EP2445823B1

EP2445823B1 - A method for fastening the claw of a lifting device to a lifting arm, and lifting device

Info

Publication number: EP2445823B1
Application number: EP10791673.6A
Authority: EP
Inventors: Kalle Pohjola
Original assignee: Rannikon Konetekniikka Oy
Current assignee: Rannikon Konetekniikka Oy
Priority date: 2009-06-25
Filing date: 2010-06-16
Publication date: 2014-08-13
Anticipated expiration: 2030-06-16
Also published as: FI20095726A0; IN2012DN00585A; WO2010149847A1; EP2445823A1; FI20095726A; RU2012101810A; FI124105B; EP2445823A4

Description

The invention relates to a lifting device comprising at least one lifting arm with a turnable lifting claw for supporting a piece to be lifted, such as a coil or a reel, the lifting claw being connected to the lifting arm by means of a first rotation axis. The invention also relates to a method for fastening a lifting claw to a lifting arm in a lifting device, to be turnable around a first rotation axis.
Coil lifters are used for manipulating coils and reels of a strip-like material, such as steel sheets. A conventional coil lifter fastened to a lifting device and having stationary claws comprises an upper frame equipped with two lifting arms movable in the lateral direction and pointing downwards. Lifting claws are provided at the ends of the lifting arms, to be fitted into the central opening of a coil to be manipulated. When gripping the coil, the lifting arms are first spaced so that the coil in the horizontal position is accommodated between the lifting arms. After this, the claws at the ends of the lifting arms are moved to face the central opening of the coil on opposite sides of the coil, and the lifting arms are moved against the end surfaces of the coil so that the lifting claws penetrate into the central opening of the coil. When the coil lifter is lifted, the lifting claws are supported to the wall of the inner opening of the coil, moving the coil with them.
There is often a need to store coils in rows very close to each other. This kind of a situation occurs, for example, when coils are loaded in means of transport, such as ships. When coil lifters with stationary claws are used, a relatively large gap is unavoidably left between the coils to be placed in a row, because of the space required for movement of the arms. To reduce the space, coil lifters with turnable claws have been developed, in which the lifting claw is fastened at its one end to the lifting arm in an articulated manner. The lifting claw is turned to a position projecting from the lifting arm when the coil lifter is used to grab a coil. When the coil is released from the lifter, the lifting claws are withdrawn into the lifting arm, wherein the lifting arms can be lifted from around the coil without being hindered by the lifting claws. The position of the lifting claws is changed by means of an actuator, such as a hydraulic cylinder, and a lever mechanism coupled to it. By using a coil lifter with turnable claws, the minimum distance between the coil rows can be reduced by about 20 cm. Documents EP 1033342 A2 and DE 4217333 A1 disclose coil lifters with turnable claws.
In coil lifters with turnable claws of prior art, the lifting claw is attached at its one end to the lifting arm in a journalled manner. The lifting claw must have sufficient space to turn from the horizontal position to the vertical position and back inside the central opening of the coil, wherein the free diameter of the central opening sets an upper limit for the length of the lifting claw. For this reason, the reach of the lifting claw into the coil may, in some cases, be insufficient. An insufficient reach of the lifting claw is pronounced in cases in which poorly reeled coils with uneven end surfaces must be manipulated. In many cases, such coils cannot be lifted safely by coil lifters with turnable claws of prior art, for which reason other methods of hoisting must be used.
The document JP S58 119 584 discloses a lifting device according to the preamble of claim 1 and a method according to the preamble of claim 8.
It is an objective of the invention to introduce a method for fastening a lifting claw to the lifting arm of a lifting device in a turnable manner, and a lifting device, by means of which it is possible to significantly reduce the drawbacks and disadvantages related to the prior art.
The objectives of the invention are achieved by a method and a lifting device which are characterized in what will be set forth in the independent claims. Some preferred embodiments of the invention will be presented in the dependent claims.
The lifting device according to the invention comprises at least one lifting arm with a turnable lifting claw for supporting a piece to be lifted, such as a coil or a reel. The lifting claw is connected to the lifting arm by a first rotation axis in such a way that the lifting claw can be turned around the rotation axis to either a projecting position or a withdrawn position. In the invention, the first rotation axis is supported to the lifting arm to be movable in the longitudinal direction of the lifting arm. Furthermore, the lifting claw comprises a second rotation axis at a distance from the first rotation axis. The second rotation axis is supported to the lifting arm to be movable in the direction transverse to the lifting arm. When the lifting claw is withdrawn or exposed, it is turned around the first and second rotation axes. At the same time with the turning, the first rotation axis moves in the longitudinal direction of the lifting arm and the second rotation axis moves in a transverse direction of the lifting arm.
According to the invention, the lifting arm comprises a first elongated axis slot, in which the first end of the rotation axis is fitted, and a second elongated axis slot, in which the second end of the first rotation axis is fitted. The first and second axis slots are substantially parallel to the longitudinal axis of the lifting arm.
Advantageously, the lifting arm comprises a recess, in which the lifting claw is placed, and the recess comprises a first side wall, in which the first elongated axis slot is formed, and a second side wall, in which the second elongated axis slot is formed.
In a second advantageous embodiment of the lifting device according to the invention, at least one rocker lever is provided, having a first end and a second end. The first end of the rocker lever is connected to the lifting arm in a turnable manner, spaced from the axis slots, and the second end is connected to the second rotation axis in a turnable manner. Advantageously, the side wall of the recess is provided with a supporting pin whose end extends to the inside of the recess, and the first end of the rocker lever is attached to the supporting pin.
In a third advantageous embodiment of the lifting device according to the invention, two lifting arms are provided, having an inner surface. The inner surfaces of the lifting arms delimit between them a space in which the piece to be lifted is placed. The lifting claws of the lifting device can be turned to a first extreme position, in which they extend to the inside of the area delimited by the inner surfaces of the lifting arms, and to a second extreme position, in which they are substantially entirely outside the area delimited by the inner surfaces of the lifting arms. Advantageously, the lifting device is a coil lifter whose lifting claw can be fitted inside the central opening of a coil or a reel.
In the method according to the invention, the lifting claw is fastened to the lifting arm of the lifting device in such a way that the lifting claw can be turned around the first rotation axis to the projecting or withdrawn position. In the method, the first rotation axis is connected to the lifting arm to be movable in the longitudinal direction of the lifting arm. Furthermore, a second rotation axis, spaced from the first rotation axis, is formed to the lifting arm and connected to the lifting arm to be movable in a direction transverse to the lifting arm. According to the invention the movable connection of the first rotation axis is implemented in such a way that a first elongated axis slot substantially parallel to the longitudinal direction of the lifting arm is formed to the lifting arm, in which slot the first end of the first rotation axis is fitted, and a second elongated axis slot substantially parallel to the longitudinal direction is formed to the lifting arm, in which slot the second end of the first rotation axis is fitted.
The invention has the advantage that it increases substantially the reach of the lifting claw of the lifting device inside the coil. Thus, the invention makes it possible to lift even poorly reeled coils safely without special arrangements.
Furthermore, the invention has the advantage that the mechanism of fastening the lifting claw in the lifting arm is very firm, which improves the lifting capacity of the coil lifter.
Furthermore, the invention has the advantage of a simple and reliable construction as well as low manufacturing costs.
In the following, the invention will be described in detail. In the description, reference will be made to the accompanying drawings, in which:

Fig. 1 shows, as an example, a lifting device according to the invention diagonally from the front,
Fig. 2a shows the end of the first lifting arm of the lifting device of Fig. 1 in a partially enlarged view,
Fig. 2b shows the end of the second lifting arm of the lifting device of Fig. 2 in a partially enlarged view.

In Fig. 1, an example of a lifting device according to the invention is shown diagonally from the front. The lifting device shown in the figure is a coil lifter used for manipulating coils and reels. The figure shows the coil lifter in its normal use position, that is, in the position in which the coil lifter is used for gripping coils to be lifted. The coil lifter comprises an upper frame 10 made up of sheet-like parts welded together, having two parallel suspending lugs 12 at its first edge which is uppermost in the operating position. The suspending lugs comprise concentric through holes, in which a detachable securing bolt 14 is placed. The suspending lugs and the securing bolt constitute the suspending means of the coil lifter, by which the coil lifter is attached to a lifting device, such as a crane.
At the second edge of the upper frame, which is lowermost in the operating position, there are two supporting beams 16a, 16b extending horizontally. To the ends of the supporting beams, lifting arms 18a, 18b are connected in such a way that the beams form a substantially right angle with the lifting arms. The free ends of the lifting arms point from the upper frame in the direction opposite to the suspending lugs, that is, downwards in Fig. 1. The supporting beams are supported to the upper frame in such a way that they can be moved in the direction of their longitudinal axis, wherein the lifting arms at their ends are movable towards each other or away from each other. Lifting claws 20, which are turnable towards each other, are provided at the free ends of the lifting arms and placed in recesses 22 in the lifting arms. The structure of the upper frame, the supporting beams and the lifting arms of the coil lifter is prior art known as such, wherein it will not be described in more detail in this context.
Figures 2a and 2b show the free ends of the lifting arms 18a, 18b in a partially enlarged view. The ends of both lifting arms are identical in structure but mirror images of each other. A recess 22 having the shape of a rectangle with rounded corners is provided at the end of the lifting arm, the lifting claw 20 being placed in it. In Figs. 2a and 2b, the recess extends from the inner wall of the lifting arm to the outer wall of the lifting arm; that is, it forms a hole extending through the lifting arm. The recess comprises a first side wall 24 and a substantially parallel second side wall 25, a first end wall 26 and a substantially parallel second end wall 27. In this description, the first end wall refers to the end wall closest to the free end of the lifting arm.
The first end wall comprises an elongated first axis slot 28 extending through the wall, and the second side wall comprises a similar second axis slot 29 in a corresponding location. The first ends of the axis slots are close to the first end wall 26, and their second ends are spaced from the first end wall in the direction of the longitudinal axis of the lifting arm. In Figs. 2a and 2b, the length of the axis slot in the direction of the length of the lifting arm is about ¼ of the height of the recess 22, that is, of the distance between the first and second end walls. Furthermore, the first and second end walls are each also provided with a supporting pin 38. The supporting pins are placed in the hole extending through the side wall in such a way that their ends extend through the side wall to the inside of the recess 22. The supporting pins are placed concentrically at a distance from the second end wall 27. In Figs. 2a and 2b, the distance between the supporting pins and the second end wall is about 1/4 of the height of the recess 22.
The recess 22 comprises a beam-like lifting claw 20. At the first end of the lifting claw, there is a first rotation axis 30 extending transversely to the longitudinal direction of the lifting claw, the first end of the rotation axis extending into the axis slot in the first side wall 24 and the second end extending into the axis slot in the second side wall 25. At the second end of the lifting claw, there is a lifting surface 32 that is supported, in a lifting situation, to the wall surface of the inner hole extending through the reel to be lifted. The lifting surface is shaped as an upwards curved surface. In the area between the first and second ends of the lifting claw, there is a second rotation axis 34, whose first end extends to the first side of the lifting claw and second end to the second side of the lifting claw. The ends of the second rotation axis are connected to the lifting arm by means of two rocker levers 36 in such a way that the first end of the rocker lever is connected to the supporting pin 38 on the side wall of the recess 22 in a turnable manner, and the second end of the rocker lever is connected to the end of the second rotation axis in a turnable manner.
The lifting claw is further provided with two bar-like lifting rods 40 parallel to the lifting arm, for adjusting the position of the lifting claw. The lifting rods are connected at their first end to the first end of the lifting claw in an articulated manner. The second ends of the lifting rods are connected to an actuator 42 inside the lifting arm, for moving the lifting rods in the direction of their longitudinal axis. The actuator shown as an example in Figs. 2a and 2b is a hydraulic cylinder, but it may also be another actuator, such as a pneumatic cylinder or a motorized drive screw mechanism.
Figures 2a and 2b show the lifting claws of a coil lifter according to the invention in their projecting position. The lifting claws are in this first extreme position when they are used for grabbing a coil or reel to be lifted. The ends of the first rotation axis 30 are at the second end of the axis slot 28, 29 in such a way that the surface of the first rotation axis is supported to the wall of the second end of the axis slot. The second rotation axis 34 is outside the recess 22, at a distance from the imaginary line passing through the ends of the first rotation axis and the supporting pin 38. The lifting surface 32 at the second end of the lifting claw is thus in a substantially horizontal position and extends clearly to the inside of the area delimited by the inner walls 19a of the lifting arms 18a, 18b.
After the coil or reel has been transferred to a desired location, the coil lifter can be released. At the releasing stage, the coil is lowered onto a support so that the lifting surface loses contact with the coil. The first ends of the lifting claws are then moved towards the first end wall 26 by moving the lifting arms 40 with the actuator 42. The elongated shape of the axis slot 28, 29 enables the movement of the first end of the lifting claw and the first rotation axis. During the simultaneous movement of the first rotation axis in the direction of the lifting arm, the lifting claw turns around the second rotation axis 34 and moves towards the second extreme position parallel to the lifting arm, in which the lifting claw and the rocker levers 36 are substantially parallel to the lifting arm inside the recess 22. The first rotation axis is thus located at the first end of the axis slot, and the second rotation axis is on the imaginary line that passes through the ends of the first rotation axis and the supporting pin 38. In the second extreme position, the lifting claws and the rocker levers supporting them are thus totally outside the area delimited by the inner surfaces 19a of the lifting arms 18a, 18b. In this position, the lifting arms can be lifted away from around the coil or reel without moving the lifting arms in the lateral direction.
The lifting claws are brought back to the projecting first position by moving the lifting arms 40 by the actuator towards the upper frame, wherein the first rotation axis 30 moves from the first end of the axis slot towards the second end of the axis slot. Simultaneously, the lifting claw 20 turns around the first and second rotation axes and projects from the recess 22. During the projection, the second rotation axis, supported by the rocker levers 36, moves along a path with the shape of a circular arch in a direction transverse to the lifting arm.
The method according to the invention for fastening the lifting claw is particularly suitable for use in coil lifters with two lifting arms equipped with a turnable lifting claw according to the invention. It is also possible to manufacture coil lifters with only one lifting arm according to the invention, wherein the second lifting arm may have a stationary claw or be fastened to the lifting arm in a turnable manner according to prior art.
Some of the advantageous embodiments of the method and lifting device according the invention have been described above. The invention is not restricted to solutions described above, but the inventive idea can be applied in numerous ways within the scope defined by the claims.

Claims

A lifting device, comprising at least one lifting arm (18a, 18b) with a turnable lifting claw (20) for supporting a piece to be lifted, such as a coil or a reel, the lifting claw being connected to the lifting arm by means of a first rotation axis (30), whereby the first rotation axis is supported to the lifting arm to be movable in the longitudinal direction of the lifting arm, and the lifting claw further comprises a second rotation axis (34), the second rotation axis being spaced from the first rotation axis and being supported to the lifting arm to be movable in a direction transverse to the lifting arm characterized in that the lifting arm (18a, 18b) comprises a first elongated axis slot (28), in which the first end of the first rotation axis (30) is fitted; and a second elongated axis slot (29), in which the second end of the first rotation axis is fitted; the first and second axis slots being substantially parallel to the longitudinal axis of the lifting arm.
The lifting device according to claim 1 characterized in that it comprises at least one rocker lever (36) with a first end connected to the lifting arm (18a, 18b) in a turnable manner, at a distance from the axis slots (28, 29), and a second end connected to the second rotation axis (34) in a turnable manner.
The lifting device according to claim 1 or 2, characterized in that the lifting arm (18a, 18b) comprises a recess (22), in which the lifting claw (20) has been placed, the recess comprising a first side wall (24) and a second side wall (25), wherein the first elongated axis slot (28) is formed to the first side wall (24) and the second elongated axis slot (29) is formed to the second side wall (25).
The lifting device according to claim 3, characterized in that the side wall (24, 25) of the recess (22) comprises a supporting pin (38), the end of the supporting pin extending to the inside of the recess, and the first end of the rocker arm (36) being connected to the supporting pin.
The lifting device according to any of the claims 1 to 4, characterized in that it comprises two lifting arms (18a, 18b) having an inner surface (19a); and the lifting claws (20) are turnable to a first extreme position, in which they extend to the inside of the area delimited by the inner surfaces of the lifting arms, and to a second extreme position, in which they are substantially entirely outside the area delimited by the inner walls of the lifting arms.
The lifting device according to any of the claims 1 to 5, characterized in that it comprises at least one lifting arm (40) connected to the lifting claw (20), and an actuator (42) for moving the lifting arm (40).
The lifting device according to any of the claims 1 to 6, characterized in that it is a coil lifter whose lifting claw (20) can be fitted into the central opening of a coil or a reel.
A method for fastening a lifting claw (20) to a lifting arm (18a, 18b) of a lifting device to be turnable around a first rotation axis (30), whereby the first rotation axis is connected to the lifting arm to be movable in the longitudinal direction of the lifting arm, and to the lifting arm a second rotation axis (34), spaced from the first rotation axis, is formed and connected to the lifting arm to be movable in a direction transverse to the lifting arm, characterized in that to the lifting arm (18a, 18b) a first elongated axis slot (28) is formed substantially parallel to the longitudinal direction of the lifting arm, in which slot the first end of the first rotation axis (30) is fitted, and a second elongated axis slot (29) is formed substantially parallel to the longitudinal direction of the lifting arm, in which slot the second end of the first rotation axis is fitted.
The method according to claim 8, characterized in that the second rotation axis (34) is connected to the lifting arm (18a, 18b) by means of at least one rocker lever (36).