Low-construction trolley for wire rope hoist

A low-construction hoist for a wire rope hoist is arranged to move along a lower flange of a horizontal beam or rail. The trolley includes a trolley frame; bearing wheels, which are fixed to the trolley body and arranged to move on the upper surface of the lower flange of the rail, a hoisting mechanism including a rope drum for a hoisting rope, a hoisting member in cooperation with the hoisting rope for hoisting a load, and a hoisting motor for driving the rope drum; whereby the rope drum is supported to a first side of the trolley frame so that the axle of the rope drum is parallel to the rail, and the hoisting member is arranged to move under the rail; whereby the hoisting rope is led from the rope drum to a fixing point in the trolley frame through at least a rope pulley arrangement of the hoisting member, whereby the fixing point of the hoisting rope to the trolley frame is located in the longitudinal direction of the trolley outside the end of the rope drum, or outside the vertical plane which is transverse in relation to the rail or beam and passing through the end of the rope drum.

BACKGROUND OF THE INVENTION

A low-construction trolley for a wire rope hoist, arranged to travel along a lower flange of a horizontal beam or rail, whereby the trolley comprises a trolley frame; bearing wheels that are attached to the frame of the trolley and arranged to travel on the upper surface of the lower flange of the beam or rail, and at least some of which are driven wheels to move the trolley; a hoisting mechanism comprising a rope drum for a hoisting rope, a hoisting member in cooperation with the hoisting rope for hoisting a load, and a hoisting motor for driving the rope drum; whereby the rope drum is supported to a first side of the trolley frame so that the axle of the rope drum is parallel to the beam or rail, and the hoisting member is arranged to move under the beam or rail; whereby the hoisting rope is led from the rope drum to a fixing point in the trolley frame through at least a rope pulley arrangement of the hoisting member.

A low-construction trolley is a common, overhead trolley type for lightweight bridge cranes with one main support. The basic idea behind it is to save hall height by taking up as little space as possible in the vertical direction.

As a result of the external shape taking up little space, the heaviest parts of a trolley in prior art, that is, the hoisting mechanism and rope drum, are found on the same side of the main support (which is the same as the aforementioned beam of rail or comprises the aforementioned beam or rail). This causes imbalance on the opposite sides of the main support, which is typically compensated for by a counterweight on the opposite side of the main support and opposite to the hoisting mechanism. When examining the hoist in the vertical direction, the rope system and hoisting member of the hoisting rope are in such a case arranged in an area limited by the ends of the counterweight, hoisting mechanism, and rope drum, whereby the fastenings of the hoisting rope to the rope drum and the trolley frame are also located in this area. Due to this space problem, the fixing point of the hoisting rope to the trolley frame is found closer to the main support than the disengagement point of the hoisting rope from the drum. For example, in a 4-rope solution, the fixing point of a sheave, in such a case, is to be placed at the mean distance of the aforementioned fixing point and disengagement point from the main support on the opposite side of the main support for the hoisting member to move essentially in the vertical plane that runs through the main support and for the trolley to stay in balance. This asymmetry and long lever arms in relation to the main support cause, however, additional twisting of the rope system in relation to the vertical axis in a load hoisting and lowering situation, and consequently harmfully large bending moment and the resulting additional stress on the trolley, on the bearing wheels, for example, and thus additional stress also on the main support. Disproportional load may cause premature wear and tear on the bearing wheels and/or the guiding surfaces on the beam or rail that the main support potentially has, creating jerking movement for the trolley.

In addition, if the fixing of the hoisting rope to the rope drum is typically located on the side of the trolley where the fixing point of the hoisting rope to the trolley frame is also located, the portion of the rope system that leads to a fixed fixing point may hit the portion of the rope system coming from the rope drum when the hoisting member is being lowered, which may wear and damage the hoisting rope. In this solution, the rope base, that is, the projection of the rope system in the horizontal plane is reduced as the hoisting member is lowered, which at the same time decreases the geometric resistance of the hoisting member twisting.

The “asymmetric” rope system described above is also implemented in such trolleys where the counterweight is replaced with a suspended contact to the main support, that is, the lower surface of the lower flange of the horizontal beam or rail referred to in the above. The U.S. Pat. No. 7,234,400 B2 and EP 0 620 179 B1 serve as examples of this solution. In these, too, exactly the same problems are seen as in trolleys comprising a counterweight.

SUMMARY OF THE INVENTION

The object of the invention is to solve the problems described above. This object is achieved with a trolley according to the invention, which is mainly characterised by the fact that the fixing point of the hoisting rope to the trolley frame is located in the longitudinal direction of the trolley, respectively beam or rail, outside the end of the rope drum, or outside the vertical plane which is transverse in relation to the rail or beam and passing through the end of the rope drum.

Advantageously, the fixing point of the hoisting rope to the trolley frame is located in the longitudinal direction of the trolley, respectively beam or rail, at a distance from the end of the rope drum, or the vertical plane which is transverse in relation to the rail or beam and passing through the end of the rope drum. This distance may be 0-1.5 times the diameter of the rope drum, for example.

The aforementioned transferring of the fixing point of the hoisting rope to the outside of the vertical plane which is transverse in relation to the rope drum end or rail or beam and passing through the end easily enables the most advantageous solution that the fixing point of the hoisting rope to the trolley frame is at essentially the same vertical plane as the disengagement point of the hoisting rope from the rope drum, as seen in the line parallel to the axle of the rope drum and parallel to the rail, in particular when the hoisting rope is guided from the rope drum through a rope pulley arrangement of the hoisting member and through at least one sheave on at least one side of the trolley frame to a fixing point on the same side of the trolley as the rope drum. In other words, when seen from the above, the fixing point of the hoisting rope to the trolley frame is essentially in the same line as the inner side line of the rope drum or the disengagement point of the hoisting rope from the rope drum as examined in the aforementioned direction. At the same time, this also means that the fixing point of the hoisting rope to the trolley frame is at essentially the same distance from the rail as the disengagement point of the hoisting rope or the inner side line of the rope drum.

The solution according to the invention makes it possible to establish symmetrical positioning of the support points of the hoisting rope in relation to the main support whereby the twisting of the hoisting member and the load attached to it, described in the above, may be substantially reduced during a hoisting event. In addition, no danger exists at any stage of the hoist of the hoisting rope crossing, even if the fixing point of the hoisting rope to the rope drum were on the side of the rope drum end where the fixing point of the hoisting rope to the trolley frame is located at a chosen distance outside the end in question.

In the most advantageous case, however, the fixing point of the hoisting rope to the rope drum is located on the side of the rope drum end that is on the opposite side than the rope drum end or the vertical plane which is transverse in relation to the beam or rail and passing through it, and outside of which rope drum end or vertical plane and closer to which the fixing point of the hoisting rope to the trolley frame is located. In such a case, the hoisting rope unreeling out and downward of the rope drum travels, in the direction of the main support, further away from the fixing point of the rope to the frame, whereby at the same time the rope base of the rope system increases, which reduces the twisting risk of the hoisting member and the load secured to it. Similarly, as the hoisting member and load are being hoisted up, at their highest position the projections of the various parts of the rope system are essentially perpendicular to the main support and the rope drum, whereby the twisting of the lifting hook and the load secured to it is substantially reduced, and the twisting stress directed at the trolley and the beam or rail is decreased.

The solution according to the invention additionally allows the diameter of the rope drum to be increased and the rope drum shortened, which reduces the drifting of the hoisting rope in the direction of the main support, and consequently the twisting risk of the hoisting member and the load secured to it.

In addition, the rope drum may now be brought closer to the main support, because the need no longer exists to reserve space for the fixing of the hoisting rope between the main support and rope drum. Correspondingly, the sheave or sheaves may be brought closer to the main support. The trolley-internal bending moment is thus further reduced. The new fixing point of the hoisting rope to the trolley frame also leaves more space around this fixing point, which may be utilized for safety equipment such as overload protection, for example. From the viewpoint of space becoming free, it is also possible to build a hoist with more than four ropes, for example, a 6-rope or 8-rope hoist. This means that the same hoisting mechanism may be used to hoist larger loads by changing the rope system, only.

From the point of view of balancing and stressing the trolley, it is further advantageous that the hoisting motor is placed under the beam or rail and at least partly on a different side than the rope drum, in relation to the vertical plane passing through the contact lines of the bearing wheels on the rope drum side, touching the lower flange of the beam or rail, most advantageously at least partly on a different side in relation to the vertical plane passing through the centre of the beam or rail than the rope drum. A relatively heavy hoisting motor entirely replaces the counterweights and spring supports used earlier. This solution additionally enables the rope drum to be more freely placed in the longitudinal direction of the beam or rail of the main support and the trolley, whereby there are more options to secure the fixing point of the hoisting rope to the trolley frame, outside the rope drum end.

The hoisting motor may be placed so that its longitudinal centre line is parallel to the longitudinal direction of the beam or rail, in such a manner, for example, that the hoisting motor is essentially in the same vertical plane as the beam or rail, whereby the vertical plane passing through the middle of the beam or rail is passing essentially through the longitudinal centre line of the hoisting motor. It is additionally feasible to move the hoisting motor away or closer to the rope drum, in relation to the vertical plane referred to in the above, as far away as needed until the desired balance is reached, if this is possible taking into account the power transmission and the structure of the trolley otherwise. The hoisting motor may additionally be positioned sideways in relation to the beam or rail.

By such positioning of the hoisting motor, uniform enough a bearing contact of the bearing wheels is achieved at the flange of the supporting beam or rail, whereby the wear on the bearing wheels is even, and the trolley, and thus the hoist, travel without jerking both when unladen and when carrying a load. So, there will be no additional stress on the trolley frame, caused by imbalance, when a load is being lifted or lowered. Installing a hoist is easier than before and lifting it up during the installation process, for example, is safer as the additional mass caused by a counterweight is missing.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, at first toFIGS. 1-3, in particular, a low-construction trolley1for a wire rope hoist is seen, arranged to travel along the lower flange3of a horizontal beam or of a rail2, like here. The rail2typically establishes the main support of a bridge crane, or is included in it as its lowest part.

The trolley1is shown as a simplified functional diagram, showing only what is needed to understand the invention.

The trolley1comprises a frame4of the trolley, bearing wheels5, and a hoisting mechanism6.

The bearing wheels5are attached to the frame4of the trolley, and arranged to travel on the upper surface of the lower flange3of the rail2, on both of its longitudinal edges, and at least some of are driven wheels to move the trolley1. The actuator (moving mechanism of the trolley) for driving the bearing wheels5is not shown.

The hoisting mechanism6comprises a rope drum7for a hoisting rope8, a hoisting member in cooperation with the hoisting rope8, i.e. a lifting hook9in this case, to hoist a load, a hoisting motor10to drive the rope drum7, and a gear11to connect the hoisting motor10to the rope drum7.

The rope drum7is fixed as supported by both of its ends to one side of the trolley frame4, whereby the centre axis of the rope drum7is parallel to the rail2, and the lifting hook9is arranged to travel under the rail2, in the vertical plane A passing through the middle thereof.

In the conventional and common 4-rope driving of the hoisting rope8(seeFIGS. 3-6, in particular), in which the hoisting rope is continuously subject to seven turns, the hoisting rope8is led from the rope drum7down to a first rope pulley12of the lifting hook9, from there up to a sheave13on the other side of the trolley1, further down from the sheave13to a second rope pulley14of the lifting hook9, and finally up to the fixing point X on the frame4of the trolley1on the same side of the trolley1as the rope drum7. The lifting hook9moves up or down depending on whether the hoisting rope8is reeled onto the rope drum7or out of it. The weight that the load creates is here distributed on four ropes.

In the 6-rope driving of the hoisting rope8according toFIGS. 8 and 9, the hoisting rope8is led from the rope drum7down to a first rope pulley120of the lifting hook9, from there up to a first sheave130on the other side of the trolley1, further down from the sheave130to a second rope pulley140of the lifting hook9, from there to a second sheave150on the first side of the trolley1, from the sheave150back down to a third rope pulley160of the lifting hook9, the rope pulley160being located closer to the vertical axis of the lifting hook9than the first rope pulley120, and from there finally up to the fixing point Z on the frame4of the trolley1on the other side of the trolley1in relation to the rope drum7.

In the 8-rope driving of the hoisting rope8according toFIGS. 10 and 11, the hoisting rope8is led from the rope drum7down to a first rope pulley220of the lifting hook9, from there up to a first sheave230on the other side of the trolley1, further down from the sheave230to a second rope pulley240of the lifting hook9, from there to a second sheave250on the first side of the trolley1, from the sheave250back down to a third rope pulley260of the lifting hook9, the rope pulley260being located closer to the vertical axis of the lifting hook9than the first rope pulley220, from there to a third sheave270on the other side of the trolley1, the sheave270being closer to the vertical plane A passing through the rail2than the first sheave230, from the sheave270down to a fourth rope pulley280of the lifting hook9, the rope pulley280being closer to the vertical axis of the lifting hook9than the second rope pulley240, and from here finally to the fixing point X on first side of the trolley1on the same side of the trolley as the rope drum7.

It is essential for the trolley according to the present invention that the fixing point X; Z of the hoisting rope8to the frame4of the trolley is located in the longitudinal direction of the trolley1and rail2outside the end of the rope drum7(4-rope and 8-rope one of the presented examples), or outside the vertical plane which is transverse in relation to the rail2and passing through it (6-rope one of the presented examples), at a chosen distance from the end or the rope drum7or said plane. This distance is advantageously approximately 0-1.5 times the diameter of the rope drum7.

In the most advantageous case, the fixing point X of the hoisting rope8to the trolley frame4is at essentially the same vertical plane as the disengagement point of the hoisting rope8from the rope drum7, as seen in the line parallel to the axle of the rope drum7and rail2.

As shown inFIGS. 5 and 6as well as9and11, the fixing point Y of also the hoisting rope8to the rope drum7is located on that side of the rope drum7end which is on the opposite side than the rope drum7end outside of which, or outside the vertical plane which is transverse in relation to the rail2and passing through it, and closer to which the fixing point X; Z of the hoisting rope8to the trolley frame4is located.

As shown inFIGS. 4, 8, and 10, the fixing point X; Z of the hoisting rope8to the frame4of the trolley is located at the chosen distance above the horizontal plane passing through the axle of the rope drum7, advantageously at the same height as the disengagement point of the hoisting rope8from the rope drum7at the highest position of the lifting hook9.

With the fixing of the hoisting rope8described in the above, in particular with its new fixing point X; Z to the frame4of the trolley, the twisting of the lifting hook9and the load secured to it and the resulting twisting stress on the trolley1is substantially reduced during the entire lifting event. Also, there is no danger of the hoisting rope8crossing at any phase of the hoist. This and advantages achieved by this were already described in closer detail in the above.

To achieve balance for the trolley1, it is further advantageous for the invention that the hoisting motor10is placed under the beam or rail2and at least partly on a different side than the rope drum7, in relation to the vertical plane passing through the contact lines of the bearing wheels5on the rope drum7side, touching the lower flange3of the beam or rail2, most advantageously at least partly on a different side in relation to the vertical plane A passing through the middle of the rail2than the rope drum7.

In the present example, the hoisting motor10is placed so that its longitudinal centre line is parallel to the longitudinal direction of the rail2, and to be more precise, so that the hoisting motor10is placed at essentially the same vertical plane as the rail2, whereby the vertical plane A passing in the middle of the rail2runs essentially through the longitudinal centre line of the hoisting motor10. The sideward location of the hoisting motor10may, however, be changed as needed to achieve the desired balance.

In this example solution, the gear11that interconnects the hoisting motor10and the rope drum7is arranged so that the hoisting motor10and the rope drum7are on the same side in relation to the gear11, whereby the hoisting motor10, gear11, and rope drum7are in a C form, as seen from the above. The hoisting motor10could also be located on the other side of the gear11, in which case the hoisting motor10, gear11, and rope drum7would be in a Z form as seen from the above. The hoisting motor10could also be located transverse in the same line with the gear11, in which case the hoisting motor10, gear11, and rope drum7would be in an L form as seen from the above.

In the implementation example ofFIG. 7, to further reduce stress, the rope drum7with its frame parts4aand the hoisting motor (not shown) linked to the rope drum7and located at the desired place, are advantageously fixed to one corner of the trolley frame4by a separate joint15, which is located closer to that end of the rope drum7from the side of which the hoisting rope8comes out when the lifting hook9is at its highest position. The location of the joint15is optimized so that the total torsional moment on the frame of the trolley1will be as small as possible. The total torsional moment consists of the combined effect by the bending moment and the torsional moment of the hoisting motor10. The bending moment depends on the load and the disengagement point of the hoisting rope8as expressed in the longitudinal direction of the rope drum7. The torsional moment depends on the moment of the hoisting motor10used for lifting. The purpose of optimizing the location of the joint is to avoid the situation where both the bending moment and the torsional moment are large at the same time, in which case the structure is under a particularly heavy load. Optimization seeks to achieve such a loading situation where, if one loading moment is big, the other moment would, on its part, be small. Such a comparison of the moments from the viewpoint of the structure optimum may be done, no matter which moment is big as long as the other one is similarly small.

The joint structure may be implemented, for example, so that the joint15is on both sides in contact with longitudinal stiffening members, which for their part connect to the rope drum7and trolley1at another location. In other words, the rope drum7has its own stiffening longitudinal stiffening member, such as a beam. This deviates from the prior art structure. This deviates from the prior art structure in that the rope drum7is conventionally fixed and braced to the side of a trolley. The hoisting rope8unreeling from the rope drum7and, consequently, rope force has affected the trolley at different moment arms and different directions, causing the trolley to twist. The twist has typically been evident in the trolley changing its shape, so that one of or some of the bearing wheels5rise out of the lower flange3of the rail2. According to the invention, this rope force conveyed from the rope drum7through the hoisting rope8is first transferred to the structure surrounding the rope drum7, which then connects to the trolley1by means of the joint15.

The above description of the invention is only intended to illustrate the basic idea of the invention. A person skilled in the art may thus vary its details within the scope of the attached claims. So, there is no need for the hoisting motor, for example, to be located as presented in the above due to the rope system according to the invention, although that is advantageous. Therefore, in this invention, the hoisting motor may also be considered to be conventionally placed.