions to the extent as it is the case with fenders having elastic surfaces. Therefore the stress components being directed in parallel to the surface of the fender can only be conveyed to a much lower extent. The fender made in accordance with the present invention is thus substantially more relieved of these forces than the known fender means. The zone comprising the bond between the pad and the rigid carrier body is not exposed to squeezing and thus presents essentially fewer problems than the known fender means. Stability requirements for the pad are also substantially reduced so that less qualified and cheaper material can be chosen.
If forces directed in parallel to the extension of the fender according to the present invention have essentially to be considered, as it is the case with locks or docks, a separate device serving to damp the impacts can be omitted. If, however, such a damping device is required, it can be placed between the rigid carrier body and the supporting structure, whereas, in the case of known fender means, this damping device has been foreseen between the surface of the fender exposed to friction and the carrier body. Therefore, in the case of the fender according to the present invention, potential impact damping devices do not jeopardize the rigidity of the surface exposed to friction. According to the present invention these damping devices can also be simplified, because the rigid carrier body disperses incident stress over the entirety of the damping devices situated behind the latter, and, consequently, locally occurring and concentrated peak deformations and peak forces do not have to be taken into account.
Polyolefins have been selected for the pad to be made of plastic material, because they present a coefficient of friction which is by far the lowest among comparatively cheap plastic materials.
U.S. Pat. No. 3,418,815 already presents a padding fender consisting of rubber or elastic material, in which a stiffening plate is embedded close to the surface exposed to friction, this plate being intended to distribute locally occurring peak forces and being bendable to a certain degree. As regards forces that are vertically incident upon the surface of the fender, this arrangement appears to be useful; however, it cannot prevent certain local compressions, as, on one hand, the plate remains bendable to a certain degree, and as on the other hand, the elastic material situated between the plate and the surface of the fender yields under the impact. As rubber and all elastic synthetic materials have a high coefficient of friction, rugosities of the ship can practically engage in the surface of the fender or can at least cause stress and squeezing that combine locally and that might lead to the destruction of the fender. As the fender is consequently only adapted to receive forces directed normally with respect to the extension of its surface, it cannot be deducted that the combination of a rigid carrier body with a nonelastic smooth olefin pad can lead to the results intended to be obtained in accordance with the present invention.
As stated above, this pad need not consist of polyolefins for up to 100 per cent of its volume. However, only such additives ought to be admitted that do not essentially increase the reduced coefficient of friction and the low elasticity of the pad made of synthetic material, but rather tend to further reduce these values. For instance, the material employed can contain glass fibres or other fibrous material, in order to reinforce the pad and to reduce its wear. The pad preferentially consists of more than 95 per cent of polyolefins, preferably polyethylene.
The hardness of the pad is advantageously of a value lying between Shore D 40 and Shore D 74, preferably in the vicinity of Shore C 60.
The pad made of plastic material is advantageously bonded to the carrier body over the entire surface or essentially over the surface. Bonding is preferably achieved by fusing. In order to improve the bond, both carrier body and pad can be provided with corresponding projections and recesses engaging in one another in form-locking fashion. Shock absorbing means can be provided on the face of the carrier body turned away from the pad and in a way that is known in itself.
As regards the ruggedness of the pad made of plastic material, it has been found useful to compose the latter of several layers having microstructures of different orientations. Therefore the pad consists of several layers obtained by extrusion and bonded to one another by fusion or welding, the layers being arranged in such a way that their directions of extrusion cross one another and extend in planes that are parallel to the carrier body.
According to the present invention a pad having a thickness of at least 5 cm and being arranged on a metallic carrier plate, is obtained by bonding a first or several first layers to the carrier body, which is at least brought to the fusing temperature of the plastic material, the subsequent layers being applied after the carrier body has cooled down. By this means close contact is first established between the lowermost layer of the pad and the carrier body, the applied layer of plastic material, however, not being so thick as to produce detrimental tensions after the carrier body has cooled down. Thus the first layer can be bonded more easily to the next layer of the pad. Then subsequent layers are applied after the carrier body has cooled down. In this case it suffices to adequately heat the surface turned away from the carrier body and belonging to the first layer. Preferably, all layers are applied onto the carrier body or the respective preceding layers, immediately after having been extruded and when still being ductile.
In this way it would be possible to form the pad merely out of two layers. Practical experience has proved, however, that it is more advantageous to arrange a multitude of relatively thin layers, one on top of the other. In this respect the layer previously defined as the first layer as well as the following layer can consist of a multitude of thin layers. In this context it is possible that the cooling of the carrier body is performed step by step while applying the various layers of plastic material. The differing orientations of the microstructure of the various layers can be obtained by applying layers under varying directions of the extrusion.
When practically performing the procedure according to the present invention by using a fabricating device, e.g. an extrusion device having a flat nozzle, a strip of say 10 mm by 100 mm is extruded. By applying radiated heat that is intended to compensate for heat losses in the strip of plastic after having left the nozzle, this strip is pressed onto the surface of a steel plate serving as the carrier body and brought to the same temperature as the strip, which is deposited on this steel plate along the longer side of its cross section. In this case, the extruding device is advantageously placed vertically above the steel plate to be covered, and if this steel plate is of rectangular shape, the extruding device is conveniently moved from one side of the steel plate to the other, the strip of plastic being entirely deposited on the surface of the steel plate and pressed onto the latter. After having deposited one strip the extruding device will apply another strip in parallel and adjacent to the first strip. In principle it is of no importance if the extruding device is moved with respect to the steel plate, or if -- vice versa -- the steel plate is moved with respect to the extruding device.
After the first layer of strips has been completed, the next layer can be applied. For reasons of stability it is advantageous, but not absolutely necessary, to apply this next layer at right angles with respect to the direction of the strips of the preceding layer. In order to bond the layers to one another, the surface of the layer that has already been deposited is first and by means of heat radiating devices brought to a temperature that allows an entirely homogenious fusion (welding) with the strips of the following layer. The subsequent layers of strips should also be applied at right angles with respect to the preceding layers. This yields the most favourable conditions as regards the distribution of mechanical tensions over the steel plate when the fender has cooled down. As indicated before, the varying directions of the subsequent layers of strips are not absolutely required, and this holds true in particular, if a favourable transfer of forces is ensured from the pad towards the steel plate by means of large recesses in the surface of the steel plate, this, however does not depend on the bonding effect of the pad placed on the steel plate. The resistance against the influence of weather conditions is also favourably changed by such a form-locking bond.
Due to the volume shrinkage occurring in the case of the plastic material, attention has to be paid to the fact that the first layers are deposited up to a thickness not exceeding 3 cm. Afterwards complete cooling to room temperature is possible, without degrading effects on further layers subsequently deposited on the preceding layers that are heated merely superficially. Particularly for fender plates that are exposed to high stresses and strains the layers can be reinforced by introducing adequate reinforcing textures consisting of glass fibres between the individual layers, in order to transfer stresses and strains into the plate.
DRAWINGS
A preferred embodiment of the fender in accordance with the present invention is described hereinafter by way of example and with reference to the attached drawings, of which
FIG. 1 represents a side sectional view taken across the fender in accordance with the present invention, and
FIG. 2 shows another side sectional view taken through the fender along its extension and transverse to the section of FIG. 1.
DETAILED DESCRIPTION
The carrier body consists of a steel plate 1, which is 4 m long and 1 m wide and has several recesses 2 of square cross-sectional shape measuring approximately 8 cm by 8 cm and being stiffened on its lower surface by means of a rib 3 (evidently, it is also possible to provide several ribs).
The entire surface of the steel plate 1 is covered by a pad 4 made of plastic material and also completely filling the recesses 2 and being bonded to the carrier body in these recesses 2 in form-locking fashion. The thickness of the pad 4 lies between five and twelve centimeters, for instance being 8 cm. The carrier body is conveniently attached to the pier or berth, e.g. by employing bores 5 situated in the rib 3 with elastic shock absorbing members being interposed. A plurality of such fender plates can be grouped into one larger unit of plates.
The pad 4 is worn off with time and can be renewed without difficulty. The procedure in accordance with the present invention easily permits application of new layers of strips on the existing remainders of the pad 4 or immediately on the carrier body, which is rendered free of the latter. As the procedure is not bound to a well defined shape of the carrier body, deformed carrier bodies can also be provided with new pads 4 without any difficulty.
It is evident that the recesses foreseen in the surface of the carrier body can be provided in other shapes and quantities.
The fender manufactured in accordance with the present invention does not only present a more advantageous performance, but it can also be produced and repaired very economically.
The individual layers 4a to 4d constituting the pad 4 are indicated by dashed lines in FIG. 2.
As the task of a fender is to attenuate the impact of ships by absorbing energy, layers of plastic material form an elastic pad in known fender means of this variety. Their carrier body merely serves to attach the elastic pad to a supporting structure, such as the wall of a pier, the body of a ship, a berth, the wall of a dock or the wall of a lock. In this case a reduced coefficient of friction shall ensure that the transfer of forces remains low in the direction parallel to the surface of the fender. As an example, German Pat. (provisional disclosure) No. 2,036,118 presents a pad in one piece and made of plastic, whose surface area is massive, whilst the under-lying material is plastic foam. British Pat. No. 1,120,308 presents a fender whose padded body made of elastic material is covered by a plate of relatively hard and smooth material.
It has been found, however, that fender means of this variety possess a resistance which is too low with respect to stress components directed in parallel to the fender surface. The bodies of vessels never being entirely even, these fender means are irregularly compressed by the impact of the surface of such vessels. In this case it can happen that a zone of high compression is adjacent to a zone of lower compression. If, under these circumstances, the movement of the ship runs in the direction inwhich the fender extends, and the zone of the highest compression thus wanders, excessive squeezing of the fender will occur, leading to an excessive stress in the direction of the extension of the fender, even in the case of fender materials whose coefficient of friction is low. This stress, in conjunction with the squeezing of the fender, is liable to lead to the rupture of the padding layer or to the destruction of the bond between the uppermost layer of the fender and the padding layer. In order to obviate this possibility, the padding layer as well as the bond between the two layers must be of high quality, thus these known fender means become very expensive.
SUMMARY OF THE INVENTION
The present invention is based on the problem of providing a fender consisting of a carrier body and of a pad having a smooth surface which presents a substantially higher resistance against forces acting in the direction of its extension.
According to the present invention the solution of this problem consists in the pad being essentially massive and rigidly attached to a rigid carrier body and constituted by polyolefins amounting to at least 80 per cent of its volume.
A massive layer of polyolefins practically shows no padding effect. Its elasticity is so small that it can actually be neglected. As the carrier body shall also be rigid, thus practically not receding or bending under the influence of the forces occurring during operation, the surface of the fender becomes inherently stable in essence. This has the result that rugosities of the body of a ship do not cause local compressions to the extent as it is the case with fenders having elastic surfaces. Therefore the stress components being directed in parallel to the surface of the fender can only be conveyed to a much lower extent. The fender made in accordance with the present invention is thus substantially more relieved of these forces than the known fender means. The zone comprising the bond between the pad and the rigid carrier body is not exposed to squeezing and thus presents essentially fewer problems than the known fender means. Stability requirements for the pad are also substantially reduced so that less qualified and cheaper material can be chosen.
If forces directed in parallel to the extension of the fender according to the present invention have essentially to be considered, as it is the case with locks or docks, a separate device serving to damp the impacts can be omitted. If, however, such a damping device is required, it can be placed between the rigid carrier body and the supporting structure, whereas, in the case of known fender means, this damping device has been foreseen between the surface of the fender exposed to friction and the carrier body. Therefore, in the case of the fender according to the present invention, potential impact damping devices do not jeopardize the rigidity of the surface exposed to friction. According to the present invention these damping devices can also be simplified, because the rigid carrier body disperses incident stress over the entirety of the damping devices situated behind the latter, and, consequently, locally occurring and concentrated peak deformations and peak forces do not have to be taken into account.
Polyolefins have been selected for the pad to be made of plastic material, because they present a coefficient of friction which is by far the lowest among comparatively cheap plastic materials.
U.S. Pat. No. 3,418,815 already presents a padding fender consisting of rubber or elastic material, in which a stiffening plate is embedded close to the surface exposed to friction, this plate being intended to distribute locally occurring peak forces and being bendable to a certain degree. As regards forces that are vertically incident upon the surface of the fender, this arrangement appears to be useful; however, it cannot prevent certain local compressions, as, on one hand, the plate remains bendable to a certain degree, and as on the other hand, the elastic material situated between the plate and the surface of the fender yields under the impact. As rubber and all elastic synthetic materials have a high coefficient of friction, rugosities of the ship can practically engage in the surface of the fender or can at least cause stress and squeezing that combine locally and that might lead to the destruction of the fender. As the fender is consequently only adapted to receive forces directed normally with respect to the extension of its surface, it cannot be deducted that the combination of a rigid carrier body with a nonelastic smooth olefin pad can lead to the results intended to be obtained in accordance with the present invention.
As stated above, this pad need not consist of polyolefins for up to 100 per cent of its volume. However, only such additives ought to be admitted that do not essentially increase the reduced coefficient of friction and the low elasticity of the pad made of synthetic material, but rather tend to further reduce these values. For instance, the material employed can contain glass fibres or other fibrous material, in order to reinforce the pad and to reduce its wear. The pad preferentially consists of more than 95 per cent of polyolefins, preferably polyethylene.
The hardness of the pad is advantageously of a value lying between Shore D 40 and Shore D 74, preferably in the vicinity of Shore C 60.
The pad made of plastic material is advantageously bonded to the carrier body over the entire surface or essentially over the surface. Bonding is preferably achieved by fusing. In order to improve the bond, both carrier body and pad can be provided with corresponding projections and recesses engaging in one another in form-locking fashion. Shock absorbing means can be provided on the face of the carrier body turned away from the pad and in a way that is known in itself.
As regards the ruggedness of the pad made of plastic material, it has been found useful to compose the latter of several layers having microstructures of different orientations. Therefore the pad consists of several layers obtained by extrusion and bonded to one another by fusion or welding, the layers being arranged in such a way that their directions of extrusion cross one another and extend in planes that are parallel to the carrier body.
According to the present invention a pad having a thickness of at least 5 cm and being arranged on a metallic carrier plate, is obtained by bonding a first or several first layers to the carrier body, which is at least brought to the fusing temperature of the plastic material, the subsequent layers being applied after the carrier body has cooled down. By this means close contact is first established between the lowermost layer of the pad and the carrier body, the applied layer of plastic material, however, not being so thick as to produce detrimental tensions after the carrier body has cooled down. Thus the first layer can be bonded more easily to the next layer of the pad. Then subsequent layers are applied after the carrier body has cooled down. In this case it suffices to adequately heat the surface turned away from the carrier body and belonging to the first layer. Preferably, all layers are applied onto the carrier body or the respective preceding layers, immediately after having been extruded and when still being ductile.
In this way it would be possible to form the pad merely out of two layers. Practical experience has proved, however, that it is more advantageous to arrange a multitude of relatively thin layers, one on top of the other. In this respect the layer previously defined as the first layer as well as the following layer can consist of a multitude of thin layers. In this context it is possible that the cooling of the carrier body is performed step by step while applying the various layers of plastic material. The differing orientations of the microstructure of the various layers can be obtained by applying layers under varying directions of the extrusion.
When practically performing the procedure according to the present invention by using a fabricating device, e.g. an extrusion device having a flat nozzle, a strip of say 10 mm by 100 mm is extruded. By applying radiated heat that is intended to compensate for heat losses in the strip of plastic after having left the nozzle, this strip is pressed onto the surface of a steel plate serving as the carrier body and brought to the same temperature as the strip, which is deposited on this steel plate along the longer side of its cross section. In this case, the extruding device is advantageously placed vertically above the steel plate to be covered, and if this steel plate is of rectangular shape, the extruding device is conveniently moved from one side of the steel plate to the other, the strip of plastic being entirely deposited on the surface of the steel plate and pressed onto the latter. After having deposited one strip the extruding device will apply another strip in parallel and adjacent to the first strip. In principle it is of no importance if the extruding device is moved with respect to the steel plate, or if -- vice versa -- the steel plate is moved with respect to the extruding device.
After the first layer of strips has been completed, the next layer can be applied. For reasons of stability it is advantageous, but not absolutely necessary, to apply this next layer at right angles with respect to the direction of the strips of the preceding layer. In order to bond the layers to one another, the surface of the layer that has already been deposited is first and by means of heat radiating devices brought to a temperature that allows an entirely homogenious fusion (welding) with the strips of the following layer. The subsequent layers of strips should also be applied at right angles with respect to the preceding layers. This yields the most favourable conditions as regards the distribution of mechanical tensions over the steel plate when the fender has cooled down. As indicated before, the varying directions of the subsequent layers of strips are not absolutely required, and this holds true in particular, if a favourable transfer of forces is ensured from the pad towards the steel plate by means of large recesses in the surface of the steel plate, this, however does not depend on the bonding effect of the pad placed on the steel plate. The resistance against the influence of weather conditions is also favourably changed by such a form-locking bond.
Due to the volume shrinkage occurring in the case of the plastic material, attention has to be paid to the fact that the first layers are deposited up to a thickness not exceeding 3 cm. Afterwards complete cooling to room temperature is possible, without degrading effects on further layers subsequently deposited on the preceding layers that are heated merely superficially. Particularly for fender plates that are exposed to high stresses and strains the layers can be reinforced by introducing adequate reinforcing textures consisting of glass fibres between the individual layers, in order to transfer stresses and strains into the plate.
DRAWINGS
A preferred embodiment of the fender in accordance with the present invention is described hereinafter by way of example and with reference to the attached drawings, of which
FIG. 1 represents a side sectional view taken across the fender in accordance with the present invention, and
FIG. 2 shows another side sectional view taken through the fender along its extension and transverse to the section of FIG. 1.
DETAILED DESCRIPTION
The carrier body consists of a steel plate 1, which is 4 m long and 1 m wide and has several recesses 2 of square cross-sectional shape measuring approximately 8 cm by 8 cm and being stiffened on its lower surface by means of a rib 3 (evidently, it is also possible to provide several ribs).
The entire surface of the steel plate 1 is covered by a pad 4 made of plastic material and also completely filling the recesses 2 and being bonded to the carrier body in these recesses 2 in form-locking fashion. The thickness of the pad 4 lies between five and twelve centimeters, for instance being 8 cm. The carrier body is conveniently attached to the pier or berth, e.g. by employing bores 5 situated in the rib 3 with elastic shock absorbing members being interposed. A plurality of such fender plates can be grouped into one larger unit of plates.
The pad 4 is worn off with time and can be renewed without difficulty. The procedure in accordance with the present invention easily permits application of new layers of strips on the existing remainders of the pad 4 or immediately on the carrier body, which is rendered free of the latter. As the procedure is not bound to a well defined shape of the carrier body, deformed carrier bodies can also be provided with new pads 4 without any difficulty.
It is evident that the recesses foreseen in the surface of the carrier body can be provided in other shapes and quantities.
The fender manufactured in accordance with the present invention does not only present a more advantageous performance, but it can also be produced and repaired very economically.
The individual layers 4a to 4d constituting the pad 4 are indicated by dashed lines in FIG. 2.