GB2285965A

GB2285965A - Grab device

Info

Publication number: GB2285965A
Application number: GB9424000A
Authority: GB
Inventors: Wolfgang Sachs
Original assignee: Kinshofer Greiftechnik GmbH
Current assignee: Kinshofer GmbH
Priority date: 1994-01-29
Filing date: 1994-11-28
Publication date: 1995-08-02
Anticipated expiration: 2014-11-28
Also published as: IT1271780B; FR2715645A1; JPH07257874A; FR2715645B3; DE4402641C1; ITMI942597A1; JP2696681B2; ITMI942597A0; GB9424000D0; GB2285965B

Abstract

The invention relates to a gripping device with gripping arms (2), which are mounted so as to be displaceable parallel to one another in a supporting piece (7), provided with a suspension device, via two legs (6) each connected to the gripping arms (2) at an angle, and at least one linear drive, preferably a hydraulic piston/cylinder unit (15), moving the gripping arms (2) towards one another and away from one another. The piston/cylinder unit (15) preferably consists of two cylinders (16) arranged essentially parallel to one another and connected to the supporting piece (7). The piston rods (17) of the cylinders (16) are linked to the gripping arms (2), preferably to cross pieces (4) serving as a stop. A gripping device (1) with as uniform a contact pressure of the gripping arms (2) as possible, which is inexpensive to manufacture and is easy to maintain in a simple and inexpensive manner and in particular permits easy and quick exchange of certain components, in particular the drive units, and at the same time fulfils the requirements of the regulations for prevention of accidents, is created by the cylinder or cylinders (16) of the piston/cylinder unit (15) being mounted in their centre area, the mounting (18) being an integral part of the supporting piece (7) and permitting a limited pivoting action of the cylinder or cylinders (16) about their radial axis. <IMAGE>

Description

1 Grab Device 2285965 This invention relates to a grab device and

preferably to one for a stack of stone, said grab device comprising grab arms which are mutually parallel displacably supported in a carrying piece provided with coupling means through two legs angularly connected to said grab arms, and comprising at least one linear driving means for moving said grab arms toward and away from each other, said driving means preferably being a hydraulic piston-cyfinder unit which preferably consists of two mutually parallel cylinders connected to the carrying piece, the piston rods of said cylinders being coupled to the grab arms and preferably to cross arms serving as a stopper.

Such grab devices are known from prior art. From document DE-GM 92 04 627. 4, for example, a grab of this type is known, preferably one for a stack of stone, wherein the grab arms are substantially L-shaped, thus having two angularly interconnected legs of which two legs of each grab arm are displacably supported in a carrying piece such that the distance between the grab arms may be varied in order to clamp, for example, a broad and preferably a cuboid stack of stone between the grab arms. A stack of stone clamped in this manner may be moved, for example, between two positions. Consequently, such grabs are preferably used on loading cranes of trucks, the stacks of stone being either loaded to or unloaded from the truck by means of said grab. However, it is also conceivable to use such a grab for other purposes such as packaging process if in the course thereof substantially broad articles or piles of articles are to be transferred or displaced from one point to another. Accordingly, such grabs can be used, for example, also on hall cranes.

To effect the movement of the grab arms, the grab known from the abovementioned utility model comprises a hydraulic piston-cylinder unit consisting of two cylinders connected to the carrying piece, the piston rods of the piston-cylinder unit being coupled to the cross arms which interconnect two legs of a grab arm. Thus the grab arms are moved toward and away from each other by means of said hydraulic piston-cylinder unit. With this known grab it can be recognised that the cylinders at their ends averted from the piston rod are coupled to holding members which are connected to the carrying piece.

Moreover, from document DE-OS 41 38 648 a grab for a stack of stone is known which essentially corresponds to the above-described grab, the difference between these two known grabs residing in the arrangement of the legs of each grab arm. With the grab known from the aforementioned utility model the legs of each grab arm are equally spaced from each other and, being parallel offset, are guided in guides of the carrying piece in a manner such that the legs of said one grab arm lie on sides of the leg of the other grab arm which point in the same direction, whereas the stone grab according to document DE-OS 41 38 648 includes two grab arms which legs have a different distance to each other so that the legs of said one grab arm are arranged between the legs of the opposing other grab arm.

The above-described grabs andlor stone grabs have proven to be expedient mainly for the aforementioned tasks.

Basing on this prior art, it is an o b j e c t of the invention to provide a grab device of the type concerned which contact pressure is as uniform as possible, which is easy to manufacture, simple and inexpensive in its maintenance and allows components thereof, especially the driving units, to be replaced easily and quickly, while meeting the requirements of accident prevention.

Still further, a grab device is to be provided which comes in a simple modular form.

The s o 1 u t i o n of this problem provides that the cylinder(s) of the pistoncylinder unit is(are) supported in its(their) central portion, said support being part of the carrying piece and allowing limited slewability of the cylinder(s) about its(their) radial axis.

A particular advantage obtained by said limited slewability of the cylinder(s) is that the contact pressure applied against an article to be grabbed, e.g. a stack of stone, is as uniform as possible. A further advantage of the device according to the invention is that by supporting the cylinder(s) in its(their) central portion a driving arrangement can be realised in this type of a grab It device which is easy to manufacture and simple as well as inexpensive in its maintenance. This construction especially allows for easy and quick exchanging of these components.

According to a further feature of the invention it is provided that the cylinder is supported in a supporting construction consisting of at least one holding member connected to said cylinder, a holding member connected to the carrying piece and a bearing member arranged between the holding members and enabling slewability. It can be seen that the fixing of the cylinder(s) in the above-described manner is especially simple because only one holding member each is to be provided in the regions of the cylinder and the holding member, the bearing member being located between said holding members and being formed so that the cyiinder(s) is(are) supported on the bearing member such that it may be swivelled to a limited extent. In addition, this construction allows for simple setting of a defined slewability of the cylinders.

With the above-described embodiment of the grab device according to the invention it is further provided that between the cylinder holding member and the holding member of the carrying piece formed as a central web a ring is arranged which supports the bearing member and preferably is in the form of a ball socket ring. Such construction of the grab device according to the invention provides in a simple manner for the bearing member being safely seated on one hand and for improved slewability of the cylinder or cylinders relative to the carrying piece on the other hand.

It will be particularly advantageous if the ring andlor the bearing member consist of a hardened material, preferably of hardened steel, thus avoiding or considerably reducing wear caused by the swivelling motion of the cylinders relative to the carrying piece within the zone of the ring supporting the bearing member. A simple construction of the grab device according to the invention, which especially allows advantageous swivelling of the cylinder or cylinders relative to the carrying piece, is obtained by the ring having a spherical surface co-operating with a surface of the bearing member which is also formed as a spherical surface. On this spherical surface of the ring the bearing member can be movably guided in a simple manner. Preferably, the ring is rigidly connected to the holding member of the carrying piece. This results in that the holding member of the carrying piece can be easily and inexpensively manufactured along with the ring on one side and in that the ring is arranged at a predetermined location already at the time of manufacturing of the grab device according to the invention on the other side. Furthermore, any wear of the holding member of the carrying piece caused by friction between the ring and the holding member of the carrying piece is avoided thereby. Finally, this construction offers the advantage that the ring is captivated to the cylinder so that the ring will neither get lost nor will be damaged during maintenance work. However, it is also possible to detachably mount the ring to the holding member of the carrying piece (central web), for example, by clamping the ring onto the holding member of the carrying piece or by a screwed connection thereto.

It has proven to be a particular advantage if the cylinder holding member is formed as a ring support having an L-shaped cross section, a bearing member receiver being provided between the legs of the ring support which are arranged substantially at right angles to each other. Namely, this embodiment provides for the advantage of the bearing member to be easily arranged at a predetermined location prior to connecting the cylinder holding member to the holding member of the carrying piece, for example.

Moreover, it is expedient to form the bearing member with a substantially triangular cross section, the triangular shape preferably being approximately right-angled and the catheti lying against the legs of the ring support and the hypotenuse lying against the spherical surface of the ring. By this construction of the grab device according to the invention the advantage is obtained that the bearing member contacts the spherical surface of the ring through a contact surface which is as large as possible so that surface pressure in this area is relatively small compared to other constructions of the bearing member.

The connection between the cylinder holding member and the carrying piece member is preferably effected by means of a bearing cover screwed to the ring which is formed as a ball socket ring, the cylinder holding member being preferably clamped to the central web. Moreover, by this ball socket ring the advantage is obtained that the space between the cylinder holding member and the carrying piece member, in which the bearing member and the ring are arranged, is almost completely closed so that any excessive penetration of dirt particles and other foreign material is avoided in a simple and inexpensive way.

A0 n It has shown to be a particular advantage if between the bearing cover and the ring a push-on ring is provided consisting of an elastomer, said push-on ring enabling slewability of the cylinder or cylinders within 20 to 40 and preferably 30. To this end it will be especially advantageous if the hardness of the elastomer is less than 75 shore and preferably between 30 and 40 shore. The above-mentioned features of the grab device according to invention provide for the desired contact pressure of the grab arms, which is to be as uniform as possible, on one hand and for a simple and inexpensive support of the cylinder or cylinders on the other hand.

A further improvement of the grab device according to the invention in respect of easy and quick exchanging of certain components, especially of the driving units, is obtained by the carrying piece consisting of a holding device arranged between two guiding members guiding the legs of the grab arms, said holding device having at least one central web and being detachably connected to the guide members. Preferably, said holding device is screwed to the guide members. By this construction there is obtained the advantage that the centrally arranged carrying piece may be easily and quickly removed from and thus exchanged in the grab device according to the invention. Maintenance of the driving units, namely of the piston-cylinder unit, is therefore possible in the works of the manufacturer without the entire grab device being available for this purpose. In addition, this construction helps to considerably reduce maintenance cost for such grab devices because it only requires the carrying piece with the piston-cylinder unit to be dismounted and replaced. Accordingly, the remaining components of the grab device can be combined with a new piston-cylinder unit as well as an associated carrying piece. Finally, the above-described embodiment of the grab device according to the invention has the advantage that such carrying pieces with piston-cyiinder units can be combined with differently designed grab arms in a modular form. This results in considerable advantages at the manufacturing of such grab devices, since, for example, only a single carrying piece with a particular type of piston-cylinder unit is to be kept available for various grab devices.

Simple construction of the grab device according to the invention is attained by the holding device being formed as a cross arm having connecting sheet metal plates on its ends to which the guide members can be fixed, preferably by a screwed connection. However, it is also conceivable that on the holding device, which is formed as a cross arm, U-shaped receivers are provided embracing the guide members and being screwed to them. This construction offers the advantage of improved stability of the grab device according to the invention, especially in the connecting portion between the carrying piece and the grab arms.

The guide members preferably consist of a guiding part and bilaterally arranged cast parts which are respectively formed as tubular components having a substantially rectangular and preferably square cross section. Here it has shown to be particularly advantageous if each guiding part in its central portion has a guide pin extending parallel to the grab arms and arranged between the legs of two opposing grab arms. By means of said guide pin the legs of the opposite grab arms which are guided past each other are guided in a manner such as to avoid tilting of the legs in the guiding part. In addition, friction between the legs of the grab arms which are guided past each other is reduced to a minimum, since the legs are not moved lying on top of each other.

A further improvement of the guiding of the legs is attained by at least one guiding web respectively being arranged in the cast parts. Preferably, each guiding part has one guiding web in each cast part so that the guiding of the legs of opposing grab arms guided past each other is effected in each guiding part through the guide pin and the two guiding webs provided in the cast parts. The guide pins together with sliding bearings are screwed to the cast part.

The cast parts are preferably screwed to the guiding parts so that at the manufacturing of the grab device according to the invention the number of those components is reduced which are to be combined in the final stage of mounting.

Furthermore, it has shown to be an advantage if the bearings for guiding the legs of the grab arms are embedded in the cast parts, said bearings preferably consisting of a bearing body having a sliding surface. To this end, bearing receivers are embedded in the cast parts and corresponding bearings are screwed into them so that the bearing surfaces ride on the upper and lower sides of the grab arm sleepers. The sliding surfaces of the bearing 7 bodies are disposed so as to rest on the inner surfaces of the guiding part and have a friction-reducing effect.

With the grab device according to the invention it is finally provided that at least one cylinder of the piston-cylinder unit has a manometer in its bottom face for indicating the clamping pressure as a value representative of the carrying capacity of the grab arms. It is a particular advantage of this embodiment that the manometer is directly connected to the cylinder of the piston-cylinder unit so that any cables can be omitted which, for example, could be damaged or destroyed while working with a grab device of this type which may lead to stop periods of the grab device. In addition, by the manometer being arranged in the bottom portion of the cylinder the manometer itself and especially its show glass are protected from being damaged.

Further features and advantages of the present invention become apparent from the following description of a preferred embodiment with reference to the accompanying drawings wherein it is shown in:

Figure 1 a perspective side view of a grab device; Figure 2 a top view of the grab device according to Figure 1; Figure 3 a side view of the grab device according to Figures 1 and 2; Figure 4 a representation of a part of a carrying piece with a piston-cylinder unit of the grab device according to Figures 1 to 3; Figure 5 a side view of the carrying piece according to Figure 4 along line A-A in Figure 4; Figure 6 a top view of the carrying piece according to Figures 4 and 5 along line B-B in Figure 4, and Figure 7 an enlarged side view of the connection of the carrying piece to the piston-cylinder unit according to Figures 4 to 6.

A grab device as shown in Figures 1 to 3 is formed as a grab 1 for a stack of stone and consists of two L-shaped grab arms 2, each having two supports 3 and legs 6, respectively. The supports 3 of each grab arm 2 are interconnected through two cross arms 4 and 5 so as to be spaced from each other. Accordingly, each grab arm 2 has two legs 6 angularly connected to the supports 3, said legs being mutually parallel displacabiy supported in a carrying piece 7 so that the grab arms 2 can be moved toward and away from each other.

The carrying piece 7 consists of a holding device 8 which is arranged between two guide members 9 guiding the legs 6 of the grab arms 2, said holding device 8 being screwed to the guide members 9. As can be seen especially from Figures 1 and 3, the holding device 8 is in the form of a cross arm provided on the free ends thereof with connecting. sheet metal plates 10 to which said guide members 9 are fixed by a screwed,connection.

The guide members 9 consist of a central guiding part 11 and cast parts 12 respectively provided on its both sides. The guiding parts 11 and cast parts 12 are formed as tubular components having a substantially rectangular cross section.

In its central portion each guiding part 11 has a guide pin 13 extending parallel to the grab arms 2 and being disposed between the legs 6 of two opposing grab arms 2.

Furthermore, in each cast part 12 a guiding web is arranged which also engages between the two legs 6 of two opposing grab arms 2 and guides the same. Accordingly, between two legs 6 of two opposing grab arms 2 three guiding components are arranged, namely said guide pin 13 and two guiding webs locating inwardly of said guide members 9.

1 7.

-g- In the embodiment as shown, the cast parts 12 are welded to the guiding parts 11, bearings 14 for guiding and supporting legs 6 of the grab arms 2 being screwed into the cast parts 12.

As can be further seen from Figures 1 and 2, the stone grab 1 has a hydraulic piston-cylinder unit 15 consisting of two substantially mutually parallel cylinders 16 connected to the carrying piece 7, the piston rods 17 thereof being coupled to the cross arms 4 of the grab arms 2. The cylinders 16 of the piston-cylinder unit 15 are supported in their central portion, the bearing application 18 being described later in more detail with reference to Figures 4 to 7. The bearing application 18 is part of the carrying piece 7 and allows for limited slewability of the cylinders 16 about their radial axes.

In Figures 4 to 7, the connection between the piston-cylinder unit 15 and the carrying piece 7 is shown. As can be seen in Figure 4, the carrying piece has two mutually parallel plates 19 and 20 between which the cylinders 16 are arranged. To this end, the carrying piece 7 has at least one central web 21 which is arranged at right angles between the plates 19 and 20 and is welded thereto. The central web 21 is also formed as a plate-shaped member and has two circular openings of a diameter which is slightly superior to the external diameter of each cylinder 16. Accordingly, the central web 21 represents a holding member for the carrying piece which is welded to the carrying piece 7 and connected to the cylinder 16.

Coaxially with the opening for the cylinder 16 a ring 22 of hardened steel is welded on the central web 21. The ring 22 has a spherical surface 23 and may be pushed on or, as an alternative, screwed to the central web 21.

In the central portion of the cylinder 16 an annular cylinder holding member 24 having an L-shaped cross section is welded to the outer surface of the cylinder 16. Accordingly, the cylinder holding member 24 is formed as a ring support, the cylinder holding member 24 having two legs arranged substantially at right angles to each other, one of which resting on the outer surface of the cylinder 16 and being welded thereto. The second leg of the cylinder holding member 24 accordingly stands radially on the cylinder and together with the first leg forms a receiver for a bearing member 25 which is essentially triangular in cross section, the triangular shape being approximately right-angled and the catheti lying against the legs of the cylinder holding member 24 and the hypotenuse, which is formed as a spherical surface, lying against the spherical surface 23 of the ring 22. Consequently, the spherical surface 23 co-operates with a spherical surface of the bearing member 25, the bearing member 25 enabling slewability of the cylinder 16.

Finally, a bearing cover 27 is screwed to the ring 22, with a push-on ring 26 being interposed, clamping the cylinder holding member 24 to the ring 22. The push-on ring 26 consists of an elastomer and rests on the outer surface of the radially extending leg of the cylinder holding member 24, pressing the same onto the bearing member 25, whereby sufficient surface pressure is produced between the spherical surface of the bearing member 25 and the spherical surface 23 of the ring 22 so that the cylinder 15 is sufficiently supported in the central web 21 in order to transmit reaction forces to the carrying piece 7 upon operation of the grab arms 2.

Especially in Figure 7 it can be seen that the bearing cover 27 is connected to the ring 22 by means of screws 28 resulting in that the bearing cover 27 can be easily dismounted. This provides for the cylinder 16 to be detached from the carrying piece 7 in a simple manner.

In Figures 5 and 6 slewability of the cylinder 16 is shown by arrows 29 represented in segments of a circle, the angle of slewability of the cylinder being 30 both in the motional direction shown in Figure 5 and in that shown in Figure 6. The push-on ring 26 consists of an elastomer having a hardness between 20 and 40 shore.

Finally, in Figures 5 and 6 reference number 30 designates the main traction force "closing" and reference number 31 the main traction force "opening".

From the above description it may be learnt that by virtue of the slewability of the cylinder 16 in the central web 21 the grab device according to the invention in a simple manner provides for a contact pressure applied by the grab arms 2 to an object to be grabbed which is as uniform as possible. In addition, the above-described stone grab is devised such that the carrying piece 7 with the piston-cylinder unit 15 can be easily detached from the stone grab 1 by unscrewing the carrying piece 7 from the guide members 9 in the portion of the connecting sheet metal plates 10 and by removing the piston rods 17 from the cross arms 4, whereupon the carrying piece 7 with the piston-

7 cylinder unit 15 can be lifted off the stone grab 1. Thereafter, the cylinders 16 can be easily detached from the carrying piece 7 by loosening the screws 28 and thereafter pulling the bearing covers 27 off the ring 22. Then the cylinders 16 can be withdrawn from the corresponding openings in the central web 21 of the carrying piece 7.

As can be seen in Figures 1 and 3, at least one cylinder 16 is provided with a manometer 32 indicating the clamping pressure of the grab arms 2. This manometer 32 is inserted in the bottom face of the cylinder 16 such that any exposed connection members such as hydraulic hoses liable to be damaged or destroyed during operation of the stone grab 1 do not exist between the cylinder 16 and the manometer 32. In addition, danger of destruction of the manometer 32, for example, by its breaking off is considerably reduced.

On closing the grab arms 2 movability of the cylinder 16 is attained by the spherical surfaces of the ring 22 and the bearing member 25 sliding on top of each other. Both the bearing member 25 and ring 22 consist of hardened steel in order to reduce wear. On opening the grab arms 2 the cylinder holding member 24 takes support on a rubber ring, thereby enabling the required movability of the cylinder 16. Through the construction of the two spherical surfaces of the ring 22 and bearing member 25 a uniform contact pressure is obtained of the grab arms 2.

List of Reference Numerals 1 2 3 4 5 6 7 8 9 11 12 13 14 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 stone grab grab arm support cross arm cross arm leg carrying piece holding device guide member connecting sheet metal plate guiding part cast part guide pin bearing piston-cylinder unit cylinder piston rod bearing application plate plate central web ring spherical surface cylinder holding member bearing member push-on ring bearing cover screw arrow arrow arrow manometer 31

Claims

1. A grab device, preferably one for a stack of stone, comprising grab arms mutually parallel displacably supported in a carrying piece provided with coupling means through two legs, respectively angularly connected to said grab arms, and comprising at least one linear driving means, preferably a hydraulic piston-cylinder unit, for moving the grab arms toward and away from each other, said driving means preferably consisting of two substantially parallel cylinders connected to said carrying piece, the piston rods thereof being coupled to the grab arms, preferably to cross arms serving as a stopper, characterised in that the cytinder(s) (16) is(are) supported in its(their) central portion, the bearing application (18) being part of the carrying piece (7) and enabling limited slewability of the cylinder(s) (16) about its(their) radial axis.

2. A grab device according to claim 1, characterised in that the cylinder(s) (16) is(are) supported in a holding device consisting of at least one holding member (24) connected to the cylinder (16), a holding member (21) connected to the carrying piece (7), and a bearing member (25) disposed between the holding members (21,24) and enabling slewability.

3. A grab device according to claim 2, characterised in that between the cylinder holding member (24) and the central web (21) a ring (22) is arranged which supports the bearing member (25) and is preferably in the form of a ball socket ring.

4. A grab device according to claim 3, characterised in that the ring (22) andlor the bearing member (25) consist of a hardened material, preferably of hardened steel.

5. A grab device according to claim 3 or claim 4, characterised in that the ring (22) has a spherical surface (23) which co-operates with a surface of the bearing member (25) which is preferably also formed as a spherical surface.

6. A grab device according to any one of the claims 3 to 5, characterised in that the ring (22) is connected to the central web (21), preferably by a screwed connection or a non-positive andlor form-fit connection.

4

7. A grab device according to claim 2, characterised in that the cylinder holding member (24) is in the form of a ring support having an L-shaped cross section and is provided with a receiver for the bearing member (25) arranged between two legs of the ring support.

8. A grab device according to claim 2, characterised in that the bearing member (25) is substantially triangular in cross section, the triangular shape preferably being approximately rectangular and the catheti lying against the legs of the ring support and the hypotenuse, which is formed as a spherical surface, lying against the spherical surface (23) of the ring (22).

9. A grab device according to any one of the claims 3 to 8, characterised in that the ring (22) is screwed to a bearing cover (27) connecting and preferably clamping the cylinder holding member (24) to the central web (21).

10. A grab device according to claim 2, characterised in that between the bearing cover (27) and the ring (22) a push-on ring (26) is disposed which consists of an elastomer.

11. A grab device according to claim 2, characterised in that the push-on ring (23) allows for slewability of the cylinder(s) from 2 to 40, preferably 30.

12. A grab device according to claim 10, characterised in that the eiastomer has a hardness of less than 75 shore, preferably between 30 and 40 shore.

13. A grab device according to claim 1, characterised in that the carrying piece (7) consists of a holding device (8) arranged between two guide.members (9) guiding the legs (6) of the grab arms (2), said support device (8) having at least one central web (21) and being detachably connected to the guide members (9).

14. A grab device according to claim 13, characterised in that the holding device (8) is screwed to the guide members (9).

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15. A grab device according to claim 13, characterised in that the holding device (8) is formed as a cross arm having connecting sheet metal plates (10) on its ends to which the guide members (9) can be mounted.

16. A grab device according to claim 13, characterised in that the guide members (9) consist of a guiding part (11) and bilaterally arranged cast parts (12) which are respectively formed as tubular components having a substantially rectangular and preferably cuboid cross section.

17. A grab device according to claim 16, characterised in that the guiding part (11) is provided in the central portion thereof with a guide pin (13) extending parallel to the grab arms (2) and arranged between the legs (6) of two opposingly arranged grab arms (2).

18. A grab device according to claim 16, characterised in that at least one guiding web is respectively arranged in the cast parts (12).

19. A grab device according to claim 16, characterised in that the cast parts (12) are welded to the guiding parts (11).

20. A grab device according to claim 16, characterised in that bearings are embedded in the cast parts (12) for supporting and guiding the legs (6) of the grab arms (2).

21. A grab device according to any one of the claims 1 to 20, characterised in that at least one cylinder (16) of the piston-cyiinder unit (15) is provided in its bottom face with a manometer (32) indicating the carrying capacity of the grab arms (2).

22. A grab device constructed arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.