GB2370828A

GB2370828A - Gripper and method of unstacking elongate work pieces

Info

Publication number: GB2370828A
Application number: GB0127787A
Authority: GB
Inventors: Ludwig Schweiger
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-11-21
Filing date: 2001-11-20
Publication date: 2002-07-10
Anticipated expiration: 2021-11-20
Also published as: DE10057690A1; ITMI20012439A1; GB2370828B; GB0127787D0; FR2816930B1; DE10057690C2; FR2816930A1

Abstract

The invention discloses a simpler and more reliable method for automatically unstacking, separating and distributing stacked work pieces, in particular, squared timbers 7, by automatically lifting off and separating the work pieces by means of a gripping device 3 that simultaneously engages on the top surface and the front surface of the respectively first work piece, lifts the work piece off the stack and then transports and deposits or distributes the work piece. The invention also discloses a new unstacking and loading device (1) with a gripping device (3) that can be automatically displaced in the region of the stack (8) and a delivery station (9) and/or an additional processing device with the aid of a sensor-controlled double linear guide or double parallelogram guide (2) that is preferably driven hydraulically, wherein said gripping device contains at least one claw pair (4).

Description

METHOID AND DEVICE FOR AUTOMATICALLY UNSTACKING, SEPARATING

AND DISTRIBUTING WORK PIECES

The invention pertains to a method and a device for unstacking, separating and distributing work pieces, for example, long edged work pieces that preferably consist of wood, in particular, squared timbers. The invention specifically pertains to a method and a device for automatically removing stacked timber products from the respective stacks (i.e., unstacking), transporting the individual work pieces to a delivery station, preferably a processing or additional processing station, and cyclically delivering or distributing the separated work pieces.

The manual loading of machines, in particular, automatic timber processing machines, with timber products is laborious and time-consuming. This is the reason why various methods have been proposed for directly transporting work pieces, e g., squared timbers, from the stack to the feed unit of a processing machine in a timely fashion without requiring any manual manipulations. Tilting platforms are conventionally utilized for this purpose, wherein the top layer of work pieces slides over the top edge of the guide rail under the influence of the gravitational force once a certain lifting height is reached and then downward on a guideway that is inclined toward the processing station. The top layer of work pieces is stopped at the end of the guideway by means of a limit stop rail (see, for example, DE-OS 152 727).

Timbers with a round or polygonal cross section can be unstacked by means of gripping devices, the claw pairs of which are sufficiently large for encompassing the diameter of the respective timbers. However, squared timbers that are stacked in the form of packets cannot be encompassed or taken hold of on two opposing lateral surfaces with gripping devices of this type because the adjacent work .

- 2 - pieces tightly adjoin one another in the stack and the claws are usually unable to penetrate into the gaps between the squared timbers which may also have different widths.

The present invention is based on the objective of developing a new method that makes it possible to eliminate the disadvantages of the state of the art and to easily and reliably unstack work pieces, for example, long edged work pieces, in particular, squared timbers, without requiring additional set-up times, i.e., to individually remove the work pieces from the respective stacks. In this case, the separated work pieces are transported to a delivery station, preferably a processing or additional processing station, and then deposited or distributed, preferably in a cyclic fashion The invention also aims to develop a new device for carrying out this method.

These objectives are attained with the present invention.

The invention consequently pertains to a method for automatically unstacking, separating and distributing work pieces, for example, long edged work pieces, in particular, long edged timber products such as squared timbers, by lifting off and separating the first work piece from a stack ("packet"), transporting the work piece to a delivery station, depositing the work piece and repeating this cycle, wherein said method is characterized by the fact that the work piece is simultaneously taken hold of on the top surface and the front surface by means of a gripping device, lifted off the stack and then transported and deposited. The invention also pertains to an unstacking and loading device (1) for carrying out this method, wherein said device contains a gripping device (3) that can be

- 3 - automatically displaced in the region of the stack (8) and a depositing station (9) and/or an additional processing station with the aid of a sensor-controlled double linear guide (in the horizontal and vertical direction) or a double parallelogram guide (2) that preferably is driven or actuated hydraulically, and wherein the unstacking and loading device (1) is characterized by the fact that the gripping device (3) contains at least one claw pair (4).

The drive or drives of the device (1) may, for example, be realized hydraulically, pneumatically, mechanically and/or electrically The linear guide or parallelogram guide (2) is preferably driven hydraulically, with the gripping device (3) preferably being driven pneumatically.

The claw pair is designed in such a way that it is able to encompass from the top and the front surface the respectively first work piece - i.e., the work piece situated on the outside in the top layer of the stack -

e.g., a squared timber, and to take hold of the work piece when the claw pair is closed. While the claw pair is closed, the claws are slightly pressed into the respective timber surfaces. Each claw contains at least one clutch, prong or spike.

Both claws of the claw pair usually can be turned in the gripping direction. Under certain circumstances, it may suffice if only one of the two claws can be turned.

The invention is described in greater detail below with reference to Figures 1-5.

Figure 1 shows a schematic representation of the unstacking and loading device according to the invention [in the following referred to as the "device" (1)]. In this figure, the reference symbol (2) identifies the parallelogram guide with hydraulic cylinders, the reference symbol (3) .',

4 - identifies the gripping device with the claw pair (4), the reference symbol (5) identifies a support rail, the reference symbol (6) identifies a limit stop rail, the reference symbol (7) identifies a squared timber, the reference symbol (8) identifies a stack of squared timbers, the reference symbol (14) identifies an intermediate strip and the reference symbol (15) identifies the foundation.

Figure 2 shows in the form of arrows the typical moving cycle of the claw pair (4) of the device (1) according to the invention, namely in four positions (4a-4d). The stack (8) of squared timbers (7) which is delivered in the form of a packet rests on the support rails (5). The limit stop rails (6) are arranged perpendicular thereto. After the gripping device (3) is displaced from the starting position a into the position d via the positions b and c by means of the parallelogram guide, the claws (4) take hold of the first work piece from the top and the front and transport the work piece into the delivery position d on the path shown. In this position, the work piece is deposited on the delivery table or the magazine (9) which is held by the delivery station support (10). The cycle is then repeated until the unstacking process is entirely or partially completed. In the embodiment shown in Figure 3, the gripping device (3) of the device (1) according to the invention contains a claw pair (4) that is mechanically coupled - in this case, by means of gear rims. However, it would also be conceivable to provide a separate drive.

The centering angle (11) that is arranged on the gripping device in this embodiment is placed onto the top surface of the work piece to be taken hold of with its upper limb. Its other limb is pressed against the front surface of the work piece. In the open state, the tips of the gripping claws are situated outside of the centering angle.

..

- 5 - The gripping device (3) is moved over the surface of the stack by means of sensors and a corresponding control, namely toward the lateral surface of the work piece which does not adjoin an adjacent work piece and toward its top surface until both limbs of the centering angle (11) adjoin the work piece. The claw pair (4) is turned toward the work piece by means of a lever that is, for example, driven by a lifting cylinder (12). When the claw pair is closed, the tips of the claws are slightly pressed into and rigidly hold the work piece. The gripping device (3) with the work piece suspended thereon is then displaced toward the delivery station (the delivery table or delivery platform or the magazine) (9), and the work piece is deposited at this location by opening the claw pair (4). The described work cycle is repeated until the entire stack is processed.

The point at which the stack (8) is depleted can be detected by means of an additional sensor or a displacement transducer of the gripping device (3). Once this point is reached, a stand-by packet can be manually or mechanically transported to the limit stop rail (6).

Figure 4 shows a supplementary apparatus of the device (1) according to the invention. This supplementary apparatus may be required in instances in which work pieces that adhere to one another or become frozen together during the winter months interfere with the lifting and separating process, for example, because adjacent work pieces are carried along when the first work piece is raised. Sensors (not shown in Figure 4) that register the undesired lifting of adjacent work pieces are provided for such instances, with said sensors generating an error message and initiating corresponding countermeasures. These countermeasures include, for example, the opening of the gripping claws such that the work pieces are separated from one another by means of a free fall, as well as shaking off ..... .....

6 - or pressing off the adhering work piece, for example, by means of a pressing cylinder (13).

Figure 5 shows, among other things, that intermediate strips (14) are frequently inserted between the respective layers of the stack so as to securely transport the stacked packets (8) or dry the work pieces. When the first work piece of the new layer is raised, the intermediate strips (14) of the previously cleared layer are also raised on one side. The front ends of the intermediate strips (14) consequently are raised by the work piece while their rear ends remain on the last work piece of the layer (see Figure 5). During the course of the work piece transport, the end of the intermediate strips (14) travels along an arc-shaped path in this case. In order to prevent that the intermediate strips (14) prematurely fall back onto the stack, the gripping device is moved along a corresponding arc, an arc that is smaller than the arc traveled by the intermediate strip or even transversely.

It is also possible to initially raise the work piece such that it is moved away from the adjacent work piece in a slightly inclined fashion, i. e., the work piece is removed from the layer situated underneath and then horizontally displaced. During this process, the intermediate strip (14) is pushed over the work piece to be transported.

During the ensuing vertical movement that may also take place simultaneous with the horizontal movement, the intermediate strip (14) slides into the space provided between the stack (8) and the delivery station support (10) due to its inclined position and can be automatically transported away, for example, with the aid of a conveyor belt. In another variation for removing the intermediate strip (14), the last work piece of the respective layer is ... ..

- 7 raised, moved over the stack away from the limit stop rail (6), lowered until it is situated slightly above the top surface of the stack and then moved in the direction of the limit stop rail (6) such that the intermediate strips (14) which lie on the top surface of the stack are pushed away by the work piece. The gripping device (3) then moves upward to the delivery table (9) over the limit stop rail (6). In the search mode, a possibly existing obstacle can be detected and bypassed with the aid of correspondingly designed sensors.

The position of the last work piece removed from the stack can be registered with the aid of an intelligent control.

During the next work cycle, the claw pair (4) is returned to this position or displaced by a corresponding distance minus the width of one work piece. A predetermined distance from the top surface of the stack is preferably observed when the gripping device is horizontally displaced.

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Claims

g CLAIMS

. 1. A method for automatically unstacking, separating and distributing work pieces, in particular, long edged timber products, by lifting off and separating the first work piece from a stack ("packet"), transporting said work piece to a delivery station, depositing the work piece and repeating this cycle, characterized by the fact that the work piece is simultaneously taken hold of on the top surface and the front surface, lifted off the stack and then transported and deposited by means of a gripping device.
2. A method according to claim 1, characterized by the fact that the work pieces are long and edged.
3. A method according to claim 2, characterized by the fact that the work pieces consist of squared timbers.
4. A method according to one of claims 1-3, characterized by the fact that deviations in the position of the stack from the horizontal line andior the vertical line and an inclined position of the work pieces are compensated by automatically adapting the gripping device horizontally and vertically and then automatically aligning the gripping device.
5. A method according to one of claims 1-4, characterized by the fact that the top edge of a stack and the top edge of one side of the work piece are initially determined in a search mode that is controlled by sensors
6. A method according to one of claims 1-5, characterized by the fact that the work pieces are deposited at different locations.

.. . ...

_q _
7. A unstacking and loading device for carrying out the method according to one of claims 1-6, with a gripping device (3) that can be automatically displaced in the region of the stack and a delivery station (9) and/or an additional processing device with the aid of a sensorcontrolled double linear guide or double parallelogram guide (2), characterized by the fact that the gripping device (3) contains at least one claw pair (4).
8. A device according to claim 7, characterized by the fact that the gripping device is provided with a centering angle (11) in order to optimally position the gripping device, wherein the limbs of the centering angle adjoin the front surface and the top surface of the work piece when the gripping device (3) engages thereon.
9. A device according to claim 8, characterized by the fact that the limbs of the centering angle (11) exert pressure upon the work piece.
10. A device according to one of claims 7-9, characterized by the fact that the gripping device (3) presses the entire layer of the stack against a limit stop rail (6) when it engages on the work piece.
11. A device according to one of claims 7-10, characterized by the fact that the claw pair (4) is mechanically coupled such that it carries out a synchronous arc-shaped movement in opposite directions in order to penetrate into the work piece with the claw tips;
12. A device according to one of claims 7-11, characterized by the fact that the claw pair (4) carries out a linear movement.

i.. ...

Jo -
13. A device according to one of claims 7-12, characterized by the fact that the claws are mechanically, hydraulically or pneumatically geared such that they contact the work piece simultaneously or at different times.
14. device according to one of claims 7-13, characterized by the fact that the individual claws are mechanically, hydraulically or pneumatically geared such that they act upon the work piece with different pressures.
15. A device according to one of claims 7-14, characterized by the fact that both claws are movable.
16. A device according to one of claims 7-14, characterized by the fact that only one of the two claws is movable, wherein the stationary claw is moved downward or laterally such that its tip penetrates into the work piece, and wherein the movable claw is subsequently closed.

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