FIELD OF THE INVENTION

[ 01 ] The invention relates to an end-effector for a delta robot comprising three actuated robot arms for coupling to the end-effector to allow moving the end-effector by the robot arms. The end-effector comprises a housing having a vacuum connection for connecting to an external vacuum source, and having a main duct in fluid communication with the vacuum connection; and a hollow shaft mounted in the housing to be rotatable around a longitudinal axis of the hollow shaft, wherein the hollow shaft has a hollow interior, a proximal shaft opening at a proximal end of the hollow shaft inside the housing to provide fluid communication between the hollow interior and the main duct, the hollow interior extends along the longitudinal axis of the hollow shaft to a distal end of the hollow shaft, and the distal end projects from the housing, the distal end allowing for connecting a further device thereto and to pass vacuum from the interior of the hollow shaft and rotation by the hollow shaft to the further device, such as a pick-op device for picking up an object by vacuum suction. The invention further relates to a delta robot having such end-effector.

BACKGROUND OF THE INVENTION

[ 02 ] Delta robots are widely used for displacing objects from one location to another or for repositioning objects. An object is picked up by a pickup device provided at the distal end of the hollow shaft of the end-effector of the delta robot through vacuum suction by vacuum passed from the vacuum source, such as a vacuum pump, by the end-effector to the pickup device. The vacuum can be switched on and off for picking up and releasing the object by the pickup device mounted on the hollow shaft of the end-effector. The object can be reoriented by rotation of the hollow shaft. The arms of the delta robot which are coupled to the end-effector allow moving around the end-effector, and thus the object held by the pickup device, in three translation degrees of freedom.

[ 03 ] Each robot arm has an upper arm segment and a lower arm segment that are coupled by a hinge joint allowing for one degree of freedom rotational movement. The upper arm is generally actuated to provide rotational movement in a vertical plane. The lower arm has two parallel rods coupled to the end-effector. Delta robots are extensively employed for moving products, for instance, for taking one or more products from a product supply conveyor into a packing box or for taking one or more products form a product supply conveyor to an intermediate device for further (packing) operations.

[ 04 ] However, present day delta robots have some limitations, especially with respect to the speed at which they can operate and the reach of the end-effector. Rotation of the hollow shaft of the end-effector is achieved by a servo motor together with a reductor mounted on top of the housing. The known constructions add quite a considerable mass to the end-effector and cause the end-effector to extend in the upward direction, both of which are speed limiting for movements of the end-effector. The extension in the upward direction causes reach limitations as well since the upper extension may come into conflict with the robot arms. In alternative designs, a driving shaft is coupled between the end-effector and the central platform on which the robot arms are mounted and actuated from. Rotation of driving shaft by an actuator on the central platform is passed by the driving shaft to the hollow shaft in the end-effector. Such a driving shaft configuration provides speed and reach limitations as well to the delta robot.

[ 05 ] Switching of the vacuum to the hollow shaft requires venting and evacuating rather large volumes in present designs, which drastically reduces the speed at which an object can be picked up and released again. Applications in which delta robots are employed could be improved by an enhancement of the speed and the reach at which delta robots are operated.

SUMMARY OF THE INVENTION

[ 06 ] It is an objective of the invention to provide an end-effector that allows a delta robot to be operated at higher speeds.

[ 07 ] It is another or alternative objective of the invention to provide an end-effector having a reduced mass.

[ 08 ] It is yet another or alternative objective of the invention to provide an end- effector providing an even mass distribution to allow a balanced movement.

[ 09 ] It is yet another or alternative objective of the invention to provide an end- effector providing enhanced reach of the delta robot.

[ 10 ] It is yet another or alternative objective of the invention to provide an end- effector that allows a fast switching on and releasing of the vacuum to the hollow shaft.

[ 11 ] It is yet another or alternative objective of the invention to provide an end- effector having a small volume that requires venting and evacuating for releasing and switching on the vacuum in the hollow shaft.

[ 12 ] At least one of the above objectives is achieved by an end-effector for a delta robot comprising actuated robot arms for coupling to the end-effector to allow moving the end-effector by the robot arms, the end-effector comprising

- a housing having a vacuum connection for connecting to an external vacuum source, and having a main duct in fluid communication with the vacuum connection;

- a hollow shaft mounted in the housing to be rotatable around a longitudinal axis of the hollow shaft, wherein the hollow shaft has a hollow interior, a proximal shaft opening at a proximal end of the hollow shaft inside the housing to provide fluid communication between the hollow interior and the main duct, the hollow interior extends along the longitudinal axis of the hollow shaft to a distal end of the hollow shaft, and the distal end of the hollow shaft projects from the housing, the distal end allowing for connecting a further device thereto and to pass vacuum from the interior of the hollow shaft and rotation by the hollow shaft to the further device, such as a pick-op device for picking up an object by vacuum suction;

- a vacuum valve arranged in the main duct of the housing between the proximal shaft opening and the vacuum connection, wherein the vacuum valve provides for an open position to provide fluid communication between the proximal shaft opening and the vacuum connection to allow providing a vacuum in the hollow shaft when the vacuum connection is connected to a vacuum source and the vacuum valve provides for a closed position to close fluid communication between the proximal shaft opening and the vacuum connection; and - a motor attached to the housing for rotating the hollow shaft around its longitudinal axis with respect to the housing, wherein the motor is arranged in the housing around the longitudinal axis of the hollow shaft, the proximal shaft opening is transverse to the longitudinal axis of the hollow shaft and provides fluid connection between the interior of the hollow shaft and a main duct end section of the main duct, which main duct end section is adjacent to the proximal shaft opening and extends along the longitudinal axis of the hollow shaft, and the vacuum valve in the closed position closes on or in the main duct end section. The end-effector can be made very compact with effectively only the volume of the interior of hollow shaft to be evacuated and vented for passing or releasing vacuum in the further device arranged at the distal end of the hollow shaft.

[ 13 ] In an embodiment the motor is an electrical motor having a rotor and a stator, the rotor being attached to the hollow shaft and the stator being attached to the housing.

[ 14 ] In an embodiment the electrical motor is a brushless torque motor allowing for a position readout of the rotor through the electrical currents and voltages for driving the motor, optionally by at least one of superposing an alternating voltage and measuring self- induction of motor coils of the motor, and measuring counter-electromotive force of motor coils of the motor, which allows determining the position of the motor and therefore of the rotational position of the hollow shaft without a separate position sensor to save on mass and volume of the end-effector.

[ 15 ] In an embodiment the vacuum valve in the closed position is arranged in proximity to the proximal shaft opening, which provides for a minimum volume to be vented and evacuated when operating the further device by vacuum switching.

[ 16 ] In an embodiment the vacuum valve is arranged transverse to the longitudinal axis of the hollow shaft and is movable along a direction of the longitudinal axis of the hollow shaft towards the hollow shaft for the closed position of the vacuum valve, which is an advantageous configuration to provide for a minimum volume to be vented and evacuated when operating the further device by vacuum switching.

[ 17 ] In an embodiment a ridge is provided in or delimits the main channel end section, and the vacuum valve closes against the ridge.

[ 18 ] In an embodiment the main duct end section connects to a main duct transverse section of the main duct which is transverse to the main duct end section, and the vacuum valve closes in the main duct transverse section.

[ 19 ] In an embodiment a seal is provided between a wall of the main duct in the housing and an outer circumference of the proximal end of the hollow shaft. [ 20 ] In an embodiment the seal comprises a PS seal arranged on the wall of the main duct, and a lip of the PS seal seals against the outer circumference of the proximal end of the hollow shaft.

[ 21 ] In an embodiment a vent conduit is provided in the housing in fluid communication with a vent opening into the main duct end section between the vacuum valve in the closed position thereof and the hollow shaft to allow releasing the vacuum in the interior of the hollow shaft, in operation, by passing a gas through the vent conduit and vent opening.

[ 22 ] In an embodiment a housing plate is arranged in the housing transverse to the longitudinal axis of the hollow shaft on a wall of the main duct, the housing plate comprises a duct opening to the main duct end section, an area on a valve side of the housing plate around the duct opening provides the ridge against which the vacuum valve closes, a vent side of the housing plate opposite the valve side comprises a vent groove in fluid communication with the vent opening and the vent conduit in the housing, the seal is mounted between the housing plate and the housing, and the vent opening is provided by the vent groove opening in the main duct end section between the vent side and the seal, in which very efficiently a number of functions are combined.

[ 23 ] In an embodiment the vent groove comprises an annular vent groove section around the duct opening and at least one radial vent groove section that is radially directed from the annular vent groove section to the duct opening, and the annular vent groove section is in fluid communication with the vent conduit in the housing.

[ 24 ] In an embodiment a first rotation bearing for the hollow shaft is arranged in the housing to interact with the hollow shaft to confine movement of the hollow shaft in a direction along its longitudinal axis towards the distal end of the hollow shaft.

[ 25 ] In an embodiment a second rotation bearing for the hollow shaft is arranged in the housing to interact with the hollow shaft to confine movement of the hollow shaft in a direction along its longitudinal axis away from the distal end of the hollow shaft.

[ 26 ] In an embodiment the hollow shaft comprises a thickened section which has an externally protruding outside circumference that is protruding with respect to an outside circumference of sections of the hollow shaft on either side of the thickened section as seen along the longitudinal direction of the hollow shaft, and the first and second rotation bearings are arranged on either side of the thickened section against the thickened section, which provides for rotational freedom of the hollow shaft while confining movement along and transverse to its longitudinal axis.

[ 27 ] In an embodiment the first and second rotation bearings are arranged on opposing sides of the motor as seen along the longitudinal direction of the hollow shaft. [ 28 ] In an embodiment the housing comprises a motor part, in which the motor is arranged, and a valve part, in which the vacuum valve is arranged, both the motor part and the valve part of the housing having opposing first and second sides, and the second side of the motor part and the first side of the valve part being configured to match to allow assembly of the housing, and the distal end of the hollow shaft projects from the first side of the motor part of the housing.

[ 29 ] In an embodiment the vacuum valve is provided in a vacuum valve module in which the vacuum valve is mounted to allow moving the vacuum valve to its open and closed positions, the valve module is arranged in the valve part of the housing and has an actuation conduit, such as a compressed air connection, to allow actuation of the vacuum valve, and the actuation connection of the vacuum valve module is connected to an actuation connection, such as a compressed air connection with a switch valve, provided on the outside of the valve part of the housing.

[ 30 ] In an embodiment the first rotation bearing is arranged in the motor part of the housing between the motor and the first side of the motor part of the housing.

[ 31 ] In an embodiment the housing plate is provided in the valve part of the housing.

[ 32 ] In an embodiment the valve part of the housing comprises a cap part of the housing, in which the vacuum valve is arranged, and a central part of the housing, both the cap part and the central part of the housing having opposing first and second sides, the second side of the central part and the first side of the cap part being configured to match to allow assembly of the valve part of the housing, and the first side of the central part being the first side of the valve part of the housing.

[ 33 ] In an embodiment the housing plate is arranged on the second side of the central part of the housing, and a section of the main duct is provided between the valve in the open position thereof and the housing plate.

[ 34 ] In an embodiment the housing plate is attached to the second side of the central part of the housing.

[ 35 ] In another aspect the invention provides a delta robot comprising an end- effector as referred to above.

BRIEF DESCRIPTION OF THE DRAWINGS

[ 36 ] Further features and advantages of the invention will become apparent from the description of the invention by way of non-limiting and non-exclusive embodiments. These embodiments are not to be construed as limiting the scope of protection. The person skilled in the art will realize that other alternatives and equivalent embodiments of the invention can be conceived and reduced to practice without departing from the scope of the present invention. Embodiments of the invention will be described with reference to the accompanying drawings, in which like or same reference symbols denote like, same or corresponding parts, and in which

Figure 1 shows a delta robot having an end-effector according to the invention; Figures 2A and 2B show perspective views of an end-effector according to the invention;

Figure 3 shows a cross-section of the end-effector of figures 2A and 2B;

Figure 4 shows the cross-section of figure 3 taken apart in three parts; Figure 5 shows a perspective view on the end-effector of figures 2A, 2B, 3 and 4 taken apart in three parts;

Figures 6A and 6B show top and bottom views of the housing plate, respectively, ; and

Figure 7 shows a cross-sectional detail, as indicated by VII in figure 3, of the housing plate, PS seal and central part of the housing.

DETAILED DESCRIPTION OF EMBODIMENTS

[ 37 ] Figure 1 shows a delta robot 10 having an end-effector 100 according to the invention. The delta robot has three arms 11 that are each individually actuated by motors 12 for rotation and coupled to the end-effector to move the end-effector 100 around. Figures 2A and 2B shows the outside of the housing 110 of the end-effector 100 in more detail. Each arm 11 of the delta robot 10 is coupled to a respective pair of ball studs 119. The end-effector can be moved around in three dimensions very fast by individually actuating the three arms. The housing has a vacuum connection 115 for connecting to an external source of vacuum (not shown). The vacuum is passed through the end-effector to a hollow shaft 120 of the end-effector, of which the distal end 120.2 shows in figures 2A and 2B. The end-effector allows to rotate the hollow shaft 120 around its central longitudinal axis as well. A further device (not shown) can be mounted at the distal end 120.2 of the hollow shaft. Such further device can be a pick-up device for picking up products by vacuum suction. Switching of the vacuum allows products, or other objects, to be picked up and released again. Rotation of the hollow shaft 120 allows for a fourth degree of freedom for the pick-up device, being rotation about the longitudinal rotation axis of the hollow shaft.

[ 38 ] Referring to figures 2A, 2B, 3, 4 and 5, the housing 110 of the end-effector 100, in the embodiment shown, comprises a motor part 111 in which the motor 140 is arranged for driving rotational movement of the hollow shaft 120. The distal end 120.2 of the hollow shafts projects from the first side 111.1 of the motor part 111 of the housing 110. The motor 140 is an electrical motor having a stator 142 that is attached to the motor part 111 of the housing, and a rotor 141 that is attached to the hollow shaft 120. In the embodiment shown, the electrical motor 140 is a brushless torque motor having permanent magnets in the rotor 141 and electrical wiring coils in the stator 141. Such an electrical motor is known as such and allows for a position readout of the rotor through the electrical currents and voltages for the coils of the stator. This can be done by superposing an alternating voltage and measuring self-induction of the motor coils and measuring counter-electromotive force of the motor coils. These techniques are known as such and allow position readout without additional position sensors that would add volume and mass to the end-effector. The electrical wiring of the motor 140) is connected to an electrical motor connector 145 on the outside of the housing 110 for connection to an electrical drive cable. The rotor 141 is attached to a thickened section 122 of the hollow shaft 120 with a spacer element 143 in between. The thickened section 122 has an externally protruding wall that is protruding with respect to sections of the hollow shaft above and below the thickened section 122. The motor 140 is arranged around the longitudinal axis 120A and allows to rotate the hollow shaft around the longitudinal axis 120A of the hollow shaft 120.

[ 39 ] A first rotation bearing 125 for the hollow shaft is arranged inside the motor part 111 of the housing 110 between the first side 111.1 of the motor part and the thickened section 122 of the hollow shaft. The motor part 111 has opposing first and second sides 111.1 , 111.2 at its bottom and top ends, respectively, as shown in the figures. This configuration provides for a confinement of the movement of the hollow shaft 120 in a direction along its longitudinal axis 120A towards the distal end 120.2 of the hollow shaft. A second rotation bearing 126 for the hollow shaft is arranged on the other side of the thickened section 122 of the hollow shaft to interact with the hollow shaft to confine movement of the hollow shaft in a direction along its longitudinal axis 120A away from the distal end 120.2 of the hollow shaft. The arrangement of both the first and second rotation bearings 125, 126 on both sides of the thickened section 122 of the hollow shaft confines movement of the hollow axis 120 to a rotational movement about its longitudinal axis 120A only. The rotational bearings are arranged on both sides of the electrical motor as well as seen along the longitudinal direction of the hollow shaft. Rotational bearings are known as such.

[ 40 ] A vacuum valve 130 is arranged in the valve part 114 of the housing 110. The valve part has opposing first and second sides 114.1 , 114.2 at its bottom and top ends, respectively, as shown in the figures. The first side 114.1 of the valve part 114 matches the second side 111.2 of the motor part 111 of the housing to allow assembly of the housing into the configuration as shown in figures 2A, 2B and 3. In the embodiment shown in the figures, the valve part 114 of the housing is made up of a cap part 113 of the housing and a central part 112 of the housing. The central part 112 and the cap part 113 of the housing each have opposing first and second sides 112.1 , 113.1 , 112.2, 113.2, the first side 112.1 of the central part 112 being the first side 114.1 of the valve part 114. The vacuum valve 130 is mounted in a vacuum valve module 131 that is arranged and fixed in the cap part 114 by, for instance, screws.

[ 41 ] The vacuum valve module has an actuation conduit 132 for compressed air, which is connected to a valve actuation connection 135 in the form of a compressed air connection on the outside of the cap part 113. A valve actuation switch valve (not shown) can be provided in the valve actuation connection or elsewhere in a conduit connected to the valve actuation connection. In operation, a conduit for compressed air is connected to the valve actuation connection 135. The valve actuation switch valve can switch to pass the compressed air via the actuation conduit 132 to actuate the vacuum valve 130. In the embodiment shown the vacuum valve 130 is in the upward open position when the compressed air is switched off. When compressed air is provided to the vacuum valve 130 by switching the valve actuation switch valve to open, the vacuum valve 130 is actuated to a downward closed position. Figure 3 shows the vacuum valve 130 in the downward closed position thereof. Figure 4 shows the vacuum valve 130 in the upward open position. The vacuum valve 130, in the embodiment shown, is a circular plate of which the centre is aligned with the longitudinal axis 120A of the hollow shaft 120, and which can move up and down into the open and closed positions, respectively. The construction and mounting of the vacuum valve 130 is such in its vacuum module 131 that the vacuum valve is normally open when a pressure difference across the valve is below a threshold value.

[ 42 ] The second rotational bearing 126 is arranged on the second side 112.2 of the central part 112 of the housing such that it is confined between said second side 112.2, the outside circumference of the hollow shaft 120 and the thickened part 122 of the hollow shaft in the assembled state of the central part 112 on the motor part 111 of the housing. The proximal end 120.1 of the hollow shaft is inside the housing and projects from the second end 111 .2 of the motor part 111 of the housing into the central part 112 of the housing. The proximal end 120.1 of the central shaft has a proximal shaft opening 123 transverse to the longitudinal axis 120A of the hollow shaft. An annular PS seal 150 is arranged in a step on the second side 112.2 of the central part 112. A housing plate 160 is provided on said step on the second side 112.2 of the central part 112 to confine and mount the PS seal. The lip 151 of the PS seal seals against the outer circumference of the proximal end 120.1 of the hollow shaft. The other end of the PS seal is mounted on the wall of the main duct 116 of the housing.

[ 43 ] The housing plate 160 has a duct opening 163, and is shown in more detail in figures 6A and 6B. The duct opening 163 is circular and aligned with the proximal shaft opening 123. The longitudinal axis 120A of the hollow shaft passes through the centre of the duct opening 163. An upper valve side 160.2 of the housing plate 160 is directed to the vacuum valve 130. The area on the valve side 160.2 of the housing plate around the duct opening 163 provides for a ridge 161 on which the vacuum valve closes in the closed position of the vacuum valve 130 as is shown in figure 3 and in more detail in figure 7. The duct opening 163 in the housing plate 160 is closed by the vacuum valve 130 in the closed position thereof.

[ 44 ] A main duct end section 116E of the main duct 116 is defined below the vacuum valve in the closed position thereof in the embodiment shown. The main duct end section 116E is adjacent to the proximal shaft opening 123 and extends along the longitudinal axis 120A of the hollow shaft 120 to the vacuum valve 130. The vacuum valve closes on the main duct end section 116E. The main duct end section 116E effectively is an extension of the hollow interior of the hollow shaft 120. The housing plate 160 is arranged shortly above the proximal end 120.1 of the hollow shaft to leave a small clearance between the housing plate and the proximal end 120.1. The clearance keeps rotation of the hollow shaft free from frictional forces by the housing plate 160 since there is no contact. The PS seal 150 seals the gap between the wall of the main duct end section 116E and thus of the main duct 116 with the hollow shaft 120. The small clearance between the housing plate 160 and the proximal end 120.1 of the hollow shaft 120 also provides that the volume of the main duct end section 116E is small as compared to the volume of the hollow interior of the hollow shaft.

[ 45 ] The vent side 160.1 of the housing plate 160 opposite the valve side 160.2 comprises a vent groove 166 having an annular vent groove section 166.1 and radial vent groove sections 166.2 that extend from the annular vent groove section to the inner perimeter of the duct opening 163 in the housing plate. The housing plate 160 is arranged on the second side 112.2 of the central part 112 of the housing such that the annular vent groove section 166.2 is in fluid communication with a vent conduit 162 in de central part 112 of the housing. A vent connection 165 is provided on the outside of the central part 112 of the housing in fluid connection with the vent conduit 162. A vent switch valve can be provided in the vent connection 165 or in a conduit connected to the vent connection 165. The radial vent groove sections 116.2 together with the part of the PS seal 150 confined between the central part 112 of the housing and the housing plate 160 define a vent passage to multiple vent openings 164 into the main duct end section 116E, as is shown in more detail in figure 7.

[ 46 ] In operation, a conduit for compressed air is connected to the vent connection 165. The vent switch valve can switch to pass the compressed air via the vent conduit 162 to vent the main duct end section 116E and the hollow shaft 120. This will only be done when the vacuum valve 130 is in the closed position to close the main duct end section 116E and interior of the hollow shaft off from the vacuum connection 115. Figure 7 also shows an opening of a connection duct 155 between the inside of the housing behind the lip 151 of the PS seal 150 and the outside of the housing 110. The connection duct 155 keeps the inside of the housing behind the lip of the PS seal above the second rotational bearing 126 at atmospheric pressure to keep a proper sealing of the PS seal lip 151 against the outside perimeter of the hollow shaft 120 while the interior of the hollow shaft is under vacuum. Having atmospheric pressure at that location within the housing is also advantageous with respect to the functioning of the second rotational bearing 126.

[ 47 ] The main duct 116 extends from the vacuum connection 115 through the motor part 111 , the central 112 and the cap part 113 of the housing. When a vacuum source, such as a vacuum pump, is connected to the vacuum connection 115 the vacuum is present in the sections of the main duct 116 in the motor part 111 , central part 112 and cap part 113 of the housing 110 and also in the main duct end section 116E and the hollow interior of the hollow shaft in an open position of the vacuum valve 130, as is shown in figure 3. In operation a further device, such as a pick-up device, will be mounted on the distal end 120.2 of the hollow shaft 120 to pass the vacuum to the further device for use by the further device. Such further device is not shown in the figures.

[ 48 ] A main duct transverse section 116T that is adjacent the main duct end section 116E is transverse to the main duct end section when considering a gas flow direction through the main duct 116. Transverse should be understood to mean that with a gas flow through the main duct 116 that a gas flow direction through the main duct transverse section 116T is transverse to a gas flow direction through the main duct end section 116E. Both the main duct transverse section 116T and the main duct end section 116E are part of the main duct 116. A fluid connection between the main duct transverse and end sections of the main duct is present when the vacuum valve 130 is in the upward open position, as shown in figure 4. Such configuration allows closing off of the main duct end section 116E, and of the hollow interior of the hollow shaft 120, from the vacuum connection 115 through a downward movement of the vacuum valve 130 to its closed position. In addition to the volume of the hollow interior of the hollow shaft 120 only a small volume of the main duct end section 116E remains in fluid communication with hollow interior of the hollow shaft 120 for venting or evacuating thereof to operate the further device at the distal end 120.2 of the hollow shaft. Effectively, only the hollow interior of the hollow shaft 120 requires venting or evacuating to operate the further device.