Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J15/00—Gripping heads and other end effectors
  • B25J15/0023—Gripper surfaces directly activated by a fluid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J15/00—Gripping heads and other end effectors
  • B25J15/02—Gripping heads and other end effectors servo-actuated
  • B25J15/0253—Gripping heads and other end effectors servo-actuated comprising parallel grippers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
  • B65G47/00—Article or material-handling devices associated with conveyors; Methods employing such devices
  • B65G47/22—Devices influencing the relative position or the attitude of articles during transit by conveyors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
  • B65G47/00—Article or material-handling devices associated with conveyors; Methods employing such devices
  • B65G47/22—Devices influencing the relative position or the attitude of articles during transit by conveyors
  • B65G47/26—Devices influencing the relative position or the attitude of articles during transit by conveyors arranging the articles, e.g. varying spacing between individual articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
  • B65G2201/00—Indexing codes relating to handling devices, e.g. conveyors, characterised by the type of product or load being conveyed or handled
  • B65G2201/02—Articles
  • B65G2201/0202—Agricultural and processed food products
  • B65G2201/0211—Fruits and vegetables

Definitions

• 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 bodies, said bladders being adapted to grip an object.
• 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 finger.
• the bladder can be inflated, thereby decreasing the effective distance between the gripper fingers.
• the bladders can be deflated.
• an object positioned in a space between the gripper fingers can be gripped or released respectively.
• a disadvantage of this known gripper assembly is that when variable-shaped objects, such as sweet peppers, have to be gripped, the time it takes 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.
• a gripper assembly according to the preamble of claim 1 , 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 and deflation of the bladders.
• 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.
• 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.
• 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 assembly.
• a gripper finger body In addition to deflation of the bladder, a gripper finger body can be retracted to quickly release the gripper finger from the object.
• the moveability of the gripper finger bodies also allows to inflate the bladders prior to gripping in which gripping is subsequently performed by moving the gripping fingers towards each other.
• 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 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.
• 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 between the at least two gripper fingers is large enough to receive the object - and does not require positioning of the frame in dependency of the actual position of the centre of the space determined by the mutual position of the gripper fingers, thereby simplifying the control of the gripper assembly. In other words, the positioning of the centre of the space is decoupled from the positioning of the gripper fingers.
• the gripper assembly has a single pair of gripper fingers provided opposite each other to receive the object in between the pair of gripper fingers.
• the use of two gripper fingers is sufficient to controllably grip an object, especially as the inflatable bladder in inflated state may more or less encompass portions of the object which provides a stable gripping operation.
• the bladders are preferably larger in at least one dimension than the corresponding dimensions of the largest object being handled by the gripping assembly.
• This also has the advantage that the pressure inside the bladder may not increase above a predetermined value in case the largest object that can be handled is handled. In case the bladder is smaller than the largest object and the largest object is gripped, the bladder may not expand as much as designed which could result in a too large pressure increase inside the bladder.
• the same advantage of keeping the pressure below a predetermined value may also be obtained by providing a resilient tube member in the tubes supplying the pressure to the bladder, because then if the bladder is not able to fully expand, the resilient tube member may expand instead to keep the pressure within limits.
• the gripper assembly comprises a frame supporting multiple pairs of 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 fingers.
• 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.
• 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.
• the gripping finger pair units are arranged on the frame in a row.
• the gripping finger pair units may be moveable in a direction parallel to the row, so that the mutual distance between the gripping finger pair units can be adjusted.
• the gripper fingers of each gripping finger pair units are positioned or positionable at opposite sides of the row, such that the respective gripper finger bodies are moveable in a direction perpendicular to the row with respect to each other in order to be able to adapt the size of the space in between the gripper finger bodies in addition to inflation and deflation of the bladder.
• the gripper finger pair units may be arranged on the frame in a two- dimensional array.
• the desired array pattern may depend on the goal of the gripping action, for instance on the packaging requirements.
• the gripper assembly cooperates with a conveyor system which conveys objects in a conveyance direction.
• the objects to be gripped from the conveyor system are substantially positioned on the conveyor system in accordance with the arrangement of the gripping finger pair units.
• the objects may be conveyed in a row-like manner in case the gripper finger pair units are arranged in a one-dimensional or two-dimensional array.
• the row may extend in conveyance direction while gripping objects from the conveyor system or may extend in a transverse direction perpendicular to the conveyance direction while gripping objects from the conveyor system.
• the required moveability of the gripping finger pair units may depend on the manner in which the objects are supplied to the gripping finger pair units.
• the objects may be conveyed along a conveyer system towards the gripping finger pair units, wherein the objects that are simultaneously gripped by the gripping finger pair units are aligned with respect to each other in a horizontal direction and/or are positioned in a desired angular orientation.
• the gripping finger pair units may only have to position the objects relative to each other in other degrees of freedom if necessary.
• the gripper assembly may have a lower weight as less actuators are required.
• a lower weight of the gripper assembly has the advantage that the obtainable speed of the gripper assembly can be increased.
• the weight of a gripping finger pair unit is about 1 -2 kilograms.
• Alignment of the objects may for instance be achieved by a conveyer system having product carriers with an upper surface for carrying the object, wherein the carried object is freely moveable over the upper surface, and wherein the upper surface has a centre position, said conveyer system further having a centring unit for positioning an object on the product carrier at the centre position, so that the gripper assembly only has to align the centre of the space between the gripper fingers with the centre position of the product carrier in order to reliably grip the object from the product carrier.
• the desired angular orientation may for instance be obtained by using a detector for determining an initial angular orientation of the object on a product carrier as described above, using a control unit to determine a deviation angle which is defined by a deviation of the initial angular orientation from the desired angular orientation, and operating a rotation unit to rotate the product carrier about the deviation angle.
• 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 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.
• each gripper finger has a flat plane configuration when the bladder is deflated.
• the flat plane configuration in combination with the bladders has the advantage that when gripping and releasing an object, the gripper fingers do not require a lot of space, also because the gripper fingers do not have to be retracted from the object as this is effectively done by deflating the bladders. This allows to use the gripper fingers in tight spaces. It further allows the gripper assembly to be used in combination with sidewall structures, e.g. sidewall structure of another conveyer, wherein the object is placed in between the sidewall structures by the gripper assembly, and wherein the sidewall structures limit the movement of the placed object, thereby ensuring that the position and/or orientation of the object after placement can not change such that subsequent operations fail and thus improves the reliability of the total handling of the object.
• sidewall structures e.g. sidewall structure of another conveyer
• 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 in a gripped state is possible without interference between gripper fingers of adjacent gripper finger pair units. It is envisaged that other widths and sizes of the gripper fingers may also be suitable depending on the application.
• the height of the bladder is larger than the largest object to be handled by the gripping assembly.
• the bladder is connected to the gripper finger body at a centre region only which allows the bladder to bulge outwards during inflation and thereby encompass the gripped object, i.e. a portion of the bladder is able to get below or above the object.
• the bladder is limited in its movement and will not bulge outwards as much as when the bladder is not connected to the gripper finger body as more deformation of the bladder is allowed.
• the bladder is formed by a closed pouch having holes as in- and outlet to allow air to controllably flow in and out of the pouch via the gripper finger body.
• the side of the pouch facing towards the gripper finger body is only attached to the gripper finger body in a centre region, so that peripheral regions of the pouch are free from the gripper finger body and due to their deformability are able to more or less encompass an object upon inflation.
• the size of the pouch in vertical direction is larger than the largest object that is gripped by the gripper assembly.
• the pouch is filled with a porous layer to prevent the sidewalls of the pouch to contact each other when deflating. This is especially advantageous in case of quickly deflating the pouch using vacuum and ensures that all air is removed from the pouch.
• 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.
• a medium supply i.e. a source of medium, e.g. a gas or a fluid
• the 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.
• each gripper finger body is formed by a plate, e.g. a planar plate, covered 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 or pouches may comprise elastic, e.g. elastomeric, material.
• An 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.
• the membrane is thin to minimize the stresses in the material and improve the deformability and flexibility of the membrane such that inflating the bladder and encompassing portions of the object can then be done using a relatively low pressure in the bladder.
• the gripper finger bodies comprise a porous material as a spacer for the bladder, so that deflating the bladder, e.g. due to connecting the bladder to vacuum, will not damage the bladder as the moveability of the bladder is limited by the porous material.
• 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 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 be supplied to the bladder in a controlled, reproducible and quick manner.
• 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 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.
• a medium supply allows to inflate and deflate the bladder by performing the following steps for inflating:
• the chamber is 40ml in volume and the high pressure source provides 7 bar of pressure. It is possible that each bladder of a gripper finger is connected to a separate medium supply 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.
• 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 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.
• a gripper assembly for handling a variable-shaped object, comprising a frame and two gripper fingers, each gripper finger having a gripper finger body that is mounted to said frame, wherein each gripper finger is provided with at least one inflatable bladder that is effective in a space in between the two gripper fingers, said bladder being adapted to grip the object and to be inflatable in an inflating direction towards the space in between the two gripper fingers, wherein the gripper finger bodies have a dimension in the inflating direction that is at least five times, more preferably at least ten times, smaller than any of the other two dimensions.
• the gripper finger bodies are able to penetrate tight spaces compared to the size of the object to be gripped while still being able to grip and release the object, because the bladder does not necessarily require the gripper finger body to move for gripping and releasing.
• the dimension of the gripper finger body in the inflating direction is at most 10mm, preferably at most 5mm, more preferably 3-4mm.
• the mechanical connections between gripper finger body and frame and the tubing towards the bladder are provided at the side of the gripper finger body facing towards the frame, e.g. at the side extending parallel to the inflating direction.
• the invention also relates to handling system to handle variable-shaped objects, comprising:
• a gripping device having a motion device with a gripper assembly according to the first or second aspect of the invention to displace the objects from the conveyor to another location, e.g. another conveyor or a packaging location;
• control system to control the gripping device based on input of the sensor system.
• the other conveyor or packaging location is also part of the handling system, wherein the conveyor or packaging location comprises sidewall structures, wherein the control system is configured to place objects in between the sidewall structures by a gripping device with a gripper assembly according to a second aspect of the invention.
• An advantage of this embodiment is that the dimensions of the gripper finger bodies of the gripper assembly allows the sidewall structures of the other conveyor or packaging location to be positioned close to the objects thereby preventing the objects to undesirably change position and/or orientation after placement.
• the sensor system is able to provide information which can be used by the control system to control the gripping device.
• the control system is adapted to control operation of the actuation means in order to move the moveable gripper finger bodies based on position and/or dimensional information from the sensor system.
• the sensor system can be for instance an optical system, i.e. a visual system using one or more cameras.
• the sensor system is able to measure the orientation of the objects, and 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 a protrusion 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 relative to the object.
• the gripper assembly comprises multiple gripper units with corresponding gripper fingers
• the control system is configured to simultaneously grip multiple objects without changing the orientation and position of the objects. Subsequently after gripping, the relative positions between the multiple objects may be changed, 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 may be altered in an open loop manner, i.e. without requiring additional measurements on the position.
• information about one or more dimensions of the object is used to position the gripper fingers of each gripper unit such that upon inflation, each object is gripped substantially simultaneously and with substantially the same gripping force.
• 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:
• 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 position information is lost during gripping.
• the bladders are eventually inflated to an equal extent, so that after gripping the object is automatically centred between the gripper finger bodies.
• 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: a) measuring the position and one or more dimensions of three sweet peppers on the conveyor;
• the two gripper fingers are arranged at opposite side of said line.
• the gripper finger pair units are rotatable about a vertical axis, so that the method further comprises the steps of:
• the invention also relates to a method for handling multiple objects at the same time using a gripper assembly according to a first or second aspect of the invention, said method comprising one or more of the following steps
• each product carrier has an upper surface for carrying an object, wherein the carried object is freely moveable over the upper surface, and wherein the upper surface has a centre position
• the mutual distance between the objects is adjusted by the gripper assembly during transferring of the objects to the packaging line or location.
• the packaging line or location is provided with sidewall structures, wherein the objects are positioned in between the sidewall structures by the gripper assembly, and wherein the gripper assembly is preferably according to the second aspect of the invention to allow the sidewall structures to be provided at a relatively small distance to the objects.
• Fig. 1 depicts schematically a gripper assembly according to an embodiment of the
• 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.
• 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 state and in front view;
• Fig. 7 depicts a conveyor and a part of a gripper assembly according to yet another
• Fig. 8 depicts three objects in an exemplarily situation of how they can be positioned on a conveyor
• Fig. 9-1 1 depict a method to grip and position the three objects of Fig. 8;
• Fig. 12 depicts a gripper assembly according to a further embodiment of the invention.
• Fig. 13 schematically depicts a handling system according to an embodiment of the
• Fig. 14 depicts a gripper finger for a gripper assembly according to another embodiment of the invention.
• Fig. 15 depicts a gripper finger for a gripper finger assembly according to yet another
• Fig. 16A shows in a schematic view a first and a second stage I, II of a preferred
• Fig. 16B shows in a schematic top view a conveyor system according to 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.
• 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.
• 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.
• each cylinder CY comprises a piston PI dividing the interior of the cylinder into two chambers CH 1 ,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.
• One of the chambers of the cylinder CY (chamber CH1 ) is in fluid communication with the respective bladder BL via a hole/opening in the plate PL and a conduit CO extending from the chambers CH 1 to the respective holes.
• the chambers CH 1 and respective conduits CO are filled with a medium, e.g. air or another suitable fluid.
• the medium is preferably in the gas phase.
• 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 without touching the gripper fingers.
• An advantage of the bladders is that the bladder is able to adapt its shape to the outer contour of the object 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 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.
• the frame and the actuation members are omitted for simplicity reasons.
• FIG. 1 and 2 also shows a gripper assembly according to a first aspect of the invention.
• the first and second aspect may also be separately implemented from each other.
• the actuators AM may be omitted, thereby decreasing the weight of the gripper assembly and increasing the obtainable speed of the gripper assembly.
• the volume used to inflate the bladders should be sufficient to grip the object.
• the volume may be adapted to the size of the object in order to keep the gripping force within a predetermined range, because a too low gripping force will result in a badly gripped object which may fall due to gravity forces, and a too high gripping force may damage the object, especially when the object is a horticultural object.
• 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 CH 1 via a valve V1 and to a low pressure environment LPE, preferably vacuum, via a valve V2.
• the chamber CH1 is connected to a high-pressure source HPS, e.g. compressed air, via a valve V3. This allows for the following inflation procedure:
• valve V1 ,V2,V3 are closed; subsequently valve V3 is opened to allow medium from the high-pressure source HPS into the chamber CH1 ;
• valve 3 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 CH 1 into the bladder BL;
• valve V1 when an equilibrium is reached, valve V1 is closed and valve V3 can be opened to fill the chamber CH 1 again with medium for a next inflation cycle.
• 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.
• the above inflation and deflation procedures can be performed at any time to grip or release an object.
• the degree of inflation can be regulated.
• this can for instance be done by regulating the piston PI or by adapting the pressure inside chamber CH 1 .
• this can for instance be done by adjusting the time a valve is opened or closed or by adjusting the pressure inside the chamber CH 1 .
• the pressure inside the chamber CH 1 is 7 bars.
• the volume of the chamber CH 1 in Fig. 3 may be 40 ml.
• An advantage of the inflation procedure of fig. 3 is that inflation can be done quickly and reproducibly. Deflation can also be done quickly, especially when the low-pressure environment is vacuum.
• Fig. 4 depicts schematically a gripper assembly GA according to yet another embodiment of 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.
• the moveability of the gripper fingers is indicated by the arrows AR.
• 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.
• 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 of frame FR.
• the endless belt EB is driven by a motor MO which drives pulley PU2 via belt BE.
• the left gripper finger GF1 is connected to the upper part UP of the endless belt EB via attachment member AB1
• the right gripper finger GF2 is connected to the lower part LP of the endless belt EB via attachment member AB2.
• 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 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 members GE1.GE2.
• a tubing TU per bladder is provided, which tubing is provided parallel to the gripper finger and at the upper side of the bladder, thereby occupying minimal space in the gripping direction so that the gripper fingers can be flat to be moved in tight spaces.
• the tubing TU is only partially shown, but will connect to a chamber via the frame (see for an explanation on how to inflate and deflate the bladder the description corresponding to the figs 1 -3).
• 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.
• the bladder BL is filled with medium so that the bladder is shown in inflated state.
• 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.
• a front view is given of the gripper finger.
• the thickness TH of the gripper finger at the bladder height is limited in view of the other dimension, so that the gripper finger 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 to a tube TU to inflate or deflate the bladder BL.
• a cross-bar CB 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 CU 1 , CU2 are formed to engage with an object, whereas in Fig. 5 only one cushion is formed by inflating the bladder BL.
• 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.
• 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 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 comprises on each side a guide GU to prevent the objects from falling sideways of the conveyor CON.
• the guide is in this embodiment a sidewall structure.
• 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 with respect to other dimensions, 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.
• the thickness i.e.
• the dimension in the gripping direction in deflated state is preferably at least five times smaller, more preferably at least ten times smaller than any of the other dimensions.
• the thickness is preferably at most 10mm, more preferably at most 5mm and most preferably in the range of 3-4mm.
• the guide GU can be positioned close to the object as shown in fig. 7, so that the moving range of the object towards the guide is limited, while still being able to place objects on the conveyor with the gripper assembly. Hence, the position of the object in a direction towards the sidewall structures can be guaranteed, which may be advantageous for operations carried out on the objects after placing them on the conveyor. The same principle can be applied at a packaging location without having a conveyor. Fig.
• 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.
• a centerline CL which corresponds to the middle of the conveyor or a conveyor part, 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 may result in the following information:
• the information may be obtained from a 2D camera system, but preferably the camera obtains 3D information, i.e. including height information, so that the dimensions and possibly the orientation of the object can be obtained more accurately and reliably.
• 3D information allows for instance to more accurately determine the orientation of lobes on a pepper of a paprika from which the angular orientation can be derived.
• the 3D information may be obtained using a laser scanner, which preferably emits a laser line to move across the object, and which determines the height at which the laser line reflects by measuring the position of an image of the laser line in an image taken by a separate camera, i.e. laser triangulation.
• the time it takes for a laser spot to travel to the object and travel back to the detector may be used to determine the distance or mimicking stereopsis may be used to obtain 3d 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 relative to the centre line CL and thus yields the following information:
• a gripper assembly is provided with three pairs of gripper fingers GF1 ,GF2,GF1 ',GF2',GF1 ",GF2" (see Fig. 9) forming three gripper finger pair units U1 ,U2,U3.
• the 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 finger pair units. The moving range in the horizontal direction parallel to the centerline may be limited by the position of adjacent gripper finger pair units to avoid collisions.
• the gripper finger pair units may be rotatable about an axis perpendicular to the centerline and the gripping direction, which axis is perpendicular to the plane of drawing in Fig. 8-1 1 .
• 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 object.
• Each gripper finger is provided with an inflatable bladder BL as shown in Fig. 10 to grip the respective object in between the gripper fingers.
• 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.
• the inflation of the bladders is timed such that the bladders come into contact with the object simultaneously and grip the object without disturbing or changing the position of the object as shown in Fig. 10.
• the orientation of the objects is frozen and the objects can subsequently be positioned in a controllable manner for packaging reasons.
• the different timing of respective bladders may not be required, but the gripper fingers may still be positioned differently for each object in order to simultaneously grip all objects and/or to grip each object with substantially the same gripping force.
• Fig. 1 1 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 adjust the distance between the objections in said direction. This end result is shown in Fig. 1 1 .
• 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.
• 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.
• the three objects may 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 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.
• 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.
• Fig. 14 depicts a gripper finger for a gripper assembly according to an embodiment of 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.
• Fig. 15 depicts a cross section of a gripper finger for a gripper assembly according to yet another embodiment of the invention.
• the gripper finger comprises a rigid gripper finger body RB, which has a box-like shape with one side being formed by a flexible membrane ME and the other sides being rigid. Attached to the membrane is a closed pouch PO, which pouch is formed by two flexible layers attached to each other at the periphery of the layers. The pouch is only connected to the membrane in a centre region CR. At the centre region CR, one or more holes HO are extending through the membrane and through the layer of the pouch that is attached to the membrane to allow fluid to be introduced into the pouch and to allow fluid to be drained out of the pouch.
• the pouch thus forms a bladder BL of the gripper finger which can be inflated and deflated to respectively grip and release an object OB, which object is only partially shown.
• the deflated state of the pouch is shown on the left in Fig. 15 and the inflated state is shown on the right.
• the pouch In the inflated state, fluid medium is introduced into the pouch PO.
• the resulting pressure increase may also deform the membrane ME as is shown.
• the membrane may be replaced by a more rigid element, so that this element will not bulge outwards during inflation.
• the advantage of the pouch being attached to the gripper finger body at the centre region only is that at the upper side and at the lower side of the pouch, the pouch is able to deform more then at the centre region, such that the pouch is able to engage with the upper side and lower side of the object, thereby more or less encompassing the object.
• the height of the pouch is preferably chosen such that it is always larger than the object to be handled, so that the pouch is always able to deform at the upper or lower side thereby preventing the pressure inside the pouch from getting too high.
• the pouch comprises an internal porous layer which prevents the outer layers of the pouch of contacting each other, i.e. the porous layer is a porous spacer. This ensures that during deflation all fluid medium is sucked out of the pouch.
• a porous layer POL is shown as a dashed line in the left figure of fig. 15 only.
• Fig. 16A shows in a schematic view a first and a second stage I, II of a preferred method according to the invention for processing conveyed objects 1 in a conveyor system.
• objects 1 are supplied which are loaded in a random orientation on product carriers 2.
• the objects 1.1 , 1 .2, 1.3 are displaced to a centre position 21 of the product carriers 2.
• the objects 1.1 , 1 .2, 1 .3 are centred on the product carriers 2 at the centre position 21 .
• the centred objects 1 are rotated by rotating the product carriers 2 about the centre position 21 to a predetermined orientation.
• the objects are repositioned into a predetermined orientation.
• the objects can be processed further, e.g. be gripped by a gripper assembly according to the invention.
• the gripper assembly can efficiently grip the objects without requiring a lot of alignment of the gripper fingers relative to the objects, which results in a fast and efficient gripping process.
• the gripper assembly may further require less degrees of freedom as the objects are already aligned on a centreline as referred to in figs 8-1 1 and are already rotated to the correct rotation. The remaining degree of freedom may be to adapt the distance between the objects as shown in Figs. 8-1 1 .
• Other degrees of freedom may be provided by a motion device, which for instance allows to move the gripper assembly with the same velocity as the conveyor system, so that the gripper assembly is substantially stationary relative to the objects to allow gripping.
• Fig. 16B shows in a schematic top view an embodiment of a conveyor system 10 according to the invention.
• the shown portion of the conveyor system is in this embodiment an upper horizontal section of an endless conveyor system.
• the conveyor system 10 is arranged to convey objects in a conveying direction 9.
• the conveyor system 10 has a supplier unit 300 for supplying objects 1 to product carriers 2.
• the objects are food articles like snacks or vegetables.
• the objects are in this embodiment peppers of a paprika, which are known to have an amorphous shape.
• the objects are conveyed along at least one operation unit 400 for carrying out an operation.
• the conveyor system in this embodiment is provided to operate at least two objects together at the operation units.
• the conveyor system may be arranged for packaging objects.
• the at least two objects may be gripped together by a gripper assembly according to an embodiment of the invention to pack the objects in one step in a package.
• the supplier unit 300 has at least two, in particular three supplier devices 300.1 , 300.2, 300.3 for supplying the objects to at least two, in particular three product carriers 2.1 , 2.2, 2.3.
• the product carriers 2 are arranged side by side on a base carrier 3.
• the conveyor system 10 is a multiple track conveyor system.
• the multiple track conveyor system comprises at least two, in particular three product tracks, travelling in an endless manner through the conveyor system.
• the product carriers are conveyed about the three product tracks in a conveying direction 9 by the base carrier 3 along the upper horizontal section.
• the base carriers 3 are coupled to each other in an endless manner, but may alternatively or additionally be mounted to a conveyor belt, in this case an endless conveyor belt. At the end of the endless conveyor system near operation unit 400, the base carriers are transferred to a corresponding lower horizontal section to be transported back to the beginning of the upper horizontal section near supplier unit 300.
• the product carriers have an outer dimension of at most 50cm, in particular at most 30cm.
• the product carriers have an outer dimension of at least 10cm, in particular at least 15cm.
• the multiple track conveyor system may have an outer dimension of at most 3 metres, in particular at most 2 metres, wherein the outer dimension is defined as the dimension of the conveyor system in conveyance direction 9.
• the supplier unit 300 supplies objects from above to the product carriers 2.
• the objects are in random orientation and at a random position supplied to an upper carrying surface of the product carrier 2.
• the supplied objects can freely move over the upper surface of the product carrier.
• the objects are positioned in a preparing step by a centring unit 100 and a rotation unit 200 before supplying the objects to an operation unit 400. In the centring unit 100, the objects are moved to a centre position of the product carrier.
• Fig. 16B shows a first operation unit 400.
• the first operation unit 400 is a handling unit.
• the handling unit comprises a gripper assembly for gripping at least two objects from at least two product tracks in one gripping step. The objects are gripped together.
• An advantage of the centring unit and the rotation unit is that the objects are always supplied to the handling unit 400 in a predetermined orientation and position, so that the handling unit can easily and reliably handle the objects.
• the handling unit comprises a gripper assembly with gripper finger pair units
• the predetermined orientation and position may have the advantage that the gripper finger pair units need less degrees of freedom thereby reducing the weight of the gripper assembly and thus increasing the obtainable speed of the handling device.
• the distance between the objects may be adjusted to prepare the objects for packaging.
• the centring unit, rotation unit and the handling unit are able to package amorphous objects such as peppers of a paprika, wherein each pepper usually has a different size and shape, in an efficient and fast way without damaging the peppers during handling/operation of the peppers.
• the first operation unit 400 preferably comprises a gripper assembly configured to transfer the objects to a packaging line or location, e.g. according to fig. 7, after which the objects are packaged together.
• the rotation unit 200 comprises a detector 201 for observing an initial angular orientation of supplied objects.
• the product carrier is conveyed in a conveying direction along the detector to determine the initial orientation of the supplied objects.
• the initial orientation may differ from the desired orientation.
• the desired orientation may for instance be determined by the stem of a fruit if present.
• An example of a desired orientation is that the stems should be positioned on the left or right side of the object as seen in conveyance direction 9.
• a control system in particular a computer, is implemented to calculate a deviation angle which is defined by the difference between the desired and initial angular orientation.
• the deviation angle determines an angle of rotation which has to be performed by the rotation unit 200.
• the conveyor system 10 may comprise an auxiliary detector 203.
• the auxiliary detector is positioned downstream the conveying direction after the rotational element 202.
• the auxiliary detector 203 is used to control the desired orientation of the object.
• the auxiliary detector 203 is used to generate data relating to a secondary angular deviation.
• the data from the auxiliary detector is used to fine tune an upstream rotation element 202 to obtain a more accurate orientation.
• the rotation element may be automatically controlled in a closed loop.
• the auxiliary detector 203 may advantageously be used to determine whether the objects are ready for handling by the operation unit 400 as shown in Fig. 16B. For instance, if the desired orientation is a sideways extending stem from the object, but the stem is facing upwards, rotation of the object in the rotation unit will not move the object to the desired orientation. In fact, it may not be possible at all to get the object into the desired orientation. Hence, this can be detected by the auxiliary detector 203 and based on the output it may be decided to skip operation on the objects by the operation unit and transport the objects to a waste or storage location. Further, the auxiliary detector may be used to detect a malfunction in the detector 201 or the rotation unit 200.
• the auxiliary detector 203 may further be used to control the operation unit in relation to the detected position and orientation of the objects. For instance, the sideways orientation of the stem on a object may be necessary in order to avoid contact between stem and gripper fingers of a gripper assembly, which gripper fingers may have bladders to grip the objects without exerting too much pressure, and which can be damaged by the stems of the objects. If in an
• the gripper fingers are rotatable as a unit about a vertical axis which allows to adapt the position of the gripper fingers to the orientation of the objects, damage may be prevented.
• the auxiliary detector may further be used to adjust the distance between gripper fingers of a gripping assembly to the size of the object to be gripped in order to ensure that the objects can be gripped substantially simultaneously and/or the gripping force is kept below a predetermined value.

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• 2011
  • 2011-11-18 EP EP11790680.0A patent/EP2661337A2/de active Pending
  • 2011-11-18 WO PCT/NL2011/050789 patent/WO2012093932A2/en active Application Filing
  • 2011-11-18 EP EP11788609.3A patent/EP2661404A1/de not_active Withdrawn
  • 2011-11-18 WO PCT/NL2011/050790 patent/WO2012093933A1/en active Application Filing

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