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(11) | EP 0 318 264 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Travelling container crane |
| (57) A travelling container crane comprises a mobile gantry (10) mounted for sideways
movement on fixed ground rails (14) and two parallel spaced-apart beams (16, 17) supported
by and extending horizontally from the gantry (10) in a direction perpendicular to
the direction of motion of the gantry. A respective mobile trolley (22, 23) is supported
under each beam on rails fixed to the beam for to-and-fro movement of the trolley
along the beam on the beam rails, and a respective hoistable container-lifting device
(33) is suspended from each trolley. In the preferred embodiment, a third mobile trolley
(30) and associated container-lifting device (33) is supported between the two beams
on further rails fixed to the two beams, whereby the third trolley may move to and
fro along the space between the beams on the said further rails. |
[0002] The storing of freight cargo in steel containers for the purpose of transportation by sea or land is a relatively recent practice, dating from the 1950s, and such cargo containers have a range of standard dimensions to permit ready transfer between ships, trucks, railway wagons, etc.
[0003] The width of such containers has been standardisesd at 8 or 8.5 feet, and their height is generally 8 feet also, although some 4 foot "half-height" containers are used and sometimes the height may be 9 or 9.5 feet. The great majority of cargo containers used in international trade have a length of either 20 feet or 40 feet, although there are small numbers of containers with lengths of 35, 45 and 48 feet.
[0004] In order to lift such cargo containers to and from, for example ships, railway wagons and trucks, a special type of crane, known as a travelling container crane, has been developed. This is a type of crane comprising a mobile gantry mounted for sideways movement on rails fixed in or to the ground, a beam supported by and extending horizontally from the gantry in a direction perpendicular to the direction of motion of the gantry, a mobile trolley supported under the beam on rails fixed to the beam for to-and-fro movement of the trolley along the beam on the beam rails, and a hoistable container-lifting device ("spreader") suspended from the trolley. The hoist itself may be mounted on the trolley or located in a machinery house carried on the rearward portion of the beam.
[0005] Although not limited thereto, the present invention is especially concerned with ship-to-shore or quayside cranes, of the type where the gantry is of generally arched configuration having two front and two rear legs respectively which travel on the fixed ground rails, and where the beam extends at least under the front (or seaward side) of the arch, i.e. between the tops of the front two legs, and usually also projects beyond the rear (or landward side) of the arch, i.e. from between the rear two legs.
[0006] In such ship-to-shore cranes the portion of the beam forwardly of the arch (i.e. the portion which extends out over the edge of the quayside) is a derrick boom which can be raised from its horizontal position to provide clearance to allow the docking of ships to be unloaded and vice versa.
[0007] Most specialised container ships are designated LO-LO (lift-on, lift-off) vessels to distinguish them from roll-on, roll-off vessels. It is with the former that travelling quayside container cranes are used, the latter being loaded and unloaded with, for example, fork-lift trucks.
[0008] On LO-LO vessels the cargo containers are almost always stowed with their longitudinal axes parallel to the axis of the vessel, so that when the vessel is docked the container axes are parallel to the side of the quay. The quayside travelling crane is arranged for sideways motion along the quayside, i.e. parallel to the axes of the containers in the vessel, so that the beam extends out over the cargo hold in which the containers are stowed in a direction perpendicular to the container axes.
[0009] The containers are usually stowed in the vessel in such a manner that containers of the same length (usually 20 foot or 40 foot long) are located in alignment side-by-side in adjacent rows across the width of the ship, i.e. perpendicular to their own axes and to the axis of the ship, so forming a rectangular matrix or "layer" of containers, there being a number of such layers superimposed upon one another.
[0010] To unload a ship so loaded with containers, the quayside crane is moved to a position with its beam located centrally over one of the rows of containers, the trolley is moved to a position directly over a container to be unloaded, and the container hoist is lowered for fixing to the container by means of the spreader.
[0011] Then the container is lifted clear of the other containers and any other obstructions, and the trolley is moved rearwardly along the beam rails until it is directly over, for example, a truck or railway wagon located on the quay (usually within the area of the gantry between the quayside rails).
[0012] Finally the container is lowered onto the receiving vehicle and the spreader disconnected. The trolley is normally controlled by an operator situated in a cabin attached to the rear of the trolley for good visibility of the cargo container at all times.
[0013] Without moving the gantry, (except for minor adjustments required to engage the container) this procedure is repeated for all of the containers in the particular row aligned with the beam of the crane. Adjacent rows are then unloaded by moving the gantry until the beam is centrally located over the desired row, and the containers removed one-by-one for each row as described above. Successive "layers" of containers are similarly unloaded. Clearly, the procedure for loading a vessel is the reverse of the above.
[0014] The existing method of loading/unloading ships as described above suffers from a number of limitations.
[0015] In order to pass the maximum length of container through the front legs of the crane's gantry, these have to be spaced about 55 feet apart (48 foot container plus 3.5 feet clearance at each end). In addition to this 55 foot space, the gantry structure itself occupies further space on each side of the centre space.
[0016] Further, as is well known, the gantry legs usually run on the ground rails be means of a system of rocker beams, wheel bogies and wheels, the rocker beams ensuring an equal distribution of the cumulative vertical loading of the crane between the various wheels. A typical large container crane has 8 wheels per leg, and it is the distance apart of the outermost ends of the rocker beams and bogies which determines the overall width of the gantry.
[0017] Despite crane manufacturers' attempts to keep the overall crane width to a minimum so that two or more cranes standing side-by-side can approach as closely as possible to each other in order to "work" the ship more intensively, practical constraints such as leg spacing as referred to above and crane stability mean that in practice the closest that two cranes can get is about 80 feet as measured from the centre lines of the beams of each crane.
[0018] Accordingly, two side-by-side cranes can only work every fourth row of 20 foot containers or every second row of 40 foot containers at the same time.
[0019] It is therefore an object of the present invention to provide a construction of travelling container crane which can provide more intensive working of cargo containers arranged in layered matrix fashion as described above, whether on a vessel or elsewhere, for example in a freight storage depot.
[0020] Accordingly, the present invention provides a travelling container crane of the kind comprising a mobile gantry mounted for sideways movement on fixed ground rails, a beam supported by and extending horizontally from the gantry in a direction perpendicular to the direction of motion of the gantry, a mobile trolley supported under the beam on rails fixed to the beam for to-and-fro movement of the trolley along the beam on the beam rails, and a hoistable container-lifting device suspended from the trolley, wherein at least two parallel beams are provided supported in spaced apart side-by-side relationship by the gantry, each beam having a respective mobile trolley and associated hoistable container-lifting device.
[0021] The advantage of the invention is that by providing two beams on a common gantry, these can be located closer together than two beams on the gantries of two separate cranes, so that with suitable beam spacing alternate rows of 20 foot containers and adjacent rows of 40 foot containers can be worked simultaneously by a single crane.
[0022] Although such a crane would be wider than a normal single beam crane, it would nevertheless be narrower than two separate single beam cranes side-by-side, and this provides the possibility that a second such crane can be brought up to the first crane, providing a more intensive working of the containers than two single beam cranes side-by-side.
[0023] In a particularly preferred embodiment of the invention, a third mobile trolley and associated spreader is supported between the two beams on further rails fixed to the two beams, whereby the third trolley may move to and fro along the space between the beams on the said further rails.
[0024] Clearly with suitable beam spacing this arrangement will permit three adjacent rows of 20 foot containers to be worked simultaneously by the single crane or, as before, two adjacent rows of 40 foot containers.
[0025] A further advantage is that if one trolley is subject to mechanical or other breakdown, there will still be at least one operative trolley.
[0026] In the preferred embodiment referred to above, it is advantageous that rather than having one operator per trolley as in single beam cranes, there may be one mobile operator cabin supported between the two beams in the same manner as the third trolley and which during operation of the crane is located towards the front end of the beams for controlling all three trolleys during loading and unloading of containers from, for example, a vessel, and a second operator cabin (which may likewise be mobile and supported between the beams) towards the rear of the beams for controlling loading and unloading on the land side of the beams, control of each trolley being passed from one operator to the other at an intermediate point along the beam. The second operator cabin may alternatively be fixed to the gantry structure.
[0027] Thus not only does the multiple beam structure of the preferred embodiment permit more intensive working, this can be achieved with one less operator than using separate single beam cranes.
[0028] Naturally, since there will be little clearance between adjacent containers being simultaneously worked, they will need to be lifted to different heights for transport along the beams to avoid collision by sideways swaying. This can be controlled either automatically or by the operators, and an automatic safety system can readily be devised which would monitor and correlate the heights of the containers and their positions along the beams to provide an automatic cut-out or alarm if sufficient separation of the containers or of the trolley structures was not maintained at all times.
[0029] Clearly the principle described above can be extended to cranes having more than two parallel beams supported by the gantry, with a respective mobile trolley supported under each beam and a respective trolley supported in the space between each adjacent pairs of beams.
[0030] As mentioned previously, the invention is particularly applicable to quayside cranes, and therefore it is additionally preferred that the gantry is of generally arched configuration having two front and two rear legs respectively which travel on the fixed ground rails, wherein the beams extend at least under the front of the arch and preferably also project beyond the rear of the arch, and wherein the portion of each beam forwardly of the arch is a derrick boom which can be raised from its horizontal position to provide clearance to allow the docking of ships to be unloaded and vice versa.
[0031] An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings wherein:
Figure 1 is a perspective view of a quayside travelling container crane having two parallel beams,
Figure 2 is a side view of the crane of Figure 1,
Figure 3 is a plan view of the front part of the crane of Figure 1,
Figure 4 is a partial front view illustrating the crane of Figure 1 in operation loading and/or unloading 20 foot containers,
Figure 5 is a partial front view illustrating the crane of Figure 1 in operation loading and/or unloading 40 foot containers, and
Figure 6 is a schematic front view of a modification of the crane of Figure 1.
[0032] In the Figures it will be appreciated that the crane drive and control mechanisms are not shown, but they may be of conventional design and their adaptation to the embodiment shown would not present any great difficulty for the person skilled in the art. Thus they are usually electro-mechanical with either solid state or Ward Leonard speed regulation. Power supply to the crane may be by diesel generator or conductor rails or may be taken from the port's mains supply and fed to the crane by a flexible cable which is reeled/unreeled on a cable reeling drum on the crane. Power is distributed to the individual trolleys by further flexible cables which "concertina" along the length of the beams.
[0033] Referring first to Figures 1 to 3, the crane comprises a mobile gantry 10 of generally arched configuration, having two front legs 11 and two rear legs 12, and various bracing and cross members 13. The gantry 10 is adapted for sideways movement on a pair of rails fixed in or to the ground parallel to the quayside 15 (Figure 2), only the rail 14 most remote from the quayside 15 being shown. In particular, the front legs 11 travel on the rail (not shown) nearest the quayside 15, while the rear legs 12 travel on the rail 14 furthest from the quayside.
[0034] As mentioned above, the gantry legs 11 and 12 run on the ground rails by means of a system of rocker beams, wheel bogies and wheels. However, these are not shown in the Figures for simplicity and because they may be of generally conventional construction, except that there would typically need to be ten to sixteen wheels per leg rather than the conventional eight in order to carry the extra weight.
[0035] Two parallel beams 16 and 17 are supported by and extend side-by-side horizontally from the gantry 10 in a direction perpendicular to the direction of sideways motion of the gantry. In particular, the beams 16 and 17 extend under the cross member 13′ joining the tops of the front legs 11, fully through the arched gantry 10, and finally to emerge from under the cross member 13˝ joining the tops of the rear legs 12 to project beyond the rear of the arch.
[0036] The portion of each beam forwardly of the arched gantry 10 is a derrick boom which can be raised from the horizontal position shown to a nearly vertical position to provide clearance for masts, etc. to allow the docking of ships to be unloaded and vice versa.
[0037] The derrick booms, i.e. the forward portions of the beams 16 and 17, rotate upwardly about the hinge points 18 and 19 respectively during "derricking". However, during normal operation they are maintained horizontal by holding arms 20 attached to A-frames 21. The beams are approximately 20 feet in width in this embodiment, and are spaced apart by the same distance. However, in order to accomodate the side-shift to be described with reference to Figure 6, the width of the beams would need to be increased by an amount which depends on the length of side-shift required. Each beam 16 and 17 forms a runway for a respective mobile trolley 22 and 23 supported under the beam on two rails fixed longitudinally on the beam, whereby each trolley may travel along its rails to and fro along substantially the full length of the beam.
[0038] In particular, a respective inverted T-beam 24 is fixed to and depends from each outer edge of each beam 16 and 17, and wheels 25 on each side of each trolley 22 and 23 run on rails 26 supported by the two inward facing limbs 27 of the two T-beams 24 supported by the outer edges of the associated beam 16 and 17. A detailed view of this arrangement is shown at the top of figure 4, but generally this detail is omitted for simplicity.
[0039] Further rails 28 are fixed along the two outward facing limbs 29 of the T-beams 24 at the opposing edges of the two beams 16 and 17, and these form a runway for a third mobile trolley 30 having wheels 31 on opposite sides thereof which engage these rails 28. Thus this third trolley 30 is supported between the two beams 16 and 17 in a similar manner as each of the trolleys 22 and 23 is supported below its respective beam 16 and 17, and may thus travel along its rails 28 to and fro along substantially the full length of the space between the beams 16 and 17, i.e. between and parallel to the paths of travel of the two trolleys 22 and 23.
[0040] A similar supporting effect to that given by the T-beams as above described can be obtained in alternative ways, for example by having each of the two trolley support beams consist of two outer I-beams located vertically, with their upper portions braced together with a lattice construction, allowing the bottom of each I-beam to support two trolley rails.
[0041] Each of the three trolleys 22, 23 and 30 has a respective container hoist allocated thereto. These hoists may be entirely conventional, and comprise a winch/rope system 32 by which a so-called pulley frame and spreader 33 may be raised and lowered. Spreaders are known in the art, and are lifting frames which can be attached to the four corners at the top of a container by twistlocks. Spreaders either have fixed dimensions, so that they have to be changed for different container dimensions, or they can be telescopic to handle a range of container sizes.
[0042] For controlling the crane, there is a first mobile operator cabin 39 (shown only in figure 3) supported for travel along and between the two beams 16 and 17 in the same manner as the third trolley 30 and which during operation of the crane is located towards the front end of the beams for controlling all three trolleys during loading and unloading of containers from a vessel shown. If required for operational reasons, this cabin may be equipped with a side-shift facility to give the operator a clearer vertical view into the particular hold being served. Since the first operator cannot accurately control from his position the motion of the trolleys as they approach the gantry 10, a second operator cabin (which is not shown but may either be fixed to the gantry structure or mobile and supported between the beams like the trolley 30) is located towards the rear of the beams for controlling loading and unloading on the land side of the beams, control of each trolley being passed from one operator to the other at an intermediate point along the respective beam.
[0043] Figure 4 illustrates how the two beam/three trolley arrangement described can handle three 20 foot cargo containers in a continuous cycle of loading and/or unloading. In figure 4 it is assumed that the gap between the two beams 16 and 17 is located centrally over one row A of 20 foot containers, and the two beams 16 and 17 on either side are located centrally over two rows C and B of 20 foot containers immediately on either side of the first row (see also figure 3).
[0044] It is clear that provided that the containers 35 from the row A are lifted to a different height to the containers 34 and 36 from the rows C and B, they may travel freely back and forth along the beams in the same direction or in different directions, and loading may be combined with unloading (i.e. containers carried in both directions). However, since there is not enough clearance to permit all three containers to be lowered or raised at the same time, it is safer if the centre trolley 30 moves seawards as the outer trolleys 22 and 23 move landwards, and vice versa. This also tends to reduce the maximum load on the ends of the beams.
[0045] Figure 5 illustrates how 40 foot containers are handled. In this case the centre trolley 30 is not used and is parked on the land side of the beams 16 and 17. The beams 16 and 17 are positioned centrally over adjacent rows D and E of 40 foot containers, and containers 37 from row D may be carried inwardly to the land side simultaneously or alternately with containers 38 from row E. Again, the containers are kept at different heights, and loading may be combined with unloading.
[0046] In the case of the less common 35, 45 and 48 foot containers, trolleys 22 and 23 are parked, and only the centre trolley 30 is used. However, by incorporating a side-shift facility as described below, it is also possible to design the crane so that it can handle two 35 or 45 or 48 foot containers with the outer trolleys 22 and 23 in a manner similar to that described above for handling two 40 foot containers.
[0047] One possible problem arising out of the aforesaid crane with mulitple beams and trolley supports is that of "side-shift". Containers are not normally stacked on board ship with their ends touching, although this is theoretically possible and thus must be designed for. The spacing between the ends of adjacent containers is, therefore, a variable with a minimum value of 0 ft. and a maximum of about 6 ft., where container bays are separated from each other by ship's bulkheads or hatch cover mechanisms.
[0048] It is therefore, advantageous to provide a "side-shift" facility on the spreader 33 carried by the two outer trolleys 22 and 23 to allow them to operate on containers spaced by up to 6 ft., or more on either side of a centre container. One possible type of side-shift mechanism would be one where each of the two outer trolleys 22 and 23 are equipped with a separate machinery house 40 (figure 6) containing the hoist drums 41 and associated gear for that trolley (such machinery house trolleys are relatively common on conventional container cranes). The machinery house can be made to travel left-to-right and vice versa (i.e. sideways) on the trolley by fitting it with wheels 42 travelling on rails (not shown) mounted on the trolley proper. The overall width of the beams 16 and 17 is increased, in the direction away from the centre gap which remains at 20 foot, to permit the centre-line 43 of each hoist to be displaced outwardly by up to a distance L, e.g. at least 6 and preferably up to 11 feet. By this means it is possible to greatly increase the flexibility of the crane for container handling purposes. If side-shift is required for the centre trolley 30, the mechanism for achieving this side-shift may be incorporated either on the trolley itself or between the pulley frame (headblock) and the spreader. It will be understood that in figures 1 to 5 the machinery house 40 and drums 41 are not explicitly described but may be either located in a fixed position on or between the beams 16 and 17 or fixed to each trolley 22, 23 and 30, rather than being a separately movable part as shown in figure 6.
1. A travelling container crane of the kind comprising a mobile gantry (10) mounted
for sideways movement on fixed ground rails (14), a beam (16) supported by and extending
horizontally from the gantry (10) in a direction perpendicular to the direction of
motion of the gantry, a mobile trolley (22) supported under the beam (16) on rails
(26) fixed to the beam for to-and-fro movement of the trolley along the beam on the
beam rails, and a hoistable container-lifting device (33) suspended from the trolley,
characterised by at least two parallel beams (16, 17) supported in spaced apart side-by-side relationship
by the gantry (10), each beam having a respective mobile trolley (22, 23) and associated
hoistable container-lifting device (33).
2. A travelling crane according to Claim 1, further including a third mobile trolley
(30) and associated container-lifting device (33) supported between the two beams
(16, 17) on further rails (28) fixed to the two beams, whereby the third trolley may
move to and fro along the space between the beams on the said further rails.
3. A travelling container crane according to Claim 1 or 2, further including a first
mobile operator cabin (39) supported between the two beams (16, 17) for movement to
and fro along the space between the beams and locatable towards the front of the beams,
and a second operator cabin located towards the rear of the beams.
4. A travelling container crane according to Claim 1, 2 or 3, wherein the gantry is
of generally arched configuration having two front and two rear legs (11, 12) respectively
which travel on the fixed ground rails, (14) wherein the beams (16, 17) extend at
least under the front of the arch, and wherein the portion of each beam forwardly
of the arch is a derrick boom which can be raised from its horizontal position to
provide clearance to allow the docking of ships to be unloaded and vice versa.
5. A travelling container crane according to any preceding Claim, wherein at least
one of the mobile trollies has an associated hoistable container-lifting device (33)
which is shiftable sideways.
6. A travelling container crane according to Claim 5, wherein the mobile trolley comprises
a sideways shiftable housing (40) containing hoisting means (41) for the container-lifting
device (33).