CA2342676A1

CA2342676A1 - Depalletizing tool for an industrial robot and method for operating the same

Info

Publication number: CA2342676A1
Application number: CA 2342676
Authority: CA
Inventors: Paul Leblanc; Sylvain-Paul Morency; Dominic Prevost; Sylvain Boily
Original assignee: Axium Automation Inc
Current assignee: Axium Automation Inc
Priority date: 2001-03-30
Filing date: 2001-03-30
Publication date: 2002-09-30

Description

OPERATING THE SAME
Field of the invention The present invention relates to a depalletizinc~ tool for an industrial robot.
The tool is provided with a prehension mechanism and sensors required to allow the prehension of piles of a certain height and formed of identical articles stacked with a certain stability, without any fasteners, over several layers separated by separators exceeding on a side. Furthermore, the present invention also relates to a method for operating the above-mentioned depalletizing tool.
Description of the prior art 1~ Several manufacturing industries need to pack their product into boxes.
These boxes are often shipped by the manufacturers., in an unfolded and stacked manner, on pallets. The piles of boxes need to be handled manually in order to transfer them from the pallet to a machine whose function is to form the boxes and to insert the product therein. The main problems to which are confronted these industries are the costs related to the use of manual labor and the industrial illnesses related to the repetitive handling of moderately heavy loads.
Confronted to this type of problem, industrialists are turning themselves more and more towards automated solutions allowing to replace human beings by an automated system.
An automated solution is generally defined as a set of mechanisms governed by a control system accomplishing a specific functionality. There exist on the market specialized systems capable of accomplishing depalletization work but only under very specific constraints. These constraints are such that the industries must consider robotized solutions which are much less constraining.

2 A robotized solution is defined as a system using an industrial robot with four degrees of freedom or more as well as a tool specifically designed to be affixed on the robot and accomplish a very well defined task. There exist on the market robotized solutions capable of accomplishing depalletization work but the latter also have certain constraints. These constraints are:
~ the pallets must always be placed at the same location;
~ the set of articles on the pallet must always; be at the same location on the pallet;
~ the articles must be of the same dimension;
~ the piles of articles must be fastened individually or the article must be a formed box;
~ the tool of the robot or the downstream machine must remove the fasteners of the piles and dispose adequately of the fasteners {e.g.
straps).
One can find on the market vision systems allowing the digitalization of objects in three dimensions. It is possible to adapt such a system to an industrial robot tool and to produce a computer program capable of processing the digital images and allowing a tridimensional tracing. Unfortunately, the costs involved would be prohibitive for an industrial application intended for a very competitive market.
Prehension is a very complex function even for human beings and there is no industrial robot tool presently on the market which is capable of carrying out such a complex task to accomplish while remaining independent of the physical dimensions of the articles.

3 Summary of the invention The main object of the present invention is to provide a depalletizing tool for an industrial robot and method for operating the same which satisfy some of the above-mentioned needs and which are thus an improvement over what is known in the prior art.
More particularly, a first object of the invention is to provide a depalletizing tool for an industrial robot capable of carrying out the prehension of piles of a certain height and formed of identical articlea stacked on a pallet with a certain stability, without any fasteners, over several layers separated by separators exceeding on a side.
A second object of the invention is to providE: a method for operating the above-mentioned depalletizing tool, said method being capable of carrying out a tridimensional tracing in order to locate the pallet in a. (X, Y, Z) coordinate system referenced to the robot.
In accordance with a preferred embodiment: of the invention, the above objects are achieved by a depalletizing tool to be used with an industrial robot, the tool being devised for carrying out the prehension of piles of a certain height and formed of identical articles stacked on a pallet with a certain stability, without any fasteners, over several layers separated by separators exceeding on a side.
The tool is preferably equipped with two distance scanners, a proximity sensor, a prehension mechanism having a flexible spatula, a rigid spatula, a clamping plate, actuated by pneumatic cylinders and cooperating thereinbetween to accomplish the above-mentioned task.
Also according to another aspect of the present invention, there is provided a method for operating the above-mentioned industrial robot tool. The method comprises the steps for allowing the tool to locate a corner of the pallet with a scanner and position itself with the other scanner close to the upper

4 separator, on the exceeding side. The tool then moves closer to deform the extremity of the flexible spatula upon contact of the separator actuating the proximity sensor. The prehension is carried out by inserting the flexible spatula under the pile, by inserting the rigid spatula under i:he flexible spatula and by clamping thereover with the clamping plate.
The invention and its advantages will be better understood by reading the following non-restrictive description of preferred embodiments thereof, made with reference to the accompanying drawings.
Brief description of the drawincts Figure 1 is a perspective view of a pile of articles stacked on a pallet according to a preferred embodiment of the invention, a depalletizing tool being shown schematically positioned with respect to said pile.
Figure 2 is a perspective view of a portion, according to a preferred embodiment of the invention, of the tool shown in Figure 1.
Figure 3 is a side elevational plan view illustrating a step of the method for operating the depalletizing tool shown in Figure 2 with respect to the pile shown in Figure 1.
Figure 4 is a side elevational plan view illustrating another step of the method for operating the depalletizing tool shown in Figure 2 with respect to the pile shown in Figure 1.
Figure 5 is a side eievational plan view illustrating yet another step of the method for operating the depalletizing tool shown in Figure 2 with respect to the pile shown in Figure 1.

Figure 6 is a side elevational plan view illustrating yet another step of the method for operating the depalletizing tool shown in F=igure 2 with respect to the pile shown in Figure 1.

5 Figure 7 is a perspective view of the depalleti:zing tool shown in Figure 2, said tool being shown in its entirety Description of the preferred embodiments In the following description, the same numerical references refer to similar elements. The embodiments shown in the figures are preferred.
Moreover, although the present invention was primarily designed for use with an industrial robot for depalletizing purposes, it could be used with other types of objects of different fields for other purposes, e.g. sorting applications, etc., as apparent to a person skilled in the art. For this reason, expressions such as "depalletizing" andlor "arnciesw ana any Vll lt~l 1 GICI GI ~lr~..~ umm v«
~..~
expressions equivalent thereto should not be taken as to limit the scope of the present invention and include all other objects with which the present invention could be used and may be useful.
In addition, although the preferred embodirnent of the present invention as shown comprises components such as distance scanners, sensors (optical, laser, proximity), a flexible spatula, a rigid spatula, a clamping plate, a support plate, pneumatic cylinders, etc., not all of these components are essential to the invention and thus should not be taken in their restrictive sense, i.e. should not be taken as to Limit the scope of the present invention. It is to be understood, as also apparent to a person skilled in the art, that other suitable components and cooperations thereinbetween may be used for the depalletizing tool according to the present invention, as will be explained hereinafter, without departing from the scope of the invention.

6 Moreover, expressions such as "robot" and "tool'', as well as any equivalent expressions andlor compound words thereof, may be used interchangeably in the context of the present description. The same applies for any other mutually equivalent expressions, as also apparent to a person skilled in the art.
Furthermore, it is to be understood that the e;Kpression "articles" as used in the context of the present description refers to various different objects which may be used with the present invention, whether these objects are of substantially 2-D and 3-D form, SUCK as metal sheets, cardboards, unfolded boxes, formed boxes, plastic containers, etc., as apparent to a person skilled in the art.
The depalletizing tool according to the preferred embodiment of the invention as shown in the accompanying drawings is an industrial robot tool provided with sensors arranged so as to carry out a tridimensional tracing in space, and provided also with a prehension mechanism capable of handling articles 1 laid out on a pallet 2, as shown in figure 1, and separated into layers by means of separators 3 used mostly to add stability to the set of articles on the pallet.
According to the present invention, the sensors of the tool are positioned such that the robot can, firstly, trace the pallet approximately in its (X, Y, Z) reference system. Afterwards, by means of a height calculation based on the height of the piles of articles and of a search movement, the robot locates the separators precisely and proceeds to the prehension.
The prehension mechanism of the tool preferably consists of a layout of spatulas capable of inserting themselves under the pile in a sequence and in a very precise robot movement and also of a clamping plate resting more or less firmly on the flop of the pile while and after the inse~~tion of the spatulas in order to complete the prehension. Following a prehension, the robot may then transport

7 the pile of articles towards a very precise location such as a feeding container of a production machine.
More particularly, the industrial robot tool, according to a preferred embodiment of the invention, is provided, as shown in figure 2, with an optical sensor 5, a laser sensor fi, an inductive proximity sensor 7, a flexible spatula 8 actuated by a pneumatic cylinder (not shown in the figures), a rigid spatula 9 actuated by a pneumatic cylinder (not shown in the figures), and a support plate 4 for the various components 5, 6, 7, 8 and 9 of the tooll. Preferably also, the tool is further equipped, as shown in figure 7, with a clamp>ing plate 10 actuated by a pneumatic cylinder (not shown in the figures) and with suction cups 11.
The preferred working principle of the tool is described as follows. By means of the optical sensor 5, the robot carries out a vertical tracing over the left corner of the pallet (see figure 1). This tracing routinE: allows the robot to read the height along the Z direction over the pile 1 and to deduce the positions X and Y
by means of its internal references. The approximate dimensions of the pile 1 of articles on the separator 2 being known parameters, the robot calculates the position of the separator 2 and positions its tool approximately as shown in figure 3 so that the edge of the flexible spatula 8 is close to the separator 2. Then, by means of the laser sensor 6, the robot validates the horizontal position of the pile 1 and approaches the flexible spatula 8 of the tool towards the pile 1, while always remaining away from the separator 2.
Once the robot tool is thus positioned, the robot begins a precise search routine for the separator 2. This routine consists in making, as shown in figure 3, a small movement horizontally towards the pile 1 fiollowed by a small movement vertically from top to bottom. After this last movement, the robot verifies if the proximity sensor 7 is activated by the deformation of the edge of the flexible spatula 8 touching the separator 2, as shown in figure 4. If the proximity sensor 7 is not activated, the robot brings up the tool to the initiating height and.
repeats the search routine until the proximity sensor 7 is activa~'~ed.

8 After the precise localization of the separator 2, the robot brings forward the flexible spatula 8 of the tool by means of a pneumatic cylinder in order to insert it under the pile 1 between the last article of lrhe pile 1 and the separator 2, as shown in figure 5. The robot then actuates the rigid spatula 9 of the tool by means of a pneumatic cylinder in order to insert it under the flexible spatula 8, as shown in figure 6. At the same time that the rigid spatula 9 is inserted, the robot actuates the clamping plate 10 shown in figure 7 by means of a pneumatic cylinder in order to apply a certain pressure on the top of the pile in order to maintain the articles in place and prevent unwanted displacements. The robot has completed the prehension cycle with its tool. It can then displace the pile 1 and lay it down at a precise location.
The prehension cycle is repeated until the robot has removed all the piles 1 lying on the separator 2. When there is no more piles on the separator 2, the robot removes the separator 2 by means of the suction cups 11 of the tool. In order to do so, the robot positions the tool over the separator 2 and lowers the tool so that the suction cups 11 touch the separator 2. Using suction, the suction cups raise the separator 2. The robot can then displace the separator 2 and lay it down at a precise location. These steps are repE~ated until there is no more piles 1 on the pallet 3.
According to another particular embodiment of the invention, the position of the flexible spatula 8 in the pile 1 is knovvn by the robot by means of a positioning sensor fixed to the pneumatic cylinder of the flexible spatula 8.
The robot can determine the penetration distance of the flexible spatula 8 in the pile 1 during the insertion and determine if the insE;rtion is successful or not. If the insertion is not successful, the robot removes the flexible spatula 8 from the pile 1, raises or lowers the tool with a certain increment and restarts the insertion of the flexible spatula 8. This particular embodiment allows, among other things, to not use separators 2 between the layers of thE; piles 1, provided that the articles forming the pile are of a minimal thickness.

9 Of course, numerous modifications could be made to the above-described embodiments without departing from the scope of the invention as apparent to a person skilled in the art.