NL2005966C2

NL2005966C2 - A gripper assembly and a handling system.

Info

Publication number: NL2005966C2
Application number: NL2005966A
Authority: NL
Inventors: Ronald Walter Neutel; Cornelis Franciscus Maria Bootsman; Johannes Adrianus Maria Schaik
Original assignee: Roboxis B V
Priority date: 2011-01-07
Filing date: 2011-01-07
Publication date: 2012-07-10

Description

P30517NL00/MVE

A gripper assembly and a handling system

The invention relates to a gripper assembly comprising a frame and at least two gripper fingers forming a gripper unit, wherein each gripper finger has a gripper finger body that is mounted to said frame, and wherein each gripper finger body is provided with at least one inflatable bladder that is effective in a space in between the at least two gripper finger 5 bodies, said bladder being adapted to grip an object.

Such a gripper assembly is disclosed in GB 2.357.274. In this publication, the frame is formed by a plate. Each gripper finger comprises a gripper finger body provided with a bladder made of an elastic material which is sealed around the edges to form the gripper 10 finger. By supplying a medium to the bladder, the bladder can be inflated, thereby decreasing the effective distance between the gripper fingers. To increase the distance, the bladders can be deflated. Thus by inflating and deflating the bladders, an object between the gripper fingers can be gripped or released respectively.

15 A disadvantage of this known gripper assembly is that when variable-shaped objects, such as sweet peppers, have to be gripped, the average time to grip an object may not be satisfactory as due to the different shapes of the objects it may take more time for smaller objects to be gripped by the fingers upon application of a suitable gripping force by the bladders.

20

It is therefore an object of the invention to provide a gripper assembly which allows a fast gripping operation, and preferably also a fast release operation.

This object is achieved by a gripper assembly according to the preamble of claim 1, 25 characterized in that at least one, preferably all, gripper finger bodies are moveably, preferably translationally, mounted to the frame, and in that the gripper assembly comprises actuation means to move the gripper finger bodies of the at least two gripper fingers relative to each other to adapt the size of the space in between the at least two gripper finger bodies in addition to inflation of the bladder.

An advantage of the gripper assembly according to the invention is that the distance between the gripper fingers can be adapted faster to the size of the object. In the mentioned 30 -2- prior art, the distance between the gripper finger bodies is determined by the largest object that needs to be handled. For smaller objects, the distance between the gripper finger bodies is relatively large and it thus takes more time to inflate the bladders and grip the object than for a larger object. By being able according to the invention to adapt the distance 5 between the gripper finger bodies, the distance between the gripper finger bodies and the object can be reduced for smaller objects, so that it takes less time for the bladders to inflate and grip the object, thereby increasing the speed of the gripping operation.

Another advantage is that the same can be applied for the release operation of the gripper 10 assembly. In addition to deflation of the bladder, a gripper finger can be retracted as well to quickly release the gripper finger from the object.

The moveability of the gripper fingers also allows to inflate the bladders prior to gripping in which gripping is subsequently performed by moving the gripping fingers towards each other. 15 The combination, in which moving and inflating happens at least partially simultaneously, is also possible.

In a suitable embodiment, another advantage is that the contact area between a small object and the bladders can be relatively large as the gripper finger body can be positioned closer 20 to the object than in the prior art, so that the gripping force is distributed over a larger area and thus a more delicate grip can be obtained in which the maximum pressure exerted on the object can be below a predetermined value to minimize damage of the object, which is especially important in case of horticultural objects, e.g. sweet peppers, tomatoes and fruit.

25 In an embodiment, the actuation means are configured to keep the centre of the space in between the at least two gripper finger bodies stationary relative to the frame in at least one horizontal direction. The advantage of this configuration is that positioning the gripper fingers around an object in said at least one horizontal direction only requires appropriate positioning of the frame and thereby the centre of the space - provided that the space in 30 between the at least two gripper fingers is large enough to receive the object - and not requires positioning of the frame in dependency of the actual position of the centre of the space thereby simplifying the control of the gripper assembly.

In an embodiment, the gripper assembly has a single pair of gripper fingers provided 35 opposite each other to receive the object in between the pair of gripper fingers. Usually, the use of two gripper fingers is sufficient to controllably grip an object, especially as the -3- inflatable bladder in inflated state may more or less encompass portions of the object which provides a stable gripping operation.

In an embodiment, the gripper assembly comprises a frame supporting multiple pairs of 5 gripper fingers, each pair associated with a distinct space for receiving an object to be gripped, wherein each pair forms a gripper finger pair unit and is configured to receive an object in between the respective pair of gripper fingers, and wherein the actuation means are configured to move the gripper finger bodies of a pair of gripper fingers towards or away from each other in a gripping direction independently of one or more other pairs of gripper 10 fingers. As a result, multiple objects can be gripped, e.g. simultaneously, with the gripper assembly and each pair of gripper fingers is able to adjust its distance between the gripper fingers to the size of the respective object. Simultaneously performing the gripping actions further increases the speed of the gripping operation, especially when the multiple objects need to be handled, e.g. packaged, together.

15

In an embodiment, the gripping finger pair units are mounted on the frame so as to be moveable - as a unit - relative to other gripping finger pair units, for instance each unit is moveable perpendicular to the gripping direction or rotatable about the centre of the space in between the gripper fingers of a pair of gripper fingers. As a result the objects gripped by 20 respective gripping finger pair units can also be positioned or orientated relative to each other, which may be advantageous for packaging reasons.

In an embodiment, each gripper finger extends in vertical direction having a height and width much larger than a thickness of the gripper finger. The gripper finger thus has a thin wide 25 configuration which enables the gripper finger to easily get between an object and another structure, e.g. a side wall of a conveyor carrying the object or the sidewall of a packaging box. The thickness of the gripper finger with a non-inflated bladder may for instance be at most 10mm, preferably at most 5mm, wherein the length and width may in the order of a few centimetres, e.g. 5-10cm.

30

In an embodiment, the width of each gripper finger is at most the average length of a sweet pepper, so that positioning the sweet peppers end to end and close to each other while being gripped by the gripper fingers is possible without interference between gripper fingers of adjacent gripper finger pair units. It is envisaged that other widths and sizes of the gripper 35 fingers may also be suitable.

-4-

In an embodiment, each gripper finger body is formed by a box, e.g. a rectangular box, having an opening on one side that is covered by a membrane to define the inflatable bladder, the other sides of the box being rigid, the box having an opening to be connected to a medium supply, i.e. a source of medium, e.g. a gas or a fluid, to inflate the bladder. The 5 source of medium, i.e. a medium supply, may also be configured to deflate the bladder, but this may also be done by a connection of the box to a low-pressure environment, e.g. ambient pressure, vacuum, or an environment with a pressure in between thereof.

In an embodiment, each gripper finger body is formed by a plate, e.g. a planar plate, covered 10 by a membrane that is sealed around the edges thereof to define the inflatable bladder, and wherein a medium supply is present to introduce said medium in between the plate and the membrane to inflate the bladder.

The above described membranes may comprise elastic, e.g. elastomeric, material. An 15 advantage is that due to the elastic properties of the membrane, the membrane will actively retract from the object when the bladder is deflated and even aid in deflating the bladder. Preferably, the membrane is thin to minimize the stresses in the material and improve the deformability of the membrane as inflating the bladder and encompassing portions of the object can then be done using a relatively low pressure in the bladder.

20

In an embodiment, the gripper assembly comprises a medium supply having a cylinder and a piston moveable within said cylinder such that there are two separate chambers inside said cylinder separated by the piston, and wherein the at least one bladder of the gripper fingers are in communication with one of said chambers of the cylinder, said chamber being filled 25 with medium so that movement of said piston inside the cylinder is able to inflate and deflate the bladder.

The advantage of the medium supply as described above is that the cylinder provides a predetermined amount of medium to inflate the bladder, wherein the volume of medium can 30 be supplied to the bladder in a controlled, reproducible and quick manner.

In an embodiment, the gripper assembly comprises a medium supply having a chamber which is connected to a high pressure medium source and to the at least one bladder of the gripper fingers, wherein a valve is provided between the chamber and the high pressure 35 medium source and between the chamber and the at least one bladder, and wherein the at least one bladder is also connected to a low pressure environment, e.g. a vacuum source, via a valve.

-5-

Such a medium supply allows to inflate and deflate the bladder by performing the following steps for inflating: a) closing the valve between the bladder and the chamber; 5 b) opening the valve between the chamber and the high pressure source to allow medium to enter the chamber at high pressure; c) closing the valve between the chamber and the high pressure source to trap medium inside the chamber; d) opening the valve between the bladder and the chamber to allow medium to flow to 10 the bladder and thereby inflate the bladder, and by performing the following steps for deflating: e) closing the valve between the bladder and the chamber; f) opening the valve between the bladder and the low pressure environment to deflate the bladder.

15

As a result, inflating and deflating the bladder can be done quickly in a reproducible and controlled way.

It is possible that each bladder of a gripper finger is connected to a separate medium supply 20 as described above as this allows separate control of the inflation of each bladder, but -especially when such separate control is not necessary - two or more bladders may also be connected to the same medium supply. When two or more bladders are connected to the same medium supply, then separate control may even be possible, for instance when there are separate valves provided between a high-pressure source and each bladder.

25

In an embodiment, the gripper assembly comprises a frame which supports three gripper finger pair units, each unit having two gripper fingers arranged opposite each other to grip a sweet pepper. The gripper finger pair units are positioned in a line next to each other. The gripper fingers are moveable towards or away from each other, and the units are moveable 30 in a direction parallel to said line. Preferably, the units are each rotatable about a vertical axis. This embodiment is particularly suitable for gripping three sweet peppers at the same time, position and/or orientate them correctly for packaging, and subsequently transfer them to a packaging station or other conveyor whereafter the three sweet peppers can be packaged together.

The invention also relates to handling system to handle variable-shaped objects, comprising: - a conveyor for conveying objects in a conveying direction; 35 -6- - a gripping device having a motion device with a gripper assembly according to the invention to displace the objects from the conveyor to another location, e.g. another conveyor or a packaging location; - a sensor system to measure the position and one or more dimensions of the conveyed 5 objects prior to being engaged by the gripper assembly; and - a control system to control the gripping device based on input of the sensor system.

The sensor system is able to provide information which can be used by the control system to control the gripping device. Preferably, the control system is adapted to control operation of 10 the actuation means in order to move the moveable gripper finger bodies based on position and dimensional information of the sensor system. The sensor system can be for instance an optical system, i.e. a visual system using one or more cameras.

In an embodiment, the sensor system is able to measure the orientation of the objects, and 15 the control system is able to control the position of the gripper fingers of the gripper assembly based on said orientation, which may be advantageous when the object comprises protrusions or part, e.g. the stalk of a sweet pepper, which may not contact the bladders to prevent damage to the bladders. The gripper units of the gripper assembly may therefore be rotatable about a vertical axis to position the gripper fingers of a respective unit properly 20 relative to the object.

In an embodiment, the gripper assembly comprises multiple gripper units with corresponding gripper fingers, and the control system is configured to simultaneously grip multiple objects without changing the orientation and position of the objects and subsequently after gripping 25 changing the relative positions between the multiple objects e.g. for packaging reasons. As a result, the objects can be gripped without damaging the objects and without losing information about the position of the objects, so that the position subsequently can be altered in an open loop manner, i.e. without requiring additional measurements on the position.

30

The invention also relates to a method for gripping a variable-shaped object from a conveyor with a gripper assembly according to the invention, comprising the following steps: a) measuring the position and one or more dimensions of the object on the conveyor; b) positioning the gripper fingers at a predetermined distance from the contour of the 35 object; -Ίο) inflating the bladders of the gripper fingers such that the bladders contact the object simultaneously without moving the object, thereby gripping the object between the gripper fingers.

5 In an embodiment - during step c) - the bladder of the gripper finger that is farthest from the object to be gripped is inflated first, and corresponding to the difference in distance, the bladder of the gripper finger which is at a smaller distance is inflated with an appropriate time-delay to inflate the bladders of the gripping fingers such that the bladders contact the object simultaneously without moving the object. As a result of not moving the objects, no 10 position information is lost during gripping.

In an embodiment, the bladders are inflated to an equal extent, so that after gripping the object is automatically centred between the gripper finger bodies.

15 In an embodiment, the gripper assembly comprises a frame which supports three gripper finger pair units, each unit having two gripper fingers arranged opposite each other to grip a sweet pepper. The gripper finger pair units are positioned in a line next to each other. The gripper fingers are moveable towards or away from each other, and the units are moveable in a direction parallel to said line. The method than preferably comprises the following steps: 20 a) measuring the position and one or more dimensions of three sweet peppers on the conveyor; b) positioning the gripper fingers of each gripper finger pair unit at a predetermined distance from the contour of the respective sweet pepper; c) inflating the bladders of the gripper fingers such that the bladders contact the 25 respective sweet pepper simultaneously without disturbing the sweet pepper, thereby gripping the sweet pepper between the gripper fingers.

In an embodiment, the gripper finger pair units are rotatable about a vertical axis, so that the method further comprises the steps of: 30 - measuring the orientation of the sweet peppers thereby at least determining the position of the stalk of each sweet pepper; positioning the gripper fingers of each gripper finger pair unit at a predetermined orientation relative to the respective sweet pepper so that the stalk of the sweet pepper will not be contacted by the respective bladders 35 during gripping.

-8-

The invention will now be described in a non-limiting way by reference to the accompanying drawings in which like parts are referred to by like reference numerals and in which:

Fig. 1 depicts schematically a gripper assembly according to an embodiment of the invention in deflated state; 5 Fig. 2 depicts the gripper assembly of Fig. 1 in inflated state;

Fig. 3 depicts schematically a part of a gripper assembly according to another embodiment of the invention;

Fig. 4 depicts schematically a gripper assembly according to yet another embodiment of the invention; 10 Fig. 5 depicts a gripper finger of a gripper assembly according to a further embodiment of the invention in respectively side view of the gripper finger in deflated state, inflated state and in front view;

Fig. 6 depicts a gripper finger of a gripper assembly according to another embodiment of the invention in respectively side view of the gripper finger in deflated state, inflated 15 state and in front view;

Fig. 7 depicts a conveyor and a part of a gripper assembly according to yet another embodiment of the invention;

Fig. 8 depicts three objects in an exemplarily situation of how they can be positioned on a conveyor; 20 Fig. 9-11 depict a method to grip and position the three objects of Fig. 8;

Fig. 12depicts a gripper assembly according to a further embodiment of the invention;

Fig. 13 schematically depicts a handling system according to an embodiment of the invention;

Fig. 14 depicts a gripper finger for a gripper assembly according to another embodiment of 25 the invention.

Fig. 1 and 2 depict a gripper assembly GA according to an embodiment of the invention in respectively deflated and inflated state. The gripper assembly GA is shown in top view and comprises a frame FR to which gripper fingers GF1, GF2 are moveably mounted.

30

Each gripper finger GF1, GF2 comprises a plate PL as gripping finger body covered by a membrane ME which is sealed at the edges to form a bladder BL. In the deflated state, the thickness TH of the gripper fingers is small compared to the width Wl (see Fig. 2) and the length (not shown) of the gripper fingers.

A cylinder CY per gripper finger is provided. Alternatively, a cylinder per two or more gripper fingers could be provided to save parts and create a more simple gripper assembly. Here, 35 -9- each cylinder CY comprises a piston PI dividing the interior of the cylinder into two chambers CH1 ,CH2 such that the volume of each chamber is determined by the position of the piston PI. The piston PI is moveable via respective rods RO.

5 One of the chambers CH1 of the cylinder CY are in fluid communication with the respective bladders BL via a hole/opening in the plate PL and a conduit CO extending from the chambers CH1 to the respective hole. The chambers CH1 and respective conduits CO are filled with a medium, e.g. air or a suitable fluid.

10 In Fig. 1, the pistons PI are positioned in a retracted position in which most of the medium is in chamber CH1 such that the membrane ME is lying against the plate PL in a rest position and as a result, the gripper fingers occupy minimal space and the effective distance between the gripper fingers is maximal. An object OB can be received in between the two gripper fingers GF1, GF2 as shown in Fig. 1.

15

By moving the respective pistons PI such that the volume of chambers CH1 is decreased, medium is pushed through the conduits CO into the bladders BL thereby inflating the bladders BL until the object is gripped. This inflated state is depicted in Fig. 2. An advantage of the bladders is that the bladder is able to adapt its shape to the outer contour of the object 20 so that irregular objects such as sweet peppers can be gripped effectively without damaging the object as the pressure exerted on the object stays below a predetermined value due to spreading of the gripping force over the relatively large contact area.

The gripper fingers GF1, GF2 are guided by frame FR to allow movement in a gripping 25 direction GD. Between each plate PL and the frame a respective actuation member is provided to move and position the plate PL in the gripping direction GD and thus are able to move the plates towards and away from each other in the gripping direction. In Fig. 2, the frame and the actuation members are omitted for simplicity reasons.

30 Fig. 3 depicts schematically a part of a gripper assembly according to another embodiment of the invention. The assembly comprises multiple gripper fingers of which only one GF1 is shown. The construction of the gripper finger GF1 is similar to those of Fig. 1 and 2 and comprises a plate PL as gripper finger body covered by a membrane ME to form a bladder BL.

The bladder BL is connected to a chamber CH1 via a valve V1 and to a low pressure environment LPE, preferably vacuum, via a valve V2. The chamber CH1 is connected to a 35 - 10- high-pressure source HPS, e.g. compressed air, via a valve V3. This allows for the following inflation procedure: - the assumed starting point is that all valves V1 ,V2,V3 are closed; subsequently valve V3 is opened to allow medium from the high-pressure 5 source HPS into the chamber CH1; - when an equilibrium is reached, valve 3 is closed; inflation of the bladder can now be initiated by opening valve V1 to allow medium to flow from the chamber CH1 into the bladder BL; - when an equilibrium is reached, valve V1 is closed and valve V3 can be 10 opened again to fill the chamber CH1 again with medium for a next inflation.

Deflation of the bladder BL is done by opening valve V2, so that medium flows out of the bladder to the low-pressure environment until the membrane ME lies against the plate PL again.

15

The above inflation and deflation procedures can be performed at any time to grip or release an object.

In the abovementioned embodiments of Figs. 1-3, the degree of inflation can be regulated.

20 In Fig. 1 and 2 this can for instance be done by regulating the piston PI or by adapting the pressure inside chamber CH1. In Fig. 3 this can for instance be done by adjusting the time a valve is opened or closed or by adjusting the pressure inside the chamber CH1.

Fig. 4 depicts schematically a gripper assembly GA according to yet another embodiment of 25 the invention in side view. The gripper assembly comprises a frame FR to which two moveable gripper finger GF1 ,GF2 are mounted that are positioned opposite each other to receive an object OB in a space SP in between the two gripper fingers. The gripper fingers each comprise an inflatable bladder BL facing towards the space SP to grip the object OB as shown in Fig. 4. The bladder BL is thus in an inflated state in Fig. 4.

30

The moveability of the gripper fingers is indicated by the arrows AR. As can be clearly seen in Fig. 4, the gripper fingers GF1 ,GF2 are moveable relative to the frame FR towards and away from each other in a gripping direction parallel to arrows AR. To move the gripper fingers, actuation means are provided on the frame FR.

The actuation means comprise an endless belt EB having an upper part UP and a lower part LP, wherein said endless belt is running over pulleys PU1 and PU2 arranged on either side 35 - 11 - of frame FR. The endless belt EB is driven by a motor MO which drives pulley PU2 via belt BE.

In Fig. 4, the left gripper finger GF1 is connected to the upper part UP of the endless belt EB 5 via attachment member AB1, and the right gripper finger GF2 is connected to the lower part LP of the endless belt EB via attachment member AB2. By movement of the endless belt, one attachment member including the respective gripper finger will move in a corresponding direction and the other attachment member including gripper finger will move the same amount in the opposite direction, so that the centre CE of the space SP in between the two 10 gripper fingers remains stationary with respect to the frame FR. This allows for easy control, as driving the motor MO will determine the size of the space SP and positioning the frame FR determines the position of the centre CE of the space SP.

The attachment members AB1.AB2 are guided during movement along respective guiding 15 members GE1,GE2.

Fig. 5 depicts a gripper finger GF1 comprising a plate PL and a bladder BL forming membrane ME which is sealed around its edges except at the top side where it is connected to a tube or conduit TU to inflate or deflate the bladder BL. On the left hand side of the 20 figure, the bladder BL is filled with medium so that the bladder is shown in inflated state. In the middle, the bladder BL is connected to vacuum so that the membrane is lying against the plate PL and thus the bladder is shown in deflated state. At the right hand side of the figure, a front view is given of the gripper finger. In deflated state, the thickness TH of the gripper finger at the bladder height is limited in view of the other dimension, so that the gripper finger 25 is able to easily get between the object and another structure as will be explained with reference to Fig. 7.

Fig. 6 depicts a gripper finger GF1 comprising a plate PL and a bladder BL forming membrane ME which is sealed around its edges except at the top side where it is connected 30 to a tube TU to inflate or deflate the bladder BL. At half the height of the bladder movement of the membrane is limited by a cross-bar CB, so that when the bladder is inflated as shown on the left hand side of the figure, two cushions CU1, CU2 are formed to engage with an object, whereas in Fig. 5 only one cushion is formed by inflating the bladder BL. In the middle, the bladder BL is connected to vacuum so that the membrane is lying against the 35 plate PL and thus the bladder is shown in deflated state. At the right hand side of the figure, a front view is give of the gripper finger. The cross-bar can also be used as an abutment for objects so that objects are effectively gripped at the abutment and the cushions CU1, CU2 - 12- stabilize the gripping operation and prevent the object from moving relative to the gripper finger.

Fig. 7 depicts a conveyor CON on which objects OB can be transported. The conveyor 5 comprises on each side a guide GU to prevent the objects from falling sideways from the conveyor CON. A gripper assembly GA is provided to grip the objects and transport them to another location, e.g. another conveyor or a packaging station. The gripper assembly has two gripper fingers GF1, GF2 which may be configured similarly as the gripper fingers in any of the figures 1-3, 5, 6. These gripper fingers have in common that their thickness is limited 10 so that they fit in between the objects and the guides and therefore a compact conveyor can be used in combination with the gripper assembly.

Fig. 8 shows three objects OB1, OB2, OB3, here depicted as three sweet peppers, which are transported along a conveyor (not shown) and their mutual positions and orientations.

15 Indicated in Fig. 8 is a centerline CL which corresponds to the middle of the conveyor and to the centre of the gripper assembly which will be explained below.

A sensor system, e.g. a camera system, is provided above the conveyor to measure the position of the objects relative to each other and the dimensions. This results in the following 20 information: Y1 the length of object OB1; Y2 the length of object OB2; Y3 the length of object OB3; X1 the width of object OB1; 25 X2 the width of object OB2; X3 the width of object OB3.

From the length and width information a centre C1, C2, C3 of each object OB1, OB2, OB3 can be defined which is halfway the length and width of the respective object. The sensor system is then also able to determine the position of these centers relative to each other and 30 relative to the centre line CL and thus yields the following information: dX1 distance from centre C1 to centerline CL; dX3 distance from centre C3 to centerline CL; dY1 distance between centre C1 and C2 in a direction parallel to centerline CL; dY3 distance between centre C2 and C3 in a direction parallel to centerline CL.

35 It is mentioned here that the distance of centre C2 to centerline CL is zero so that no corresponding dX2 is indicated.

- 13-

It is further possible to determine the orientation of the objects, thereby determining the position of a stalk ST of each sweet pepper. As a result, measures can be taken to avoid that the sweet pepper is gripped at the stalk ST, e.g. by rotation of the corresponding gripper. As there are no problematic orientations in this example, this possibility is not 5 described in more detail.

The three sweet peppers will be packaged together and therefore a gripper assembly is provided with three pairs of gripper fingers GF1 ,GF2,GFT,GF2’,GF1”,GF2” (see Fig. 9) forming three gripper finger pair units U1 ,U2,U3. Each pair will grip one of the objects. The 10 gripper fingers are moveable in a horizontal direction perpendicular to the center line in a similar manner as in Fig. 4 so that when a centre of a space in between the gripper fingers is aligned with the centerline CL, said alignment is not affected by subsequent movement of the gripper fingers relative to a frame. A gripper finger pair unit can also be translated as a unit in a horizontal direction parallel to the centerline and independently of the other gripper 15 finger pair units.

First, the gripper fingers are positioned around the objects based on the information of the sensor system. The result of this positioning is shown in Fig. 9. Positioning is preferably done in such a way that the distance to the object is small enough to allow to quickly grip the 20 object.

As the objects OB1 and OB3 are not aligned with the centerline CL, the distance between the object and the respective gripping fingers is not equal to each other. Each gripper finger is provided with an inflatable bladder BL as shown in Fig. 10 to grip the respective object in 25 between the gripper fingers. When the bladders are inflated simultaneously for objects OB1 and OB3, one of the bladders will come into contact with the respective object earlier than the other bladder which will disturb the position of the respective object and may result in the loss of information on position, orientation and/or one or more dimensions of the object. To overcome this problem, the inflation of the bladders is timed such that the bladders come 30 into contact with the object simultaneously and grip the object without disturbing or changing the position of the object as shown in Fig. 10. Due to this gripping operation, the orientation of the objects is frozen and the objects can subsequently be positioned in a controllable manner for packaging reasons.

35 By inflating the bladders of a finger gripper pair unit to the same extent, the bladders will automatically align the objects with the centerline at the end of the inflation sequence. Subsequently, the gripper units can be displaced in a direction parallel to the centerline to - 14- adjust the distance between the objections in said direction. This end result is shown in Fig.

11. The objects together can be placed in a packaging station to be packaged and are then already in the right positions which saves a lot of time.

5 Fig. 12 depicts a gripper assembly according to a further embodiment of the invention. The gripper assembly comprises two gripper fingers GF1 ,GF2 arranged opposite to each other. Each gripper finger comprises a plate as gripper finger body that is covered by a membrane to form an inflatable bladder BL. The width of the gripper fingers is such that three objects OB1 ,OB2,OB3 can be gripped at the same time. Although not shown, the three objects may 10 be packaged together in foil or a plastic cover and be subsequently handled by the gripper assembly without damaging the packaging material or the objects.

Fig. 13 depicts schematically a handling system HS according to an embodiment of the invention in side view. The handling system comprises a conveyor CON for conveying 15 objects OB in a conveying direction COD. The system HS further comprises a gripping device GRD having a motion device MD with gripper assembly GA according to the invention to displace the objects from the conveyor to another location, e.g. another conveyor or a packaging station.

20 A sensor system MES is provided to measure the position and one or more dimensions, and possibly orientation, of the conveyed objects OB prior to being engaged by the gripping assembly GA. A control system COS is provided to control the gripping device based on input of the sensor system MES.

25 Fig. 14 depicts a gripper finger for a gripper assembly according to the invention, comprising a gripper finger body RB in the form of a rectangular box having an opening on the front side which is covered by a membrane ME to define an inflatable bladder, the box being connected to a medium supply via a conduit CO to inflate the bladder. The other sides of the box are rigid.

30

Claims

A gripper assembly for manipulating a variably shaped object, comprising: 5. a frame; - two gripping fingers, wherein each gripping finger has a gripping finger body connected to the frame, and wherein each gripping finger is provided with at least one inflatable blister which is active in a space between the at least two gripping fingers, and wherein the blister is arranged on to grasp the object, characterized in that at least one, preferably all, gripping finger bodies are mounted on the frame movably, preferably translatable, and that the gripper assembly comprises actuating means for moving the gripping finger bodies of the at least two gripping fingers to adjust the size of the space between the at least two gripping finger bodies in addition to inflating the blister.

A gripper assembly according to claim 1, wherein the actuating means are adapted to keep the center of the space between the at least two gripping finger bodies constant with respect to the frame in at least one horizontal direction.

A gripper assembly according to claim 1 or 2, wherein a single pair of gripper fingers are provided that are positioned opposite each other to receive the object between the gripper finger pair.

4. A gripper assembly according to claim 3, wherein the frame supports a plurality of gripping finger pairs, each pair belonging to a separate space for receiving an object to be gripped, each pair forming a gripping finger pair unit and being arranged to hold an object between the respective gripping finger pair and wherein the actuating means are adapted to move the grasping finger bodies of a grasping finger pair toward or away from each other in a grasping direction independently of one or more of the other grasping finger pairs.

A gripper assembly according to claim 4, wherein gripping units are mounted on the frame to be movable relative to each other - as a unit.

A gripper assembly as claimed in one or more of claims 1-5, wherein each gripping finger extends in the vertical direction and has a height and width that is much greater than a thickness of the gripping finger.

A gripper assembly according to claim 6, wherein each gripping finger body is formed by a box with an opening on one side covered by a membrane for defining the inflatable blister, the box being connected to a fluid supply for inflating the blister .

8. A gripper assembly as claimed in claim 6, wherein each gripping finger body is formed by a plate, e.g. a flat plate, which is covered with a membrane sealed at the edges thereof for defining an inflatable blister, and wherein a medium supply is present is to introduce medium between the plate and the membrane to inflate the blister.

9. A gripper assembly as claimed in one or more of claims 1-8, comprising a fluid supply with a cylinder and a piston movable in the cylinder so that there are two separate chambers in the cylinder separated by the piston, and wherein the at least one blister of the gripping fingers is in contact with one of the chambers of the cylinders, and wherein the chamber is filled with a medium such that movement of the piston in the cylinder is capable of inflating or deflating the blister .

A gripper assembly as claimed in one or more of claims 1-8, comprising a fluid supply having a chamber connected to a high-pressure fluid source and to at least one of the blisters of the gripping fingers, a valve being disposed between the chamber and the at least one blister, and wherein the at least one blister is also connected to a low pressure environment via a valve.

A manipulation system for manipulating variably shaped objects, comprising: - a conveyor belt for conveying the objects in a conveying direction; - a gripping device comprising a moving device with a gripper assembly according to one or more of the claims 1-10 for moving the objects of the conveyor belt to another location, e.g. a different conveyor belt or a packaging location; - a sensor system for measuring the position and one or more dimensions of the transported objects before they come into contact with the gripper assembly; and 30. a control system for controlling the gripping device based on input from the sensor system.

12. A manipulation system as claimed in claim 11, wherein the gripper assembly comprises a plurality of gripping units with associated gripping fingers, and wherein the control system is arranged to simultaneously grip a plurality of objects without changing the orientation and position of the objects and subsequently, after gripping, the relative positions between change the multiple objects, for example for packaging reasons.

13. A method for gripping a variably shaped object from a conveyor belt with a gripper assembly according to one or more of the claims 1-8, comprising the following steps: a. Measuring the position and outer dimensions of the object on the conveyor belt ; b. positioning the gripping fingers at a predetermined distance from the outer periphery of the object; c. inflating the blisters of the gripping fingers so that the blisters come into contact with the object simultaneously without moving the object, whereby the object is caught between the gripping fingers.

A method according to claim 13, wherein after step c. the blisters are inflated such that the object is centered between the grasping fingers.

A method according to claim 13 or 14, wherein the gripper assembly is according to claim 5, and wherein each object is gripped according to claim 14 or 15 and 15 wherein the gripping units are subsequently moved to position the objects relative to each other, e.g. for packaging reasons.