EP2238069A1

EP2238069A1 - Grab

Info

Publication number: EP2238069A1
Application number: EP08864616A
Authority: EP
Inventors: Kalle Pohjola
Original assignee: Rannikon Konetekniikka Oy
Current assignee: Rannikon Konetekniikka Oy
Priority date: 2007-12-20
Filing date: 2008-12-19
Publication date: 2010-10-13
Also published as: RU2010128082A; UA98190C2; FI20075945A0; WO2009080897A1; FI20075945L

Abstract

The grab according to the invention has a body (10, 34), at least two grapple sections (12) pivotally connected to the body, and actuators (50) for changing the position of the grapple sections. The grab has preferably six grapple sections, which are located symmetrically around an imaginary central axis of the grab. By using the actuators, the grapple sections can be rotated around their articulated coupling points between an opened and a closed position. The grapple sections are coupled to the body of the grab by swaged links (14). The actuator having adjustable length for changing the position of the grapple section is an actuator, which is coupled at its first end either directly or through a connecting piece to the second end of the grapple section and at its second end to the body of the grab. Preferably the actuator is a piston-cylinder actuator, such as a hydraulic cylinder. In one embodiment of the grab it has only one actuator for changing the position of the grapple sections. The body of the grab comprises a body plate (10) with a through-hole in the middle for the actuator. Attached to the second surface of the body plate there are support plates (34), which form an enclosed support structure to protect the actuator. The swaged links bearing the grapple sections are connected to the lugs (26) on the outer circumference of the first surface of the body plate.

Description

Grab

The present invention relates to a grab having a body, at least two grapple sections pivotally connected to the body, having a first end and a second end, and actuators for changing the position of the grapple sections.

Grabs are loading devices especially intended for handling loose materials, having a body, a number of grapple sections pivotally connected to the body and actuators for moving the grapple sections. The body has a suspension element by which the grab is attached to the lifting apparatus, such as a crane. The number of grapple sections may vary depending on the type and model of the grab. The smallest number of grapple sections is two. If there are more than two grapple sections, they are generally arranged symmetrically around the body in a circle. The grab can be set to an opened position in which the grapple sections are separate from each other, and to a closed position in which the grapple sections are settled against each other and define a cavity space between them. The grapple sections are moved between the opened and closed position by an actuator, which is generally either a hydraulic cylinder or a pulley-cable mechanism. When the grapple sections move to a different position, they rotate around their coupling joint.

Prior art grabs have many drawbacks. The actuators needed for moving the grap- pie sections are located outside the grab body, and may therefore become damaged during the use of the grab. In order to ensure the operating condition of the actuators, they must generally be protected by separate protective structures, which increases the manufacturing costs of the grab. The grapple sections are connected to the body by a coupling joint, which is located at one end of the grap- pie section. During use, the grapple sections are subjected to high loads in different directions, which causes stress on the coupling joint. Because of the structure of the grab, the coupling joints must often be made small, which weakens their durability and reduces the loading capacity. In particular, this concerns grabs having a plurality of grapple sections coupled symmetrically around the body in a circle.

A grab with two grapple sections is described in the reference SU 1013392 A. The grapple sections are coupled to the body of the grab by elongated connecting rods. It is an objective of the invention to provide a grab with a new kind of structure, by which the drawbacks and disadvantages related to the prior art solutions can be significantly reduced.

The objectives of the invention are achieved by a grab, which is characterized in what is set forth in the independent claims. Some preferred embodiments of the invention are presented in the dependent claims.

The grab according to the invention is a loading device especially suitable for handling loose materials, and it can be attached to a loader or lifting apparatus, such as a crane. The grab has a body, at least two grapple sections pivotally con- nected to the body, with a first end and a second end, and actuators for changing the position of the grapple sections. By using the actuators, the grapple sections can be rotated around their articulated connecting points between an opened and a closed position. In the closed position, the grapple sections form a space substantially closed at the lower part for the loose material being handled. In the opened state, the grapple sections are turned to a position in which they are separate from each other. In the grab according to the invention, the grapple sections are pivotally connected at their second end to an actuator adjusting the position of the sections and to the body of the grab from the area between the first and the second end. The coupling of the sections to the body has been implemented by swaged links. Swaged links are wide coupling elements, which provide durable and torsionally rigid coupling between the grapple section and the body. It is possible to use swaged links, because at the selected coupling point between the grapple section and the body, the structure of the grab does not limit the size of the coupling element used.

In one preferred embodiment of the grab according to the invention, the actuator for changing the position of the grapple section is an actuator with adjustable length and a first end and a second end. The actuator is coupled at its first end either directly or through a connecting piece to the second end of the grapple section and at its second end to the body of the grab. Preferably said actuator with adjustable length is a piston-cylinder actuator, such as a hydraulic cylinder.

Another preferred embodiment of the grab according to the invention has a cross connector, in which arrangement the second ends of the grapple sections are pivotally connected to the cross connector, and the cross connector is coupled to the first end of the adjustable length actuator. Preferably the grab has only one actua- tor for changing the position of the grapple sections. . In a third preferred embodiment of the grab according to the invention, the body comprises a body plate having a first surface and a second surface, a through- hole in the middle for the actuator, and support plates attached to the second surface of the plate. Preferably said support plates form an enclosed support struc- ture to protect the actuator, with a suspension hole for attaching the grab to the lifting apparatus.

In a fourth preferred embodiment of the grab according to the invention, the swaged link has two parallel suspension plates having a first end and a second end. The grapple sections have first lugs to which the first ends of the suspension plates are pivotally connected, and the first surface of the body plate has second lugs to which the second ends of the suspension plates are pivotally connected. Preferably said second lugs are disposed on the outer circumference of the body plate or in its vicinity.

In a fifth preferred embodiment of the grab according to the invention there are six grapple sections, which are located symmetrically around an imaginary central axis of the grab. The number of grapple sections may also be other than six, such as two, three, four, five or eight.,

The invention has the advantage that the stress imposed on the coupling mechanism is low, which improves the durability of the grab and increases its operating life.

In addition, the invention has the advantage that when the support of the grab is located substantially closer to the tip of the grapple section, the grapple sections are not required to have high torsional rigidity, and therefore the grapple sections generally need not have an enclosed structure. This reduces the manufacturing costs of the grab.

A special advantage of an embodiment of the invention is that only one actuator is needed in it for changing the position of the grapple sections. This means clear savings in the manufacturing costs of the device.

A special advantage of another embodiment of the invention is that the actuator for changing the position of the grapple sections is located inside the body of the apparatus, where it is protected from mechanical stress. Thus there is no need to provide separate protective structures for the actuator. In the following, the invention will be described in more detail. Reference will be made to the accompanying drawings, in which

Fig. 1 shows an example of a grab according to the invention in side elevation with the grab in the closed position,

Fig. 2 shows the grab of Fig. 1 in side elevation with the grab in an opened position,

Fig. 3 shows an example of a grab in an opened position from below, and

Fig. 4 shows an example of a grab in an opened position obliquely from below.

Fig. 1 shows an example of a grab according to the invention in side elevation. The grab has a body plate 10 shaped like a regular hexagon, under which six grapple sections 12 are attached by means of swaged links 14. The grapple sections have a curved, platelike wall 16 and a support rib attached on the outside of the wall. The shape of the walls is such that they have a maximum width in the centre part of the grapple section, and the width is reduced towards the ends of the grapple section. The support rib is permanently attached to the outer surface of the wall, preferably by welding. At the first end of the grapple section there is a tip piece 20 attached to the support rib detachably. The grapple sections are attached in a circular array so that they are located symmetrically around the imaginary central axis of the grab. The figure shows the grab in a closed position, in which the grapple sections are set against each other. The grapple sections thus define a cavity space closed at its lower part for the loose material handled by the grab.

The grapple sections are attached to the first surface of the body plate 10 facing downward by means of swaged links 14. The swaged links have two parallel, platelike suspension plates, the first suspension plate 22a and a second suspension plate 22b, which are connected to each other by a pipelike connecting rod 24. The first ends of the suspension plates are coupled to the first lugs 26 on the outer surface of the wall of the grapple section with first coupling bolts 28, and the second ends of the suspension plates are coupled to the second lugs 30 on the first surface of the body plate, near the outer circumference of the body plate with second coupling bolts 32. There are through-holes in the lugs and in the ends of the suspension plates for the coupling bolts. The mutual distance between the lugs attached to the first surface of the body plate and the outer surface of the wall of the grapple section is preferably equal, whereby the suspension plates of the swaged link are set in a substantially parallel position. The mutual distance between the suspension plates may be 0.5 to 2.0 times the length of the suspension plate, for example. Preferably, the mutual distance between the suspension plates is substantially equal to the length of the suspension plates. The swaged link is thus a substantially wider supporting part of the grapple section than a single rod. The placement of the lugs relatively far from each other has made the attachment mechanism of the grapple section a struc- ture that is highly resistant to the forces and stress imposed on it, especially torsional stress. It has been possible to place the lugs far from each other on the lower surface of the body plate 10, because their fixing point is on the outer circumference of the body plate or very close to it. Similarly, it has been possible to place the lugs fastened to the wall 16 of the grapple section far from each other, because they are attached at a suitable distance from the second end of the grapple section. At this fixing point, the wall of the grapple section is wide enough to enable attaching the lugs to it with a relatively long distance between them.

On the second surface of the body plate facing upwards there are six essentially trapezoidal support plates 34 having a base edge 36 and a top edge 38, which are parallel, and two side edges 40, which are divergent. The support plates are fastened at their base edge to the second surface of the body plate in a circular array so that together they constitute an enclosed supporting structure, which resembles a truncated pyramid. The adjacent support plates are attached to each other at their side edges. The side band of the top edge 38 of the support plates is bent to an angle so that the bent side bands form a hexagonal collar 42. Two opposite support plates have a suspension hole 44 at the collar for the coupling bolt (not shown) of the grab. The grapple sections 12 are moved between the opened and closed position with a hydraulic cylinder 50, which is placed mainly within the enclosed space defined by the support plates. The support plates protect the hy- draulic cylinder from mechanical stress coming from above and from the side direction. At the second end 51b of the hydraulic cylinder there is a coupling hole 52, which is concentric with the suspension hole 44. The second end of the hydraulic cylinder is coupled to the grab by a coupling bolt (not shown) fitted to the collar 42 of the supporting structure.

Fig. 2 shows the grab of Fig. 1 in side elevation. The figure shows the grab in an opened position, in which the grapple sections 12 are turned to a position in which they are separate from each other. Only the three grapple sections in the front are shown in the drawing, because the other three grapple sections in the back are hidden behind those in the front. The grab is in the position shown in the drawing when it is used to grab an object or loose material is grabbed into the grab. The grapple sections are brought to the opened position by moving the second ends of the grapple sections downward, whereby the grapple sections rotate around the first coupling bolts 28 going through the suspension plates of the swaged link 14 and the first lugs. Correspondingly, the grabs are brought to the closed position by moving the second ends of the grapple sections upward, whereby the grapple sec- tions rotate around the first coupling bolts to the position shown in Fig. 1. The position of the grapple sections is changed by changing the length of the hydraulic cylinder 50 inside the grab in a manner to be described later.

Fig. 3 shows the grab of Fig. 2 from the bottom. In the centre of the body plate 10 there is a round through-hole 54, to which the second ends of the support ribs 18 of the grapple sections 12 extend. In the middle of the hole there is a cross connector 56, on the outer circumference of which there is one clevis 58 for each grapple section. The clevis consists of two parallel, platelike lugs with a slot between them for receiving the second end of the support rib. At the second end of the support rib and in the lugs of the clevis there is a concentric through-hole, in which a coupling pin is fitted. Instead of a coupling pin, the coupling between the support rib and the clevis can be implemented by means of a ball joint, for example. This allows the cross connector to tilt freely in every direction, and the grapple sections can adjust their position according to the load in the grab.

In the centre of the cross connector there is a rectangular through-hole 62, to which the first end 51a of the hydraulic cylinder is fitted. The first end of the hydraulic cylinder is coupled to the cross connector by a coupling pin 64, which runs through a hole in the first end of the cylinder. There are holes (not shown in the drawing) on the sides of the through-hole 62 in the cross connector for receiving the coupling pin of the hydraulic cylinder.

Fig. 4 shows the grab of Figures 2 and 3 as seen obliquely from below. In order to show the internal structure of the grab better, one grapple section 12 has been removed from the drawing. The position of the grapple sections is changed by means of the hydraulic cylinder 50. When the grapple sections are to be moved to the opened position, the length of the hydraulic cylinder is increased by pushing the piston out from the cylinder, whereby the distance of the cross connector 56 and the second ends of the grapple sections attached to it from the body plate 10 increases. The grapple sections then rotate around the first coupling bolts 28 to become separate from each other in the opened position according to Figures 2, 3 and 4. When the grab is to be closed, the hydraulic cylinder is shortened by pulling the piston into the cylinder. The cross connector and the second ends of the grap- pie sections then move towards the body plate, and the grapple sections rotate around the first coupling bolts toward the closed position shown in Fig. 1.

The grab according to the invention also comprises means for conducting hydraulic oil to the hydraulic cylinder and for controlling the operation of the hydraulic cylinder of the control device. This is ordinary technique used in construction ma- chines, and therefore they are not shown in the figures. Instead of a hydraulic cylinder, the invention also enables the use of some other suitable actuator, by which the cross connector can be moved in relation to the body plate. It is also possible to implement the invention entirely without the cross connector by connecting one end of each grapple section separately to the body of the grab with an actuator having an adjustable length, such as a hydraulic cylinder.

Some preferred embodiments of a grab according to the invention have been described above. The invention is not limited to the solutions described above, but the inventive idea can be applied in numerous ways within the scope defined by the claims.

Claims

1. A grab having a body (10, 34), at least two grapple sections (12) pivotally connected to the body, having a first end and a second end, and actuators (50) for changing the position of the grapple sections, characterized in that the grapple sections are pivotally connected to the actuator from the second end and to the body (10) from the area between the first and the second end by a swaged link (14).

2. A grab according to Claim 1 , characterized in that said actuator (50) for changing the position of the grapple section (12) is an actuator having adjustable length (50) with a first end (51 a) and a second end (51 b), coupled at its first end directly or through a connecting piece to the second end of the grapple section (12) and at its second end to the body (10).

3. A grab according to Claim 2, characterized in that said actuator having adjustable length (50) is a piston-cylinder actuator, preferably a hydraulic cylinder.

4. A grab according to Claim 2 or 3, characterized in that it has a cross connector (56), the second ends of the grapple sections (12) are pivotally connected to the cross connector, and the cross connector is coupled to the first end (51a) of an actuator having adjustable length (50).

5. A grab according to Claim 4, characterized in that it has only one actuator (50) for changing the position of the grapple sections (12).

6. A grab according to any one of the claims 1 to 5, characterized in that the body comprises a body plate (10) having a first surface and a second surface and a through-hole (54) in the middle for the actuator (50), and support plates (34) coupled to the second surface of the body plate.

7. A grab according to Claim 6, characterized in that the support plates (34) form an enclosed support structure to protect the actuator, the support structure having a suspension hole (44) for attaching the grab to the lifting apparatus.

8. A grab according to Claim 6 or 7, characterized in that said swaged link (14) has two parallel suspension plates (22a, 22b), having a first end and a second end, and the grapple sections (12) have first lugs (26), to which the first ends of the suspension plates are pivotally connected, and on the first surface of the body plate (10) there are second lugs, to which the second ends of the suspension plates are pivotally connected.

9. A grab according to Claim 8, characterized in that said second lugs (30) are located on the outer circumference of the body plate (10) or in its vicinity.

10. A grab according to any one of the claims 1 to 9, characterized in that the grapple sections (12) have a platelike wall (16) and a support rib (18) coupled to its outer surface.

11. A grab according to any one of the claims 1 to 10, characterized in that it has six grapple sections (12), which are located symmetrically around an imagi- nary central axis of the grab.