WO1993016950A1

WO1993016950A1 - A crane, a lifting frame for a crane, and a method of lifting a component

Info

Publication number: WO1993016950A1
Application number: PCT/GB1993/000310
Authority: WO
Inventors: Robert Douglas Mckenzie
Original assignee: Rolls-Royce And Associates Limited
Priority date: 1992-02-20
Filing date: 1993-02-15
Publication date: 1993-09-02
Also published as: GB9203586D0

Abstract

A lifting frame (18) for a crane (10) comprises a wheeled gantry (20) which is arranged to move in a first direction on tracks (32) on the lifting frame (18) and a wheeled carriage (22) which is arranged to move in a direction perpendicular to the first direction on tracks (38) on the gantry (20). The lifting frame (18) is attached to a component (16) by attachment means (26) and a lifting point (23) on the carriage (22) is attached to a crane hook (14) by a shackle (24). A force transducer (52) measures the tension in the shackle (24), and accelerometers (58, 60) detect tilting of the lifting frame (18). A processor (56) calculates the position of the centre of gravity of the combined lifting frame (18) and component (16) from measured values of tension and automatically positions the lifting point (23) of the carriage (22) above the centre of gravity of the combined lifting frame (18) and component (16) to maintain the component (16) horizontal when it is lifted from the ground. The lifting frame (18) may be used with gantry cranes or goliath cranes.

Description

A CRANE, A LIFTING FRAME FOR A CRANE, AND A METHOD OF LIFTING A COMPONENT The present invention relates to cranes and in particular is concerned with lifting frames for cranes.

A lifting frame is an interface between a crane and a component to be lifted. In simplistic terms a lifting frame is a joist which is attached to the component to be lifted and is attached to a crane hook.

In the prior art it is known to have a lifting joist arranged so that the joist straddles the centre of gravity of the component and the crane hook is attached to a lifting point in the middle of the joist directly above the centre of gravity of the component. This prevents an imbalance of moments when the component is lifted from the ground and ensures that the component remains horizontal. It is also known in the prior art to have a lifting frame in which the lifting point of the lifting frame is moved in a straight line over a short distance. This arrangement uses a turnbuckle movement to move the lifting point in a straight line through ± 25 mm. This arrangement is suitable for a small range of components whose centre of gravity lie along the same axis and whose centre of gravity lie within the range of the turnbuckle movement.

It is also known from GB1550846 to provide a lifting frame which comprises a gantry mounted on, and movable in a first direction on, the lifting frame, a carriage mounted on, and movable in a second direction transverse to the first direction, on the lifting frame and a lifting point on the carriage. The present invention seeks to provide a novel lifting frame and novel crane.

Accordingly the present invention provides a lifting frame for use between a crane and a component to be lifted, the lifting frame comprising a lifting point, means to move the lifting point in a first direction on the lifting frame and means to move the lifting point in a second direction transverse to the first direction on the lifting frame, the lifting frame has means to removably attach the lifting point to a crane hoist, means to removably attach the lifting frame to a component to be lifted, the lifting frame has means to measure the tension in the means attaching the lifting point to the crane hoist, the means to measure the tension being arranged to produce an output signal which is supplied to processor means, the lifting frame has means to determine the position of the lifting point relative to the frame, the means to determine the position of the lifting being arranged to supply an output signal to the processor, the lifting frame has means to detect unequal lift applied by the lifting frame to the sides of the component- which unequal lift causes tilting of the component, the means to detect unequal lift being arranged to produce an output signal which is supplied to the processor means, the processor means being arranged to stop lifting of the component to minimise the angle of tilt to ensure the component remains in contact' with a surface, the processor means also being adapted to determine the centre of gravity of the component and lifting frame from the output signals of the means to measure the tension and the means to determine the position of the lifting point relative to the lifting frame, the processor means further being adapted to move the .lifting point of the lifting frame such that the lifting point is above the centre of gravity of the component and the lifting frame to maintain the component horizontal.

Preferably the lifting frame comprises a gantry mounted on and movable in the first direction on the lifting frame, a carriage mounted on and movable in the second direction on the gantry, the lifting point being on the carriage.

Preferably the lifting frame has at least one track and the gantry has wheels arranged to run on the at least one track. Preferably the lifting frame has a pair of parallel tracks.

Preferably the gantry has at least one track and the carriage has wheels arranged to run on the at least one track. Preferably the gantry has a pair of parallel tracks.

Preferably a force transducer measures the tension.

Preferably accelerometers detect unequal lift applied by the lifting frame to the sides of the component which causes tilting of the component.

Alternatively light sources and light detectors may measure an angle formed between the means attaching the lifting point to the crane hoist and the vertical direction to detect unequal lift applied by the lifting frame to the sides of the component which causes tilting of the component.

Preferably a motor driven power screw is arranged to move the gantry relative to the lifting frame and a motor driven power screw is arranged to move the carriage relative to the gantry.

The present invention also provides a crane comprising a crane hoist, a lifting frame having a lifting point, means to removably attach the lifting point to the crane hoist, means to removably attach the lifting frame to a component to be lifted, means to move the lifting point in a first direction on the lifting frame and means to move the lifting point in a second direction, transverse, to the second direction on the lifting frame, the lifting frame has means to measure the tension in the means attaching the lifting point to the crane hoist, the means to measure the tension being arranged to produce an output signal which is supplied to processor means, the lifting frame has means to determine the position of the lifting point relative to the frame, the means to determine the position of the lifting being arranged to supply an output signal to the processor, the lifting frame has means to detect unequal lift applied by the lifting frame to the sides of the component, which unequal lift causes tilting of the component, the means to detect unequal lift being arranged to produce an output signal which is supplied to the processor means, the processor means being arranged to stop lifting of the component to minimise the angle of tilt to ensure the component remains in contact with a surface, the processor means also being adapted to determine the centre of gravity of the component and lifting frame from the output signals of the means to measure the tension and the means to determine the position of the lifting point relative to the lifting frame, the processor means further being adapted to move the lifting point of the lifting frame such that the lifting point is above the centre of gravity of the component and the lifting frame to maintain the component horizontal.

The present invention will be more fully described by way of example with reference to the accompanying drawings in which:

Figure 1 shows a crane having a lifting frame according to the present invention.

Figure 2 shows a diagrammatic view of the lifting frame. A crane 10 has a sling 12 which carries a hook 14. A component 16 to be lifted is attached to the hook 14 via a lifting frame 18. The lifting frame 18 includes a gantry 20 which is mounted on and movable in a first direction on the lifting frame 18. The lifting frame also includes a carriage 22 which is mounted on and movable in a second direction, transverse with respect to the first direction, on the gantry 20. The carriage 22 has a lifting point 23 and the crane hook 14 is removably attached to the lifting point 23 by a shackle 24. The lifting frame 18 is removably attached to the component 16 by a plurality of suitable attaching means 26, for example bolts, slings etc. The lifting frame 18 comprises a load carrying structure formed by a first pair of parallel beams 28 and a second pair of parallel beams 29 which extend between and are secured to the first pair of beams 28. The lifting frame 18 also comprises a third pair of parallel beams 30 and a fourth pair of parallel beams 31 which extend between and are secured to the third pair of beams 30. The third pair of beams 30 are arranged to extend parallel to the first pair of beams 28, and the third pair of beams 30 are secured to, and are spaced from, the first pair of beams 28. The first pair of beams 28 and the third pair of beams 30 are I section joists, although other suitable joists may be used. The third pair of parallel beams 30 have tracks 32 on suitable surfaces, in this example the uppermost surfaces, to allow movement of the gantry 20 relative to the lifting frame 18 in a direction parallel to the first pair of parallel beams 28.

The gantry 20 comprises a load carrying structure formed by a first pair of parallel beams 34 and a second pair of parallel beams 35 which extend between and are secured to the first pair of parallel beams 34. The gantry 20 also comprises a third pair of parallel beams 36 and a fourth pair of parallel beams 37 which extend between and are secured to the third pair of beams 36. The third pair of beams 36 are arranged to extend parallel to the first pair of beams 34, and the third pair of beams 36 are secured to, and are spaced from, the first pair of beams 34. The first pair of beams 34 and the third pair of beams 36 are I section joists, although other suitable joists may be used. The third pair of parallel beams 36 have tracks 38 on suitable surfaces, in this example the uppermost surfaces, to allow movement of the carriage 22 relative to the gantry 20 in a direction parallel to the first pair of beams 34. It is to be noted that the first pair of beams 34 of the gantry 20 are arranged to extend perpendicular to the first pair of beams 28 of the lifting frame 18.

The fourth pair of beams 37 of the gantry 20 have wheels 40 rotatably mounted thereon, and the wheels 40 are arranged to run on the tracks 32 on the third pair of beams 30 of the lifting frame 18. A first power screw 42 extends parallel to the first pair of beams 28 of the lifting frame 18 and the first power screw 42 passes through threaded structure on one of the fourth pair of beams 37 of the gantry 20. One end of the first power screw 42 is driven by a stepper motor 44 in order to move the gantry 20 relative to the lifting frame 18.

The upper surfaces of portions of the load carrying structure of the gantry 20 are arranged in sliding abutment with the lower surfaces of the first beams 28 of the lifting frame 18 in order to transmit loads between the gantry 20 and the lifting frame 18. In this example the upper surfaces of the ends of the first beams 34 and the second beams 35 of the gantry 20 are in sliding abutment with the lower surfaces of the first beams 28 of the lifting frame 18.

The carriage 22 has wheels 46 rotatably mounted thereon and the wheels 46 are arranged to run on the tracks 38 on the third pair of beams 36 of the gantry 20. A second power screw 48 extends parallel to the first pair of beams 34 of the gantry 20 and the second power screw 48 passes through threaded structure on the carriage 22. One end of the power screw 48 is driven by a stepper motor 50 in order to move the carriage 22 relative to the gantry 20. The upper surfaces of the carriage 22 are arranged in sliding abutment with the lower surfaces of the first beams 34 of the gantry 20 in order to transmit loads between the carriage 22 and the gantry 20.

A force transducer 52 is positioned in the shackle 24 to measure the force, or tension, at the lifting point 23 which is attached to the crane hook 14 by the shackle 24. The force transducer 52 in this example is a load cell. The force transducer 52 produces an output signal which is supplied to a processor 56 via electrical connection 54.

A pair of accelerometers 58, 60 are mounted on the lifting frame 18 at diametrically opposite corners to detect unequal lift applied by the lifting frame 18 to the sides of the component 16 which cause tilting of the component 16 from the horizontal. The accelerometers 58, 60 produce output signals which are supplied to the processor 56 via electrical connections 62 and 64 respectively. The accelerometers have to be sufficiently sensitive to register the first movements of the lifting frame. A rotary encoder 66 on the end of the power screw 42 monitors the position of the gantry 20 relative to the lifting frame 18 and a rotary encoder 70 on the end of the power screw 48 monitors the position of the carriage 22 relative to the gantry 20. The rotary encoders 66 and 70 produce output signals which are supplied to the processor 56 via electrical connections 68 and 72 respectively.

A pair of microswitches, not shown, are arranged at the ends of one of the tracks 32 on the lifting frame 18 to ensure that the gantry 20 does not run into the lifting frame 18 and a pair of microswitches, not shown, are arranged at the ends of one of the tracks 38 on the gantry 20 to ensure that the carriage 22 does not run into the gantry 20.

A datum switch 80 is provided at a datum point at one end of track 32 and a datum switch 82 is provided at a datum point at one end of track 38.

Encoders are also provided on the crane to monitor the position of the crane, and to monitor the hoist motor on the crane.

A programmable input pad 74 is electrically connected to the processor 56.

The processor 56 supplies signals to the stepper motors 44 and 50 via electrical connections 76 and 78 respectively.

Considering Figure 2 which shows a hypothetical component with the lifting beam shown diagrammatically. The component 16 and lifting frame 18 have a centre of gravity CG, the mass of the component and lifting frame are considered to be acting at this point.

With the centre of gravity CG and the lifting point P in the position shown, the component 16 will tilt about its right hand side, as shown. The mass of the component plus lifting frame is known along with the exact position of the centre of gravity CG. The tension TS in the shackle is measured using the transducer. For the component to remain horizontal after lifting and leaving the ground then X = Dl in both X and Y directions.

Taking moments about the point of rotation of the component along the bottom of the component:-

Equation 1: TS x cos(α + θ) x [Dl - H x Tan(α + θ)] - TS x sin(α + θ) x H = m x cos θ x (X - Z x tan θ) - m x sin θ x Z for small angles -of tilt, θ, this equation can be approximated to:-

Equation 2: TS x Dl = m x X for small angles of θ as α<θ

For each component to be lifted with this lifting frame a datum position is required. The lifting frame datum has to be positioned against it. From this the length Dl will be known for both X and Y directions. TS is measured with the force transducer.

In operation the lifting frame 18 is fitted onto the component 16 by the attaching means 26. The datum 19 on the lifting frame 18 is positioned against a datum position on the component 16. At the datum position of the component 16 information relating to the mass of the component 16, and the distance of the datum position from the component edges designated to act as pivots is indicated. This information is preferably vibro-etched or may be provided on a label. The information is manually input into the processor 56 using the programmable input pad 74.

The processor 56 sends a signal to the stepper motor 44 to move the gantry 20 to the datum point on the track 32, and sends a signal to the stepper motor 50 to move the carriage 22 to the datum point on the track 38. This is to ensure that the processor 56 knows the positions of both the gantry 20 and the carriage 22.

The crane hook 14 is manually positioned directly above the lifting point 23 on the carriage 22, and the crane hook 14 is then attached to the lifting point 23 on the carriage 22 by the shackle 24. The crane hoist motor is operated to wind up the slack in the sling 12.

The crane hoist motor continues to operate and as the component 16 starts to tilt, due to unequal lift applied by the lifting frame 18 on the sides of the component 16, one of the accelerometers 58,60 sends a signal to the processor 56, which stops the crane hoist motor.

The transducer 52 measures the tension in the shackle 24. To allow for any size of component 16 it is important to ensure that the component 16 tilts at the side indicated by the datum position, whether it is in the X or Y direction first is unimportant. This is ensured by keeping the lifting point 23 to the sides of the lifting frame away from the datum 19 while establishing the position of the centre of gravity. The datum switches are thus in the diametrically opposite corner of the lifting frame to the datum point 19.

The position Dl , Dl in the x direction, is calculated by the processor 56 assuming the tilt is in the Y plane first. It is calculated by adding the distance form the datum point 19 to the pivot point on the component 16 in the X direction which has been input to the processor 56 at the programmable input pad 74, to that of the pre-stored distance from the datum switch to the datum point 19 and the distance measured by the rotary encoder between the datum switch and the carriage 22.

The processor 56 then uses equation 2 to calculate

X , X in the x direction,' Xx = TS x Dlx /'m.

The mass m is calculated by adding the mass of the component 16, which has been input to the processor 56, to the pre-stored mass of the lifting frame 18.

The processor 56 then sends a signal to lower the hoist a predetermined height to create a certain amount of slack in the sling 12. The processor 56 then sends a signal to the stepper motor 44 to move the gantry 20 in the Y direction to the side of the lifting frame 18 opposite to the datum position.

The hoist is again operated until the remaining accelerometer 58,60 activates the hoist to stop.

The transducer 52 measures the tension in the shackle 24.

The position Dl , Dl in the y direction, is calculated by the- processor 56 by adding the distance from the datum point 19 to the pivot point on the component 16 in the Y direction which has been input to the processor 56 at the programmable input pad 74, to that of the pre-stored distance from the datum switch to the datum point 19 and the distance measured by the rotary encoder between the datum switch and the carriage 22. The processor 56 then uses equation 2 to calculate X , X in the y direction.

The processor 56 now knows the centre of gravity of the lifting beam 18 and component 16 and sends signals to the stepper motors 44 and 50 to move the gantry 20 and carriage 22 such that the lifting point 23 on the carriage 22 is directly above the centre of gravity of the combined lifting frame 18 and component 16. This ensures there is no out of balance of moments and the component 16 may be lifted whilst it remains horizontal.

The component 16 may now be lifted off the ground and the component 16 will be maintained horizontal. Thus a lifting frame has been described which has means to automatically ensure that the component to be lifted will remain horizontal after leaving the ground.

A feature of the invention is that the centre of gravity is found directly in both the x and y directions while the component is on the ground. One edge only, at any time is lifted off the ground until the carriage is positioned directly above the centre of gravity. The distance this edge is raised from the ground is minimised by the accelerometers detecting the smallest movement and stopping the system. The component is therefore balanced/stabilised before it is lifted.

The load is transferred through the system of rollers ensuring all component loads are taken by the beam sections thus optimising loads. The load is taken through a single sling, thus orientating the component onto its resting place is not a problem.

It is possible to lift the component at any angle, not just horizontal. It may be possible to provide additional cables from the hook to the component to ensure the stability of the component if there are any sudden movements of the crane, or if there are sudden gusts of wind.

It may be possible to use light sources and light detectors, rather than the accelerometers. In such circumstances if H and Q shown in Figure 2 are known then an equation to relate α and θ can be formed. Measuring is possible using light sources at two sides of the sling 12, monitoring the X and Y directions and using photocells to measure the angle of tilt of the sling 12 relative to the vertical direction. The lifting frame of the invention is particularly suitable for use with gantry cranes or goliath cranes, but may be used with other types of cranes.

Claims

Claims : -

1. A lifting frame (18) for use between a crane (10) and a component (16) to be lifted, the lifting frame (18) comprising a lifting point (23), means (20,40,32) to move the lifting point (23) in a first direction on the lifting frame (18), means (22,46,38) to move the lifting point (23) in a second direction transverse to the first direction on the lifting frame (18), the lifting frame (18) has means (24) to removably attach the lifting point (23) to a crane hoist (14), means (26) to removably attach the lifting frame (18) to a component (16) to be lifted, characterised in that the lifting frame (18) has means (52) to measure the tension in the means (24) attaching the lifting point (23) to the crane hoist (14), the means (52) to measure the tension being arranged to produce an output signal which is supplied to processor means (56), the lifting frame (18) has means (66,70) to determine the positions of the lifting point (23) relative to the lifting frame (18), the means (66,70) to determine the position of the lifting point (23) being arranged to supply an output signal to the processor means (.56), the lifting frame (18) has means (58,60) to detect unequal lift applied by the lifting frame (18) to the sides of the component (16), which unequal lift causes tilting of the component (16), the means (58,60) to detect unequal lift being arranged to produce an output signal which is supplied to the processor means (56), the processor means (56) being arranged to stop lifting of the component (16) to minimise the angle of tilt to ensure the component (16) remains in contact with a surface, the processor means (56) also being adapted to determine the centre of gravity of the component (16) and lifting frame (18) from the output signals of the means (52) to measure the tension and the means (66,70) to determine the position of the lifting point (23) relative to the lifting frame (18), the processor means (56) further being adapted to move the lifting point (23) of the lifting frame (18) such that the lifting point (23) is above the centre of gravity (CG) of the component (16) and the lifting frame (18) to maintain the component (16) horizontal.

2. A lifting frame as claimed in claim 1 in which the lifting frame (18) comprises a gantry (20) mounted on and movable in the first direction on the lifting frame (18), a carriage (22) mounted on and movable in the second direction on the gantry (20), the lifting point (23) being on the carriage (22).

3. A lifting frame as claimed in claim 2 in which the lifting frame (18) has at least one track (32) and the gantry (20) has wheels (40) arranged to run on the at least one track (32).

4. A lifting frame as claimed in claim 3 in which the lifting frame (18) has a pair of parallel tracks (32).

5. A lifting frame (18) as claimed in claim 2, claim 3 or claim 4 in which the gantry (20) has at least one track (38) and the carriage (22) has wheels (46) arranged to run on the at least one track (38).

6. A lifting frame as claimed in claim 5 in which the gantry (20) has a pair of parallel tracks (38).

7. A lifting frame as claimed in any of claims 2 to 6 in which a motor driven power screw (42) is arranged to move the gantry (20) relative to the lifting frame (18).

8. A lifting frame as claimed in any of claims 2 to 6 in which a motor driven power screw (42) is arranged to move the carriage (22) relative to the gantry (20).

9. A lifting frame (18) as claimed in any of claims 1 to 8 in which a force transducer (52) measures the tension.

10. A lifting frame as claimed in any of claims 1 to 9 in which accelerometers (58,60) detect unequal lift applied by the lifting frame (18) to the sides of the component (16) which causes tilting of the component (16).

11. A lifting frame as claimed in any of claims 1 to 9 in which light sources and light detectors measure an angle formed between the means attaching the lifting point to the crane hoist and the vertical direction to detect unequal lift applied by the lifting frame to the sides of the component which causes tilting of the component.

12. A crane comprising a crane hoist (14), a lifting frame (18) having a lifting point (23), means (24) to removably attach the lifting point (23) to the crane hoist (14), means (26) to removably attach the lifting frame (18) to a component (16) to be lifted, means (20,40,32) to move the lifting point (23) in a first direction on the lifting frame (18), means (23,46,38) to move the lifting point (23) in a second direction, transverse to the second direction, on the lifting frame (18) characterised in that the lifting frame (18) has means (52) to measure the tension in the means (24) attaching the lifting point (23) to the crane hoist (14), the means (52) to measure the tension is arranged to produce an output signal which is supplied to processor means (56), the lifting frame (18) has means (66,70) to determine the position of the lifting point (23) relative to the lifting frame (Ϊ8), the means (66,70) to determine the position of the lifting point (23) is arranged to supply an output signal to the processor means (56), the lifting frame (18) has means (58,60) to detect unequal lift applied by the lifting frame (18) to the sides of the component (16) which causes tilting of the component (16), the means (58,60) to detect unequal lift is arranged to produce an output signal which is supplied to the processor means (56), the processor means (56) is arranged to stop lifting of the component (16) to minimise the angle of tilt to ensure the component (16) remains in contact with a surface, the processor means (56) is arranged to determine the centre of gravity (CG) of the component (16) and lifting frame (18) from the output signals of the means (52) to measure the tension and the means (66,70) to determine the position of the lifting point (23) relative to the lifting frame (18), the processor means (56) is arranged to move the lifting point (23) of the lifting frame (18) such that the lifting point (23) is above the centre of gravity (CG) of the component (16) and lifting frame (18) to maintain the component (16) horizontal.

13. A crane as claimed in claim 12 in which the lifting frame (18) comprises a gantry (20) mounted on and movable in the first direction on the lifting frame (18), a carriage (22) mounted on and movable in the second direction on the gantry (20), the lifting point (23) is on the carriage (22).

14. A crane as claimed in claim 13 in which the lifting frame (18) has at least one track (22) and the gantry

(20) has wheels (40) arranged to run on the at least one track (32).

15. A crane as claimed in claim 14 in which the lifting f ame (18) has a pair of parallel tracks (32).

16. A crane as claimed in claim 13, claim 14 or claim 15 in which the gantry (20) has at least one track (38) and the carriage (22) has wheels (46) arranged to run on the at least one track (38).

17. A crane as claimed in claim 16 in which the gantry (20) has a pair of parallel tracks (38).

18. A crane as claimed in any of claims 13 to 17 in which a motor driven power screw (42) is arranged to move the gantry (20) relative to the lifting frame (18).

19. A crane as claimed in any of claims 13 to 17 in which a motor driven power screw (48) is arranged to move the carriage (22) relative to the gantry (20).

20. A crane as claimed in any of claims 12 to 19 in which a force transducer (52) measures the tension.

21. A crane as claimed in claim 20 in which accelerometers (58,60) detect unequal lift applied by the lifting frame (18) to the sides of the component (16) which causes tilting of the component (16).

22. A method of lifting a component to maintain the component horizontal comprising attaching a lifting frame (18) to the component (16) such that a datum point (19) on the lifting frame (18) is positioned against a datum position on the component (16), the lifting frame (18) comprising a lifting point (23), means (20,40,32) to move the lifting point (23) in a first direction on the lifting frame (18), means (22,46,38) to move the lifting point (23) in a second direction, transverse to the first direction, on the lifting frame (18), determining the position of the lifting point (23) relative to the datum point (19) on the lifting frame (18), attaching the crane hoist (14) to the lifting point (23) by a sling (24), winding up slack in the sling (24), winding up the sling (24) until the component (16) starts to tilt due to unequal lift applied by the lifting frame (18) on the sides of the component (16), detecting unequal lift and stopping the winding up of the sling (24) to ensure the component (16) remains in contact with a surface, measuring the tension in the sling (24), calculating the position of the centre of gravity of the component (16) and lifting frame (18) from the known masses of the component (16) and the lifting frame (18), the tension in the sling (24) and the position of the lifting point (23), moving the lifting point (23) of the lifting frame (18) over the centre of gravity of the component (16) and lifting frame (18) and lifting the component (16) from the surface.