WO2025099258A1

WO2025099258A1 - A gripper and a method of orienting an object by the gripper

Info

Publication number: WO2025099258A1
Application number: PCT/EP2024/081705
Authority: WO
Inventors: Jens Kongensholm Dalgaard; Stef NOOIJEN; Laurens Christian PHILIPPO
Original assignee: Marel AS; Marel Poultry BV
Current assignee: Marel AS; Marel Poultry BV
Priority date: 2023-11-09
Filing date: 2024-11-08
Publication date: 2025-05-15
Anticipated expiration: 2026-05-09

Abstract

A gripper (1) and a method of gripping an object (2). The gripper (1) comprises two jaws having leading edges towards each other and being arrangeable in an open or a closed state. A belt extends across the gap between the leading edges. To allow rotation of the object while it is gripped, the gripper comprises a belt pulling structure which can be actuated to pull the belt to thereby cause movement of the belt in a first direction from one of the jaws towards the other jaw.

Description

A GRIPPER AND A METHOD OF ORIENTING AN OBJECT BY THE GRIPPER

FIELD OF THE INVENTION

The present invention relates to a gripper for gripping an object, particularly a food object such as fish, poultry, pork, cattle/beef, or red meat in general, e.g., chicken breast, chicken drumsticks, or meat products. The gripper comprises a base which can be attached e.g ., to a robot or similar manipulator.

A first jaw and a second jaw are mounted on the base and movable between open and closed positions. The gripper further comprises a belt.

The invention further relates to a robot with a gripper, and to a method of orienting an object by the gripper.

BACKGROUND OF THE INVENTION

Grippers of the above stated kind are used inter alia in food processing industries for handling food products such as meat.

W02007093774 discloses a pick and place device for picking up and re-positioning an article carried by a support surface.

Although this pick and place device shows significant advantages over prior art grippers, it may be desired to facilitate precise delivery of the items and particularly to allow precise arrangement and rotation of items to obtain a specific orientation.

Particularly, it may be difficult, by use of existing pick and place devices, to rotate soft or flexible objects tending to stick to the gripper. This may apply to many different types of food objects. Furthermore, it may be difficult to obtain a desired orientation after the delivery.

SUMMARY OF THE INVENTION

It is an object of embodiments of the invention to provide a simple way to reorient objects, and to reorient objects having an indeterminable shape, size, dexterity, or compactness, e.g., food objects. It is a further object to provide reorientation of food objects while they are moved from one location to another location. It is a further object to enable a simple and inexpensive gripper capable of reorienting food objects.

For these and other objects, this disclosure, in a first aspect, provides a gripper for gripping an object.

The gripper comprises a base, a first and a second jaw mounted on the base, and a belt.

Each jaw terminating in a leading edge e.g., an edge pointed towards the other jaw, and at least one of the first jaw and the second jaw is movable relative to the base and relative to the other jaw to arrange the gripper in an open state or a closed state.

A gap between the leading edges is smaller in the closed state than in the open state to thereby allow receiving and holding an object in a space defined by the jaws, more particularly, a space between the jaws.

The belt extends across the gap between the leading edges, and the gripper further comprises a belt pulling structure which can be actuated to pull the belt to thereby cause movement of the belt at least in a first direction from the first jaw to the second jaw.

Since the belt pulling structure can pull the belt from one jaw to the other jaw, it allows an easy and safe reorientation of the object. Since the object is partly enwrapped by the belt, it moreover, protects the object and potentially allows very precise reorientation.

Since the belt is unsupported, it is not limited in its ability to be pulled in either direction, and the ability to reorient the object is increased.

By "unsupported" is herein meant that the belt is not fixed to mounting points or guiding rollers or other obstacles hindering the free movement of the belt between the leading edges. This allow the object to be completely in contact with the belt in the area between the leading edges and thereby potentially improves the ability of the gripper to rotate the object in the space.

Additional advantages include the ability to reorient at a high speed. Additionally, the gripper is versatile. The gripper can rotate rigid and flexible or odd-shaped objects. Preferred objects for handing are however slightly rounded objects like chicken pieces, e.g., drumsticks, chicken fillets, or parts hereof, chicken tenders, and other food objects.

The gripper may be reliable, and objects can be securely gripped since it is fully enclosed by the belt. Moreover, the gripper and particularly, the gripper footprint can be very compact.

The base may comprise a fixture for fixing the gripper to a manipulator, e.g., a robot, and it may be made from a low weight material such as POM, Nylon, Stainless steel, and/or Titanium.

The jaws may have individual, i.e., different shapes, or they may be identical, or they could be mirrored in a vertical plane centrally between the jaws.

The belt could be a pliable belt, e.g., a sheath of fabric, particularly of a water-resistant material, e.g., a polymer material. The belt could be a homogenous belt, e.g., a hydrolysisresistant belt, e.g., a polyurethane conveyor-type belt or similar type of belt well known in the food industry for conveying meat etc. Particularly, it may be configured to repel oil, grease, moisture, virus, and bacteria etc.

The belt could be elastically stretchable which may provide a closer contact around the object, or alternatively, the belt could be un-stretchable which may improve the ability to precisely control the re-orientation of the object. Particularly, an un-stretchable belt may enable a more direct transfer of the pulling of the belt to the rotation of the object in the gripper.

In one embodiment, the belt could be elastically stretchable transverse to the direction between the leading edges, i.e., transverse to the direction in which the belt moves for reorienting the object. This may provide a closer contact around the object. At the same time, the belt could be un-stretchable in the direction in which the belt moves for reorienting the object which may then improve the ability to precisely control the re-orientation.

The gripper could be made for hygienic or even sterile handling of food objects. For this purpose, all parts could be non-corrosive and suitable for washing or even steam cleaning with hot water or vapour.

For moving the gripper between the closed and the open state, the gripper may include power-driven actuators. For handling food objects, these could be sealed completely and be made to avoid contamination of the handled object, e.g., with oil or other contaminants. The base and jaws could e.g., be made of a non-toxic polymer material of a kind known for food handling, e.g., nylon, vinyl, PPE, POM, or similar polymer material.

In one embodiment, the power-driven actuator is a one-way actuator configured when active to move the gripper from the open to the closed configuration and when inactive not to provide any force on the jaws. In this embodiment, the belt, when tightened about the object may open the jaws, when the power-driven actuator is inactive.

In one embodiment, the power-driven actuator is a two-way actuator configured when active in a first active state to move the gripper from the open to the closed configuration and when active in a second state to move the gripper from the closed configuration to the open configuration. In this embodiment, the object can be released by actively opening the jaws without the use of the belt for this purpose. The actuator of this embodiment may include a third, inactive state, in which it provides no force on the jaws and therefore allows the jaws to be moved to the open or closed state e.g., by the belt.

In addition to the open and closed state, the gripper may define one or more intermediate positions of the jaws, i.e. positions between the open and the closed states. The intermediate positions may e.g. allow opening only to an extend needed for releasing an object from the gripper. This may provide more exact delivery of the object and reduce unnecessary movement of the jaws.

The base could include a fixture for fixing the base to handling equipment, e.g., for attaching the gripper to a robot.

The entire jaw, or at least the leading edge of the jaw could be elastically deformable to allow absorption of tolerances in the handling equipment by allowing deformation of at least the leading edge of the jaw upon contact with the surface where the object is picked up or delivered.

If the belt is disturbed, disrupted or interfered with other objects in the area between the leading edges of the jaws, it may impair the ability to provide a firm grip around the object. The belt may therefore be movable towards a straight configuration where it extends directly from the leading edge of the first jaw to the leading edge of the second jaw in the release procedure. Directly, in this respect, means without being in contact with anything in the area between the leading edges unless an object is gripped. In one embodiment the belt extends straight between the leading edges when no objects are gripped. That reduces the risk of entangling the belt with obstacles during movement of the gripper.

The belt may be movable away from the straight configuration where it extends straight from the leading edge of the first jaw to the leading edge of the second jaw in the gripping procedure. I.e., the object which is gripped may urge the belt away from the straight configuration, such that the object itself pulls a tensioned belt into the space whereby the belt remains stretched at all times.

Alternatively, the gripper could be configured to control the belt such that it is pendant, i.e. hanging loosely like a hammock. The belt could e.g., be suspended freely between opposite sides of the gripper and not touch the jaws prior to the contact with the object, or the belt could follow an outer surface of the jaws but be freely hanging between the leading edge of the first jaw and the leading edge of the second jaw initially in the gripping procedure before the belt touches the object. The pendant belt may facilitate introduction of the object into the space essentially without exerting force against the object, or at least not exerting force of a tensioned belt against the object.

The belt pulling structure may be configured for releasing the belt such that it can be deflected into the space during simultaneous release of the belt when the object is gripped, thereby reducing a need for direct force from the object to the belt in the gripping procedure.

It is generally desired to maintain a certain tension in the belt during the rotation. As will be explained herein, this tension can be obtained either by power-driven actuators or by a spring structure.

In an embodiment, the belt pulling structure is configured for acting actively to maintain the belt in a stretched condition, i.e. maintain tension in the belt while it is configured for releasing the belt into the space in a controlled manner, e.g., based on information related to the object which is gripped. In this embodiment, there is no need for a pressure from the object onto the belt for releasing the belt into the space within the gripper since the belt pulling structure will actively release the belt to maintain the tension.

In another embodiment, the belt pulling structure may be configured for allowing the belt to be released such that it can be deflected into the space upon contact with the object when it is gripped. In this embodiment, the belt pulling structure simply applies a specific tension, and force from the object onto the belt moves the belt into the space, and only exactly enough of belt is deflected into the space. Moreover, this principle may reduce the complexity of the belt control since there is no active release of belt from the belt pulling structure.

The gripper may comprise a control system configured to control the reorientation of the object, particularly to control the belt puling structure. This control system may be configured to read a rotation request indicating a desired reorientation of the object and to control the belt pulling structure to pull the belt in accordance with the desired reorientation.

The desired reorientation may e.g., be keyed in by an operator, or it may be generated automatically, e.g., based on a generally desired orientation for a specific object. If the object is a food object, such objects may have a front and a back surface, or opposite side surfaces etc., and the desired orientation may be with the front surface upwards etc. Accordingly, the gripper may comprise an automatic recognition system capable of determining an orientation and compare that orientation with a desired orientation, to provide therefrom a desired reorientation of the object, and to feed the desired reorientation to the control system which in response controls the belt pulling structure.

The gripper may comprise a belt displacement sensor configured to provide a belt displacement signal representing a length of the belt being pulled into the space. The belt displacement sensor may form an integrated part of the belt pulling structure, e.g., as an integrated part of an electrical motor arranged to pull the belt, or the sensor could be an external component, e.g. a spring-loaded sensor pressing against a surface of the belt and having displacement sensing capability, e.g. based on a moving roll, light reflection, or other means.

The control system may be configured to read a desired rotation, e.g. being the above mentioned desired reorientation, to predict a cross-sectional size or shape of the object based on the belt displacement signal, to determine a ratio between a belt pulling length and a corresponding angle of rotation of the object, and to control rotation by use of the belt pulling structure based on the desired rotation and the ratio. This will allow automatic reorientation.

The gripper may comprise a belt tension sensor configured to provide a belt tension signal representing a tension of the belt during the gripping procedure, wherein the control system is configured to control the belt pulling structure based on the belt tension signal for releasing the belt such that it can be deflected into the space based on a pre-specified tension. This may provide the effect that no, or only very little force from the object is required onto the belt when the object is gripped. The belt pulling structure comprises a first actuation unit and a second actuation unit. The two actuation units may be arranged to pull the belt in opposite directions across the gap. They may e.g. be located on opposite sides of a vertical plane extending between the jaws through the gap.

In one embodiment, at least one of the first and second actuation units may comprise at least one power-driven actuator. The power-driven actuator could e.g., be a pneumatic or an electric linear actuator, a pneumatic or electric rotational motor, e.g., a stepper motor, or a controllable motor in general.

In one embodiment, at least one of the first and second actuation units comprises at least one passive spring structure. The passive spring structure could e.g., comprise a linear or rotational spring, or an air influenced actuator etc.

If there is only one power-driven actuator, then this actuator may pull the belt in one direction relative to the gap and the passive spring structure may be arranged to maintain the tension in the belt. The spring structure may work in different ways depending on the layout of the belt.

In a first embodiment, the belt is an endless belt, and the at least one power driven actuator is arranged for rotating the endless belt. In this embodiment, the spring structure may act like a belt tensioner known inter alia from transport belts, timing belts and similar structures operating with endless belts.

In a second embodiment, the belt is not an endless belt but, on the contrary, extends between opposite free ends. In this embodiment, a power-driven actuator may act to pull one of the free ends in one direction while the spring structure, or another power-driven actuator may act to pull the other free end against this direction and thereby maintain tension in the belt.

The belt pulling structure could be actuated for pulling in a selective direction to thereby cause selective movement of the belt in the first direction from the first jaw to the second jaw, or in a second direction from the second jaw to the first jaw.

In operation, the belt may be actively pulled from one jaw towards the opposite jaw by actively pulling the belt at one of the first and second actuation units. This would typically be a power-driven actuation unit. During this movement, the other actuation unit may either actively release the belt, or the belt may be released against a certain counter hold force provided by the other actuation unit. This counter hold force could be generated by the accumulation of feree in a spring structure of that actuation unit. It could also be achieved by one actuation unit applying a constant torque by power-driven actuation.

The belt may have an inner surface and an opposite outer surface, the outer surface sliding in direct contact with the leading edges of the first jaw and the second jaw and having a lower or equal surface friction than the inner surface. This may reduce friction against sliding on the jaw while maintaining a good grip in the object which is gripped.

At least one leading edge of the first and second jaw may include a rotationally suspended pulley on which the belt moves while the pulley rotates. This may further reduce the friction against sliding between the jaw and the belt, it may reduce wear on the belt, and it may reduce the needed force from the power-driven actuation unit and thus reduce the size and weight of the gripper.

A data-input may be provided for reading an object orientation signal from a sensor, and the system could be configured to allow the belt pulling structure to pull the belt based on the object orientation signal. As an example, cameras or other sensors could be used for generating a signal representing the orientation of the object before it is picked up. The signal may e.g., indicate, upside down, or sideways, etc. This orientation signal is read by the gripper by the data-input and utilised by the belt pulling structure to define a specific reorientation, e.g., turning the sideways orientation into upside down, etc.

The gripper may comprise a sensor configured for providing the object orientation signal indicative of an orientation of the object. The gripper may e.g., include a mechanical or optical sensor, e.g., a camera, which can determine the orientation of the object in the space, i.e., after it is gripped. Based on this signal, the belt pulling structure may reorient the object to obtain a desired orientation. The advantage of including the sensor in the gripper is that the actual orientation in the gripper may be determined which could be more precise than determining an orientation before the object is gripped.

At least one of the first jaw and the second jaw could be pivotally mounted on the base, and/or at least one of the first jaw and the second jaw could be mounted for a translatory sliding movement relative to the base.

The first jaw and the second jaw may each comprise an object compressing section between the base and the leading edge. The object compressing section(s) is defined as a part of the jaw which meets the object and compresses the object when the object is gripped. This section may particularly extend at an angle above 60 degrees to each other, such as above 90 degrees to each other, however mainly below 170 or below 150 degrees to each other. Particularly, when the object does not have a circular cross-section, the angle may be important relative to the ability to reorient the object. As an example, it may be easier to reorient an object with an oval cross section if the angle is above 60 degrees.

The angle between the object compressing sections may vary along the jaw, particularly such that the angle becomes smaller and smaller in the upwards direction from the leading edges towards the base.

The object compressing sections could be symmetrically about the previously mentioned virtual, vertical, centre plane extending between the jaws.

In a second aspect, the disclosure herein includes a robot system carrying the gripper according to the first aspect. The robot system may particularly comprise a Delta robot.

In a third aspect, the disclosure provides a method of orienting an object by use of a gripper according to the first aspect.

The method comprises: moving the gripper in the open state to a first position toward the object until the object is in the space and thereby deflecting the belt into the space, arranging the gripper in the closed state while the object is in the space to thereby grip the object in the space, actuating the belt pulling structure to thereby rotate the object while the object is in the space, and arranging the gripper in the open state to release the object from the space,

The method may e.g., be applied for food objects, particularly oval objects, flexible objects, and/or elongated objects.

Optionally, the tension may be applied in the belt before and while the rotation of the object in the gripper takes place.

The method may further comprise moving the gripper to a second position before arranging the gripper in the open state. The method may further comprise arranging a packaging at the second position and releasing the object from the space directly to the packaging.

The release of the object could be facilitated by belt, particularly by stretching the belt while opening the jaws.

The method may comprise the step of characterising a cross-sectional size or shape of the object and determining based on the characterising, a ratio between a belt pulling length and a corresponding degree of rotation of the object.

The characterising of the object may comprise the step of reading a movement of the belt when the object enters the space. This movement could be determined by reading an electrical signal from a power-driven actuation unit. The actuation unit may e.g., comprise a stepper motor, and by reading the stepper signal from the stepper motor, the distance of the belt which was deflected into the space when the object was gripped, can be determined.

When knowing the length increase of the belt necessary to capture the object, the size of the object can be estimated, and the ratio between a specific pull in the belt and a resulting degree of rotation of the object in the gripper can be determined.

LEGENDS TO THE FIGURE

Fig. 1 illustrates a gripper in the open state;

Fig. 2 illustrates a gripper in the closed state;

Fig. 3 illustrates a perspective view of the gripper;

Fig. 4 illustrates sensing of orientation for the purpose of reorienting the object;

Fig. 5 illustrates sensing of orientation of the object while it is in the space in the gripper;

Fig. 6 illustrates specific angles of the object compressing section of the jaws;

Fig. 7 illustrates a Delta robot with a gripper;

Fig. 8 illustrates inner and outer surfaces of the belt; Fig. 9 illustrates a jaw with a rotating pulley reducing friction against belt movement;

Fig. 10 illustrates a passive spring forming an actuation unit;

Figs 11-13 illustrate aspects of different angles of compressing sections of the jaws;

Figs. 14 and 15 illustrate details of receipt of an object in the space.

Fig. 16 illustrates a gripper and two axes of rotation illustrated by arrows;

Fig. 17 illustrates an embodiment where the belt 9 is an endless belt,

Figs. 18-20 illustrate different method steps of moving and/or reorienting an object, and

Figs. 21-22 illustrate embodiments where the belt is controlled to hang freely before contact with the object.

DETAILED DISCLOSURE OF THE INVENTION

Definitions

The term "object compressing section" refers to a part of the jaw potentially abutting the object directly through the belt during the process of reorienting the object.

The term "un-stretchable belt" refers to a belt which is essentially not elongated by the forces applied to the belt during use. The stretchability may be less than 1 pct relative to the unstretched length.

The term "rotation in the gripper" refers to the rotation of the object with respect to the gripper, i.e. the rotation of the object in the space caused by the function of the gripper when pulling the belt. On the contrary, rotation of the gripper is a rotation which rotates both the gripper and thereby also the object. This rotation could be caused by a robot.

The term "tension" refers to a pulling force and "belt tension" is therefore the pulling force in the belt. Specific embodiments of the invention

Fig. 1 illustrates a gripper 1 for gripping an object 2 from a surface 3. In Fig. 1, the gripper is in the open state and ready to grip, and in Fig. 2, the gripper is in the closed state.

The gripper 1 comprises a base 4 which is attachable to a manipulator such as a robot. A first jaw 5 and a second jaw 6 are both mounted pivotally to the base for rotation about the pivot structures 7, 8. The gripper further comprises a belt 9 extending from one of the first jaw and the second jaw across a gap 10 between the leading edges 11, 12 of the first jaw and the second jaw.

The belt extends, unobstructed and directly from one leading edge to the other leading edge therefore enabling complete encapsulation of an object which is gripped.

The gripper can grip the object 2 which is on the surface 3 by moving the first and second jaws 5, 6 to the closed position on opposite sides of the food object, such that the object is held in the space 14 above the leading edges 11, 12 of the jaws.

The belt is controlled by a belt pulling structure arranged to interact with the belt 9 and releasably stretches the belt such that moderate tension can be maintained while the belt is deflected into the space above the leading edges.

The belt pulling structure may include at least a first actuation unit 15 and a second actuation unit 16. In this case constituted by a first power-driven actuator and a second power-driven actuator arranged to drive belt pulleys. The power-driven actuators could be constituted by stepper motors or similar servo motors.

Additionally, the belt control structure comprises a control system, e.g., implemented in a standard computer control structure. The control system is arranged to control belt actuation units, e.g., via pulley(s), to maintain the tension while allowing the release of the belt into the space 14. The computer control is not illustrated in Figs. 1 and 2 but it could e.g., be integrated in one of the first and second actuation units 15, 16 or both in the first and second actuation units 15, 16.

The first and second actuation units are on opposite sides of a vertical plane extending between the first jaw and second jaw, i.e., on opposite sides of the centre plane 20. The belt pulling structure can be actuated to pull the belt as indicated by the arrow 17. The pulling causes movement of the belt in a first direction indicated by the arrow 18 from the first jaw to the second jaw. This will cause rotation of the object in the gripper as indicated by the arrow 21.

The gripping actuator 19 includes a pneumatic cylinder, or other power-driven means for moving one or both first jaw and the second jaw between the open and the closed position. In one embodiment, the gripping actuation structure 19 comprises a spring structure biasing the first jaw and the second jaw towards the open position and power-driven means for operation against the force of the spring structure towards the closed position.

Fig. 1 illustrates the releasably stretched conditions of the belt such that tension can be maintained while the belt is deflected into the space upon contact with the object 2 when it is gripped. Fig. 2 illustrates that the belt becomes curled around the object 2 such that the object can be rotated by pulling the belt. The illustrated object could be a chicken breast fillet or chicken drum stick etc., which becomes deformed by the belt which encircles it in the space. This is particularly suitable for establish a firm grip and easy reorienting of the object.

The first and second jaws are symmetric about the centre plane 20 and they both open symmetrically relative to the centre plane 20.

Fig. 3 illustrates a perspective view of the gripper 1. The first actuation unit 15 and the second actuation unit 16 can more easily be seen. Particularly, it is clearly seen that each actuation unit comprises a power-driven actuator 30, 31 and a corresponding belt pulley 32, 33 driven by the respective one of the power-driven actuators. The CPU 34 illustrates a control system for controlling the two actuators.

In operation, the control system 34 receives torque information from the power-driven actuators 30, 31 via the communication channels 35, 36 and dispatches control commands to the power-driven actuators. The control can be split into four control phases indicated as phase a, b, c, and d.

Control phase a) is a passive control phase where the gripper is ready to receive an object. In this phase, the control system 34 maintains a basic tension in the belt, and the power- driven actuators apply just enough torque to maintain this basic tension.

Control phase b) is a first active control phase where the gripper receives an object in the space. During this procedure, the belt is un-winded by one or both actuation units while the basic tension is at least essentially being preserved. During this procedure, the control system 34 continuously or with a high clock frequency, receives torque information from each of the power-driven actuator 30, 31. In response to the torque, the control system returns commands to unwind based on the desire to maintain the torque.

Control phase c) is a second active control phase. This control phase is triggered by the jaws being fully closed, i.e., the gripper is in the closed state. In control phase c), the control system 34 commands one or both power-driven actuators 30, 31 wind up and increase the torque until a desired, pre-orientation torque is reaches. The control system 34 may simultaneously receive torque information from each of the power-driven actuators 30, 31, or the control system may be pre-programmed to simply wind a certain length of the belt, or a certain duration. The latter is particularly relevant when the handled objects are nearly identical, whereas large differences between the handled objects may necessitate the torque feedback.

Control phase d) is a third active control phase in which the gripper reorients the object which is in the space. In control phase d), the control system 34 commands one of the power-driven actuators 30 to wind up and the other power-driven actuator 31 to un-wind while the torque is essentially maintained at the pre-orientation torque. The control system 34 may simultaneously receive orientation information from a sensor, or the control system may be pre-programmed to simply wind and un-wind a certain length of the belt, or a certain duration. The latter is particularly relevant when the handled objects are nearly identical, whereas large differences between the handled objects may necessitate the sensor feedback.

The control system 34 depicted in Fig. 3 comprises a data-input 37 configured to read an object orientation signal from a sensor, e.g., a camera-based vision system 38. The control system controls the belt pulling structure such that it becomes configured for pulling the belt from one of the first jaw and the second jaw towards the other one of the first jaw and the second jaw based on the object orientation signal from the sensor.

Fig. 4 illustrates use of the sensor for obtaining an actual orientation indicated by the solid line 40 illustrating the actual orientation of an object 2. The control system 34 comprises information about a desired orientation of the food object, illustrated by the dotted line 41. The control system 34 is configured to calculate necessary rotation of the food object, indicated by the arrow 42, and to control the pulling structure accordingly for obtaining the desired orientation.

The sensor could be located anywhere near the place where the gripper is to grip the object. Fig. 5 illustrates a sensor which is arranged to provide the object orientation signal indicative of the orientation while the object is in the space in the gripper. In this embodiment, the gripper may grip a object in an arbitrary orientation and once the object is fixed in the space, the orientation is determined. This reduces the risk of unexpected reorientation of the object in the time frame between the orientation of the object is recognized by the sensor and the time where it is fixed in the gripper.

In the embodiments of Figs. 1-5, the first jaw 5 and the second jaw 6 are both mounted pivotally to the base for rotation about the pivot structures 7, 8 which are offset relative to each other. However, at least one of the first jaw and the second jaw could alternatively be mounted for a translatory sliding movement relative to the base on a linear guide structure.

Fig. 6 illustrates the first jaw and the second jaw each comprises an object compressing section 60 and a leg section 61. The object compressing section 60 is between the leg section 61 and the leading edge 11, 12. The leg section is between the base 4 and the compressing section. In use, the object is compressed between the compressing sections of the two jaws.

In Fig. 6, the object compressing sections extend at an angle of 100 degrees to each other, i.e., the angle, 62 is 50 degrees. In general, it is desired that the angle 62 is above 30 degrees, e.g., above 45 degrees, thereby making the angle between the object compressing sections at least 60 degrees, such as 90 degrees to each other. As illustrated in Fig. 6, the object compressing sections are preferably symmetrically about a centre plane illustrated by the dotted line 63.

Fig. 7 illustrates a Delta robot system for handling food objects. This robot carries a gripper as disclosed herein and it is used inter alia for handling food objects such as fish portions, chicken breast, chicken drumsticks and similar food objects.

In use, the robot moves the gripper in the open state to a first position in which the object becomes located in the space. During this movement, the belt is deflected into the space by the force of the gripper being pushed down over the object.

When the object is in the space, the gripper is moved to the closed state and thereby grips the object.

The belt pulling structure is actuated to thereby rotate the object while the object is in the space, and the gripper is moved to the open state to release the object from the space in the newly obtained orientation. The reorientation of the object may occur while the gripper is moved to a second position whereby the duration of the movement of the object is utilized for the reorientation of the object.

The gripper may be used efficiently, e.g., for packaging food objects in trays or boxes, and the ability to reorient the food object can be utilized for arranging the food object in a manner where they require less space, or where the food object has a more appealing appearance.

Fig. 8 illustrates an inner surface 80 of the belt. The inner surface faces the object which is gripped and has a relatively high surface friction obtained by used of surface structures 81. This high surface friction reduces slipping between the belt and the object and increases the ability to rotate the object. Fig. 8 also illustrates an outer surface 82, i.e., opposite the inner surface. The outer surface slides in direct contact with the leading edges of the first jaw and the second jaw, and to reduce friction, it has no surface structures and therefore a lower surface friction than the inner surface.

Fig. 9 illustrates a jaw, and illustrates at the leading edge, a rotationally suspended pulley 90 on which the belt moves while the pulley rotates. This rotational pulley reduces friction between the leading edge and the belt. As an alternative to the rotational pulley at the leading edge, the leading edge may have a smoothly rounded shape and optionally be made of a low frictional material such as Teflon, nylon, or similar plastic material.

Fig. 10 illustrates an embodiment where the belt pulling structure comprises a power-driven actuator forming the first actuation unit 15 arranged in one side of the gripper for pulling the belt in the first direction, and a passive spring structure 100 forming the second actuation unit and arranged to counteract the actuator by pulling the belt in the second direction.

Figs. 11 and 12 illustrate two different versions of the gripper with different compressing sections. In Fig. 11, the angle between the object compressing sections is smaller than in Fig. 12. More particularly, the angle in Fig. 11 is lower than 90 degrees between the compressing sections of the jaws, and in Fig. 12, the angle is above 90 degrees between the compressing sections.

The grip angle is herein defined as an angle between the object compressing section and vertical, and it is, in a symmetric layout of the jaws, 50 pct. of the angle between the object compressing sections of the jaws. Fig. 13 illustrates in a diagram how the tension is reduced when the grip angle increases. The diagram is a result of experiments with a specific object, namely a chicken drumstick. In Fig. 13, the vertical axis illustrates the belt tension in percentage, and the horizontal axis illustrates the grip angle in degrees. The diagram includes several different measures of the dimension illustrated as dimension b in Fig. 11 and with a fixed measure of the dimension a. In the specific example, a is 30 mm and b varies in steps of 1 mm. from 20 mm to 29 mm where 20 mm is the top graph and 29 mm is the bottom graph.

As illustrated by the diagram, the angle of the object compressing sections influences the tension and ability of the gripper to reorient the object. Accordingly, Fig. 13 illustrates that by increasing the angle, the belt tension needed to reorient the object may be reduced.

Figs. 14 and 15 illustrate details of receipt of an object in the space 14. In Fig. 14, the gripper is pushed downwards over the object 2 which is located on the surface 3, e.g., a surface of a conveyor belt of a food processing system. In this embodiment, the first actuation unit 15 actively releases the belt such that a constant tension is maintained while the object and thus the belt moves into the space during the gripping procedure. As an alternative to the active release of the belt from the first actuation unit 15, the belt pulling structure may release the belt, e.g., such that it is tensioned by a spring force, and allowed to be pulled from the first actuation unit 15. I.e., the object pulls the belt out when it enters the space.

Fig. 15 illustrates schematically that the degree of rotation, indicated by the arrow 141 is measured. The degree of rotation indicates the length of the belt which is pulled into the space and thus indicates the size of the object which is gripped. Herein, we refer to this belt length as the length being absorbed during gripping. As will be explained below, this length may be used for predicting the pull length which is required for obtaining a specific reorientation of the object.

If the absorbed length is known, it can be converted into a ratio between a belt pull and a corresponding reorientation of the object.

In one example, the absorbed length is 20 centimetres. This indicates the length of the circumference or the size of the cross-section of the object which is picked up. In the following example, it is for simplicity considered to be an object having a circular cross- sectional shape, and similar examples may be made for other shapes.

For a circle, the circumference, C=2*pi*r. Accordingly, r=C/(2*pi) Accordingly, if C is nearly 20 centimetres which where the amount of belt being pulled into the space during the gripping, then the approximated radius of the product r=20/6,28=3,2 centimetre.

If it is desired to reorient the object by a 20 degrees rotation, we need to pull a distance corresponding to (20/360)*2*pi*3,2 centimetres = 2,2 centimetres.

Considering that the object may not be perfectly circular, the above procedure may only provide an approximal pulling length providing a specific reorientation. However, by reorienting a large amount of similar food products in practise, e.g. chicken breasts, a table of absorbed length and a corresponding ratio of pulling length for a specific reorientation may be determined with a fair accuracy.

Fig. 16 illustrates a gripper and two axes of rotation illustrated by arrows 160 and 161. The axis of rotation illustrated by arrow 160 is a rotation which rotates both the gripper and thereby also the object. This rotation could be caused by a robot attached to the robot attachment flange 162. The other axis of rotation illustrated by the arrow 161 illustrates rotation in the gripper, and thereby refers to the rotation of the object with respect to the gripper, i.e. the rotation caused by the function of the gripper.

Fig. 17 illustrates an embodiment where the belt 9 is an endless belt. In this embodiment, the first actuation unit 15 could be a power-driven actuator configured to rotate the endless belt in the direction indicated by the arrow 17. The second actuation unit 16 could be a passive spring structure with a belt pulley. The spring structure is arranged to apply tension to the belt as indicated by the arrow 170. The belt pully could be a passive pulley simply rotated by the rotation of the belt, or it could even be a low friction surface with no rotation, on which the belt slides when rotated by the first actuation unit 15. Alternatively, both the first and second actuation units could be power driven and move the belt actively while the spring structure maintains the tension.

Fig. 18 illustrates a method of reorienting an object. According to this method, step A is a step in which the gripper is moved to a first position toward the object. The gripper is in an open state, or the gripper is changed to an open state, and the gripper is placed in a position where the object is in the space. This deflects the belt into the space.

In step B, the gripper is changed to the closed state while the object is in the space. Accordingly, the object is gripped and held in the space. In step C, the belt pulling structure is actuated to thereby rotate the object while the object is in the space.

In step D, the object is delivered by arranging the gripper in the open state. This releases the object from the space in the orientation achieved by the rotation in step C.

Fig. 19 illustrates an expanded version of step D, in which step D is divided into two substeps DI and D2. DI is a step of moving the gripper to a second position before arranging the gripper in the open state, and D2 is the step of opening the gripper.

Fig. 20 illustrates an expanded version of step C, in which step C is divided into two substeps Cl and C2. Cl is a step of requesting if the orientation of the object matches a desired orientation. In case of YES, the process directly continues with step D, e.g. divided into DI and D2. In case of NO, the process continues in step C2 to actuate the belt pulling structure and rotate the object while the object is in the space until the correct orientation is achieved.

Fig. 21 illustrates an embodiment corresponding to the embodiment of Fig. 1, however, in which the belt is hanging loosely in the area where the object is approached by the belt, herein this is referred to as the belt being pendant. This allows the object 2 to be more freely entering the space 14 only having to lift the belt but not having to work against a belt tension. In this embodiment, the belt pulling structure may be configured to release the belt while the object enters the space 14 to thereby avoid belt tension before the object is received. In the specific embodiment, the belt is pendant between the leading edge of the first jaw and the leading edge of the second jaw but follows an outer surface of the jaws. This may reduce the risk of entangling the belt with obstacles during movement of the gripper, and it could be obtained by suitable design of the grippers, location of the actuation units 15, 16, and/or by passing the belt through guides, e.g., rollers, at the leading edges.

Fig. 22 illustrates an embodiment corresponding to the embodiment of Fig. 21, however, in which the belt initially in the gripping procedure is pendant between the first and second actuation units 15, 16 as opposed to the leading edges. This provides better movability for the belt.

Claims

1. A gripper (1) for gripping an object (2) in a gripping procedure and for releasing the object in a release procedure, the gripper (1) comprising : a base (4), a first jaw (5) mounted on the base, a second jaw (6) mounted on the base, and a belt (9), wherein each jaw defines a leading edge (11, 12) and at least one of the first jaw and the second jaw is movable relative to the base and relative to the other jaw to arrange the gripper in an open state or a closed state, wherein the leading edges (11, 12) are closer to each other in the closed state than in the open state to thereby allow receiving and holding an object in a space (14) defined by the jaws, and wherein the belt (9) extends between the leading edges, the gripper further comprising a belt pulling structure which can be actuated to pull the belt to thereby cause movement of the belt in a first direction from the first jaw to the second jaw, wherein the belt (9) is unsupported between the leading edge of the first jaw and the leading edge of the second jaw.

2. The gripper according to claim 1 wherein the belt (9) is movable towards a straight configuration where it extends directly from the leading edge of the first jaw to the leading edge of the second jaw in the release procedure.

3. The gripper according to any of the preceding claims, wherein the belt (9) is movable away from a straight configuration where it extends straight from the leading edge of the first jaw to the leading edge of the second jaw in the gripping procedure.

4. The gripper according to any of claims 1 or 2, wherein the belt is pendant initially in the gripping procedure.

5. The gripper according to any of the preceding claims, wherein the belt pulling structure is configured for releasing the belt such that it can be deflected into the space during simultaneous release of the belt when the object is gripped, thereby reducing a need for direct force from the object to the belt in the gripping procedure.

6. The gripper according to any of claims 1-4, wherein the belt pulling structure is configured for maintaining the belt in a releasably stretched condition while it is released into the space upon contact with the object in the gripping procedure.

7. The gripper according to any of the preceding claims, comprising a control system configured to read a rotation request indicating a desired reorientation of the object and to control the belt pulling structure to pull the belt in accordance with the desired reorientation.

8. The gripper according to claim 7, comprising a belt displacement sensor configured to provide a belt displacement signal representing a length of the belt being pulled into the space (14) during the gripping procedure, wherein the control system is configured to read a desired rotation, to predict a cross-sectional size or shape of the object based on the belt displacement signal, to determine a ratio between a belt pulling length and a corresponding angle of rotation of the object, and to control rotation by use of the belt pulling structure based on the desired rotation and the ratio.

9. The gripper according to claims 7 or 8, comprising a belt tension sensor configured to provide a belt tension signal representing a tension of the belt during the gripping procedure, wherein the control system is configured to control the belt pulling structure based on the belt tension signal for releasing the belt such that it can be deflected into the space based on a pre-specified tension.

10. The gripper according to claim 9, wherein the control system is configured to control the belt pulling structure based on the belt tension signal to maintain the belt in a releasably stretched conditions while it is released into the space upon contact with the object in the gripping procedure.

11. The gripper according to any of the preceding claims, wherein the belt pulling structure comprises a first actuation unit (15) and a second actuation unit (16).

12. The gripper according to claim 11, wherein the first and second actuation units are on opposite sides of a vertical plane between the first jaw and second jaw.

13. The gripper according to any of claims 11 or 12, wherein at least one of the first and second actuation units comprises at least one power-driven actuator.

14. The gripper according to claim 13, wherein at least one of the first and second actuation units comprises at least one passive spring structure arranged to provide tension or pull in the belt.

15. The gripper according to any of the preceding claims, wherein the belt pulling structure can be actuated for pulling in a selective direction to thereby cause selective movement of the belt in the first direction from the first jaw to the second jaw, or in a second direction from the second jaw to the first jaw.

16. The gripper according to any of the preceding claims, wherein the belt has an inner surface and an opposite outer surface, the outer surface sliding in direct contact with the leading edges of the first jaw and the second jaw and having a lower or equal surface friction than the inner surface.

17. The gripper according to any of the preceding claims, wherein at least on leading edge of the first and second jaw includes a rotationally suspended pulley on which the belt moves while the pulley rotates.

18. The gripper according to any of the preceding claims, comprising a data-input configured to read an object orientation signal from a sensor and wherein the belt pulling structure is configured for pulling the belt based on the object orientation signal

19. The gripper according to claim 18, comprising a sensor configured for providing the object orientation signal indicative of an orientation of the object.

20. The gripper according to claim 19, wherein the sensor is arranged to provide the object orientation signal indicative of the orientation while the object is in the space.

21. The gripper according to any of the preceding claims, wherein at least one of the first jaw and the second jaw is pivotally mounted on the base.

22. The gripper according to any of the preceding claims, wherein at least one of the first jaw and the second jaw is mounted for a translatory sliding movement relative to the base.

23. The gripper according to any of the preceding claims, wherein the first jaw and the second jaw each comprises an object compressing section between the base and the leading edge, the object compressing sections extending at an angle above 60 degrees to each other.

24. The gripper according to claim 23, wherein the object compressing section is a curved section.

25. The gripper according to claim 23 or 24, wherein the object compressing sections are symmetrically arranged about a centre plane.

26. A robot system for handling food objects, the robot system carrying the gripper according to any of the preceding claims.

27. A robot system according to claim 26, wherein the robot system comprises a Delta robot.

28. A method of orienting an object by use of a gripper according to any of the preceding claims, the method comprising : moving the gripper in the open state to a first position toward the object until the object is in the space and thereby deflecting the belt into the space, arranging the gripper in the closed state while the object is in the space to thereby grip the object in the space, actuating the belt pulling structure to thereby rotate the object while the object is in the space, and arranging the gripper in the open state to release the object from the space.

29. The method according to claim 28, comprising moving the gripper to a second position before arranging the gripper in the open state.

30. The method according to any of claims 28-29, comprising arranging a packaging at the second position and releasing the object from the space directly to the packaging.

31. The method according to claim 28-30 comprising releasing the object from the space directly to a processing station and processing the object in an orientation obtained by rotation of the object in the gripper.

32. The method according to any of claims 28-31 comprising a step of characterising a cross-sectional size or shape of the object and determining based on the characterising a ratio between a belt pulling length and a corresponding degree of rotation of the object.

33. The method according to claim 32, wherein the characterising of the object comprises reading a movement of the belt when the object enters the space.

34. The method according to claim 33, wherein the reading of the movement comprises reading an electrical signal from one of the first and second actuation units.

35. The method according to any of claims 28-34, wherein the gripper is moved towards the closed state by power-driven means when the object has entered the space.

36. The method according to claim 35, wherein the gripper is moved towards the open state by actuation of the belt.