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1. WO2010080023 - LIFTING TOOL FOR LIFTING A STACK OF CONCRETE REINFORCING MATS AND PLACING THE CONCRETE REINFORCING MATS ONE BY ONE, AND UNLOADING UNIT AS PART OF THE LIFTING TOOL

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LIFTING TOOL FOR LIFTING A STACK OF CONCRETE REINFORCING MATS AND PLACING THE CONCRETE REINFORCING MATS ONE BY ONE, AND UNLOADING UNIT AS PART OF THE LIFTING TOOL

The present invention relates to a lifting tool for lifting a stack of concrete reinforcing mats and placing the concrete reinforcing mats one by one, which can be operated by one person from one central location, wherein the lifting tool comprises a stable main frame which is constructed from tubular profile and which is provided with a number of, for instance four, lifting eyes and a number of, for instance six, independent unloading units slidable in the length.

Such a lifting tool is known. The known lifting tool is described in the Netherlands patent NL 1033294 of the same applicant. This special lifting tool has been developed to pick up a stack of concrete reinforcing mats in a single operation and to deliver these mats one by one from the bottom. Operation is carried out by one person at the lifting tool and one person in a lifting device. An operative steers the lifting tool directly above the stack by means of the steering bar. Using a lifting device this lifting tool can be lowered onto a stack of concrete reinforcing mats stacked onto each other. During the lowering the six unloading units slide over the longitudinal rods of the concrete reinforcing mats. When moved upward the six unloading units grip onto the rods of the concrete reinforcing mats. The lifting tool can now be hoisted with the concrete reinforcing mats to the location where they can be set down one by one. The advantage of this lifting tool is that the concrete reinforcing mats can be placed in more rapid and ergonomic manner with much less manpower and with fewer lifting movements.

The known lifting tool has the drawback that the functioning of the lifting tool depends on the accuracy of dimensioning of the concrete reinforcing mats. It is known that the accuracy of dimensioning of concrete reinforcing mats is not high. Nor is great accuracy required in the building industry. The concrete reinforcing mats are separated from each other in the known device by means of a separating pin in the unloading unit. The height of the separating pin can be set for each type of concrete reinforcing mat. It has been found that this method of separating the concrete reinforcing mats in the unloading unit of the known lifting tool is readily affected by differences in thickness of the transverse rods of the concrete reinforcing mat, whereby the concrete reinforcing mats are not unloaded properly from the unloading units.

The invention has for its object to provide a lifting tool of the type stated in the preamble which does not have the above stated drawback. The invention provides for this purpose a lifting tool of the type stated in the preamble, characterized in that each unloading unit is provided with a first set of jaws of two inner jaws intended to engage the lowest or the lowest but one concrete reinforcing mat, and a second set of jaws of four outer jaws intended to engage the lowest concrete reinforcing mat, wherein the underside of the first set of jaws is situated above the underside of the second set of jaws, and each set of jaws is adapted to perform a scissor movement between an open and closed position, and the first set of jaws and second set of jaws co-act by means of a lever construction and are coupled to each other via a bellows cylinder such that in the loading position of the lifting tool the unloading unit is pressed through the transverse rods of the successive concrete reinforcing mats, wherein the second set of jaws is situated in an open position and the first set of jaws opens as it passes over each transverse rod and, after passing over each transverse rod, closes due to its own weight, that in the lifting position of the lifting tool the first set of jaws closes under the lowest reinforcing mat due to the weight of the stack of reinforcing mats, upon first operation of the lifting tool the second set of jaws closes and the first set of jaws opens such that the lowest reinforcing mat drops out of the first set of jaws into the second set of jaws, and upon second operation of the lifting tool the first set of jaws closes and the second set of jaws opens such that the lowest reinforcing mat drops out of the unloading unit

Due to the use of an inner jaw and an outer jaw the unloading unit has been found to be much less readily affected by differences in the thickness of the concrete reinforcing mat. The inner jaw and outer jaw engage under the concrete reinforcing mat, while in the known device the transverse rod of the concrete reinforcing mat must fit into a space defined by a drop pin and a separating pin. Through use of the lever construction the stack of concrete reinforcing mats is always clamped by the first set or second set of jaws in the mode of use of the lifting tool. In a first preferred embodiment of the lifting tool according to the invention the first and second set of jaws are provided with a shared pivot point. The lever construction can be further simplified by applying a shared pivot point.

In a second preferred embodiment of the lifting tool according to the invention the second set of jaws is connected by means of draw springs to the lever construction such that in the loading position of the lifting tool the second set of jaws opens. The second set of jaws is in this way biased in an advantageous manner.

In a third preferred embodiment of the lifting tool according to the invention the stroke of the second set of jaws is adjustable by means of an arresting pin which co-acts with stroke limiting profiles. The stroke limiting can in this way be set in simple manner. In a fourth preferred embodiment of the lifting tool according to the invention each inner jaw and each outer jaw are provided on the inner side of the lower part thereof with a triangular protrusion. The clamping force of the first set and the second set of jaws is in this way dependent on the weight of the stack of concrete reinforcing mats. The heavier the stack, the greater the clamping force will be. In addition, the triangular protrusion ensures a further decreased dependence on the accuracy of dimensioning of the concrete reinforcing mats.

The lifting tool can preferably be operated electrically, hydraulically or pneumatically. The lifting tool can be provided for this purpose with a hydraulic or pneumatic compressor, a power generator or a combination thereof.

The invention also relates to an unloading unit as described as part of the above described lifting tool.

The invention will be further elucidated with reference to the following figures, in which:

Figure 1 shows an overview of the lifting tool according to the invention; Figure 2 shows an overview of the unloading unit as part of the lifting tool according to the invention; Figure 3 shows a side view of the unloading unit as part of the lifting tool according to the invention in the loading position of the lifting tool;

Figures 4 and 5 show a side view of the unloading unit as part of the lifting tool according to the invention, wherein the unloading unit is hoisted upward and the lowest concrete reinforcing mat is separated from the concrete reinforcing mat lying above it;

Figures 6 and 7 show a side view of the unloading unit as part of the lifting tool according to the invention, wherein the lowest concrete reinforcing mat is released from the unloading unit.

Description and operation of the main frame: Fig. 1

The lifting unit consists of a main frame, Fig. 1 pos.1, constructed from tubular profile. On the main frame are six horizontally slidable unloading units, Fig. 1 pos. 4,7,10,11,15 and 20. The unloading units, Fig. 1 pos. 4,7,10,11,15 and 20 can slide in continuously variable manner to each pitch measure and be secured by means of a handle, Fig. 3 pos. 30.

The dimensioning of the main frame is chosen such that multiple types of concrete reinforcing mats can be loaded. The operation of the six unloading units. Fig. 1 pos. 4,7,10,11,15 and 20, takes place centrally by means of a pneumatic manual valve, Fig. 1 pos. 6. [Extendable tubes, Fig. 1 pos. 2,3,9 and 12, are arranged at four points in the frame. These tubes are provided with arresting pins. The lifting tool lies on these extendable tubes when it is not in use. The lifting frame is provided with four lifting eyes, Fig. 1 pos. 8,13,18 and 19. The lifting tool can be suspended in stable manner in the lifting device by means of a balancing assembly. A steering bar, Fig. 1 pos. 5, is mounted on one long side of the main frame. The height of the steering bar is chosen such that the operator can remain standing upright, while the mats drop out of the lifting tool at knee height. The depth of the steering bar, Fig. 1 pos. 5, is also chosen so that the protruding ends of the concrete reinforcing mats cannot come into contact with the operator when they drop. The steering bar, Fig. 1 pos. 5, can be easily folded away so that the lifting tool fits within the dimensions of a truck.

A removable pneumatic compressor, Fig. 1 pos. 16, is mounted on the main frame. A removable electric power generator, Fig. 1 pos. 14, is mounted opposite this pneumatic compressor, Fig. 1 pos. 16. This electric power generator, Fig. 1 pos. 14, provides the electric current for the pneumatic compressor, Fig. 1 pos. 16. The pneumatic compressor, Fig. 1 pos. 16, provides the six unloading units, Fig. 1 pos. 4,7,10,11,15 and 20 with compressed air. The electric power generator, Fig. 1 pos. 14, and the pneumatic compressor, Fig. 1 pos. 16, are protected by a steel casing for the purpose of theft prevention.

Description of the unloading unit: Fig. 2 An unloading unit is mounted for horizontal sliding in the main frame, Fig. 1 pos. 1 , by means of the unloading unit sub-frame, Fig. 2 pos 12. The unloading unit sub-frame can be secured to the main frame, Fig. 1 pos. 1, by means of the blocking handle Rg. 3 pos. 30.

Clamping protrusions, Fig. 3 pos. 31 and 32, ensure that the unloading unit cannot be lifted from the main frame.

Two U-profiles are placed on the unloading unit sub-frame Fig. 2 pos. 12. The unloading unit can slide vertically herein by means of the lower slide block, Fig. 2 pos. 10, and upper slide block. Fig. 2 pos. 15, this in order to be able to compensate for the height difference of a stack of concrete reinforcing mats. Two draw springs, Fig. 2 pos. 27 and 28, are placed between the lower slide block, Fig. 2 pos. 10, and upper slide block, Fig. 2 pos. 15. These two draw springs together ensure that the outer jaws, Fig. 2 pos. 1,2,3 and 26, are pulled apart on the underside in non-operated mode.

There are four outer jaws, Fig. 2 pos. 1,2,3 and 26, and two inner jaws, Fig. 2 pos. 4 and 29, per unloading unit. The inner jaws, Fig. 2 pos. 4 and 29, are mounted rotatably on the central pin, Fig. 2 pos. 5. The upper part of the inner jaws are mounted rotatably on the lower levers, Fig. 2 pos. 7,8 and 11 , by means of a pin, Fig. 2 pos. 6 and 13. The lower levers are mounted centrally on lower slide block, Fig. 2 pos. 10, for rotation via a pin, Fig. 2 pos. 9. The bellows cylinder, Fig. 2 pos. 14, is mounted on top of the lower slide block, Fig. 2 pos. 10.

The outer jaws, Fig. 2 pos. 1,2,3 and 26, are mounted in the centre for rotation on the central pin, Fig. 2 pos. 5. The upper part of the outer jaws, Fig. 2 pos. 1,2,3 and 26, are mounted rotatably on the upper levers, Fig. 2 pos. 17-20, by means of a pin, Fig. 2 pos. 21 and 24. The upper levers. Fig. 2 pos. 17-20, are mounted centrally on upper slide block, Fig. 2 pos. 15, for rotation via a pin, Fig. 2 pos. 16. The bellows cylinder, Fig. 2 pos. 14, is mounted on the underside of this upper slide block, Fig. 2 pos. 15.

On the top side of the outer jaws two stroke limiting profiles, Fig. 2 pos. 22 and 23, are mounted slidably over pin, Fig. 2 pos. 24, and rotatably about pin, Fig. 2 pos. 21.

Situated in these stroke limiting profiles, Fig. 2 pos. 22 and 23, is an arresting pin, Fig. 2 pos. 25, which limits the outward stroke of the outer jaws, Fig. 2 pos. 1,2,3 and 26. The arresting pin, Fig. 2 pos. 25, can be placed at two different positions in the holes of the stroke limiting profiles, s The stroke limitation can in this way be adjusted.

(In order to make all components visible, the outer jaw, Fig. 2 pos. 2, is omitted).

0 The operation of the unloading unit

1. Loading of the concrete reinforcing mats: Fig. 3

When the bellows cylinder, Fig. 3 pos. 14, is not operated, the outer jaws, s Fig. 2 pos. 1,2,3 and 26, are pulled toward each other on the top side by the draw springs, Fig. 2 pos. 27 and 28. This creates sufficient space on the underside for the outer jaws, Fig. 3 pos. 1,2,3 and 26, to be able to drop freely over the threaded rods of the concrete reinforcing mats.

0 When the lifting tool is lowered the inner jaws, Fig. 3 pos. 4 and 29, come to lie on the threaded rod of the uppermost concrete reinforcing mat Fig. 3 pos. 32. The inner jaws, Fig. 3 pos. 4 and 29, are pressed onto the threaded rod of the concrete reinforcing mat by the weight of the unloading unit. Owing to the angled sides on the underside of the inner jaws, Fig. 3 pos. 4 and 29, the 5 inner jaws are pressed outward by the threaded rod. Once the threaded rod has passed over the triangular protrusion of the inner jaws, the inner jaws, Fig. 3 pos. 4 and 29, once again move against each other due to their own weight. This process is repeated each time a threaded rod passes over, until the desired number of concrete reinforcing mats has been loaded. 0

2. Lifting of a number of concrete reinforcing mats: Fig. 4

When the correct depth has been reached it is possible to begin lifting the reinforcing mats. When the main frame, Rg. 1 pos. 1, is lifted, the lower slide 5 block, Fig. 2 pos. 10, slides as far as the lower stop in the unloading unit sub-frame, Fig. 3 pos. 12. From that moment the unloading unit is also lifted. The concrete reinforcing mats, Rg. 4 pos. 32, are here suspended on top of the triangular protrusions of the inner jaws, Rg. 4 pos. 4 and 29. Owing to the form of the inner jaws, Fig. 4 pos. 4 and 29, they clamp under the lowermost threaded rod of the lowest concrete reinforcing mat, Fig. 4 pos. 32, of the number of concrete reinforcing mats to be lifted. The heavier the stack, the greater this clamping force will be. The rest of the concrete reinforcing mats, Fig. 4 pos. 32, lie on top of the clamped concrete reinforcing mat and are thus also lifted.

Operation of the unloading unit.

3. Separation of the lowest concrete reinforcing mat: Fig. 4 and 5

The bellows cylinder, Fig. 4 pos. 14, is extended by operating the pneumatic valve, Fig. 1 pos. 6. The upper levers, Fig. 4 pos. 17-20, hereby press the outer jaws, Fig. 4 pos. 1 ,2,3 and 26, outward on the top side. The outer jaws, Fig. 4 pos. 1,2,3 and 26, hereby close on the underside. This stroke is limited by the arresting pin, Fig. 4 pos. 25, which protrudes into the stroke limiting profiles, Fig. 4 pos. 22 and 23. As soon as the outer jaws, Fig. 4 pos. 1,2,3 and 26, make contact with each other on the underside, the clamping force transfers from the inner jaws, Fig. 4 pos. 4 and 29, to the outer jaws, Fig. 4 pos. 1,2,3 and 26. The inner jaws, Rg. 5 pos. 4 and 29, are hereby opened. The whole stack of concrete reinforcing mats, Fig. 5 pos. 32, to be lifted drops out of the inner jaws, Fig. 5 pos.4 and 29, and comes to lie in the closed outer jaws, Fig. 5 pos. 1,2,3 and 26. The dropping distance can be set by means of the arresting pin, Fig. 5 pos. 25, in the stroke limiting profiles, Fig. 5 pos. 22 and 23.

4. Release of the lower concrete reinforcing mat: Fig. 6 and 7

By once again operating the pneumatic valve, Fig. 1 pos. 6, the bellows cylinder, Fig. 6 pos. 14, is retracted. The clamping force is hereby returned from the outer jaws, Fig. 6 pos. 1,2,3 and 26, to the inner jaws, Fig. 6 pos. 4 and 29. Owing to the form of the inner jaws and the correct position of the arresting pin, Fig. 6 pos. 25, in the correct hole of the stroke limiting profiles, Fig. 6 pos. 22 and 23, the inner jaws, Fig. 4 pos. 4 and 29, come together precisely below the lowest but two of the threaded rods. Only when this clamping force has been fully transferred will the outer jaws. Fig. 7 pos. 1,2,3 and 26, move open. The lowest concrete reinforcing mat, Fig. 7 pos. 32, hereby drops out of the unloading unit. The rest of the concrete reinforcing mats to be lifted, Fig. 7 pos. 32, remain clamped by the inner jaws, Fig. 7 pos. 4 and 29.

By once again operating the pneumatic valve, Fig. 1 pos. 6, the following concrete reinforcing mat is separated from the stack, and so on.

The whole stack of concrete reinforcing mats, Fig. 7 pos. 32, is in this way delivered one by one.