Patent Description:
Individual packaging containers, such as liquid food packaging containers, are typically produced from a carton-based material and filled using a high-speed filling machine. When the filled, formed, and sealed packaging containers are unloaded from the filling machine they are typically transferred to a cardboard packer in which a predetermined number of packaging containers are stacked in a packing pattern and placed in a case made from a cardboard blank, or to a film machine or similar equipment that encloses groups of packaging containers.

During such manufacturing, there is a need to move the packaging containers from one location to another. For example, packaging containers need to be moved from the filling machine (or any conveyor associated thereto) to the cardboard packer (or any conveyor associated thereto).

In order to move packages from one area to another within industrial machine equipment, a robot arm can be used. The robot arm may be programmed to move in three dimensions with various degrees of freedom. At the distal end of the robot arm, a gripper is arranged providing an interface between the machine and the packaging container.

Such packaging container interfaces are traditionally mechanical grippers, or vacuum cup grippers that operate on the upper plane of the packaging container. However, prior art grippers do not provide the speed nor stability required for the cycle time that is typically needed, i.e. the time needed to perform one complete operation. In modern manufacturing, grippers must be able to perform a complete handling sequence in <NUM> second or less.

Further prior art is described in patent documents <CIT>, <CIT>, <CIT>, <CIT>.

Most constrains of prior art grippers bore down to the cycle time required. Problems stem from excessive robot movement being needed to accommodate the physical size and geometric requirements of a gripper. This includes positioning, activation, placing, release and careful withdrawal of the gripper in relation to the packaging container. Also, problems are related to excessive time required to evacuate the vacuum cups used to grip the packaging containers, as well as to excessive time needed to ensure that the vacuum has been completely broken so as not to disturb the packaging containers as the gripper retreats.

There is thus a need for an improved gripper unit, providing more robust, more accurate, and faster positioning of packaging containers.

It is an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to provide a gripper unit which reduces any "pushing action" on the packaging container once the vacuum is removed for releasing the packaging container from the gripper unit.

According to a first aspect, gripper unit is provided. The gripper unit comprises a vacuum distribution unit connected to a housing such that linear motion of the vacuum distribution unit is allowed in a first direction towards and away from the housing. This improves accuracy of the gripper unit. The gripper unit comprises at least a first leaf spring connecting the vacuum distribution unit to the housing.

The gripper unit further comprises at least one additional leaf spring connecting the vacuum distribution unit to the housing.

The at least one additional leaf spring has substantially the same length as the first leaf spring.

The at least one additional leaf spring is arranged in parallel with the first leaf spring, but spaced apart in the first direction. Hence, rotation of the vacuum distribution unit is prevented in a plane defined by a central axis of the first leaf spring and a central axis of the additional leaf spring.

The gripper unit comprises two additional leaf springs arranged on opposite sides of the first leaf spring. Symmetry is thereby achieved.

The gripper unit may comprise a plurality of gripper units according to the first aspect. In such embodiment it is possible to move a plurality of packaging containers using a single robotic arm.

The gripper unit comprises at least one vacuum suction cup. The at least one suction cup is moveable between an idle position in which the at least one suction cup is arranged completely within a housing of the gripper unit, and an active position in which the at least one suction cup is extending out from said housing.

The gripper unit comprises at least two suction cups operating in the same plane and being jointly movable between the idle position and the active position. Improved gripping of the packaging container is thereby achieved.

The position of the at least one suction cup may be controlled using vacuum, which allows for the use of readily available and high quality vacuum generators.

The gripper unit further comprises a control suction cup. Activation of the control suction cup may urge the at least one suction cup to move from the idle position to the active position, which is advantageous in that a common air supply can be utilized for the attaching suction cups and for the control suction cup.

The control suction cup may be arranged inside a cavity of the housing, wherein said cavity is closed by a lid against which the control suction cup will apply a vacuum.

According to a second aspect, a robotic arm assembly is provided. The robotic arm assembly comprises a robot arm, such as an articulated robot arm or a delta robot, and at least one gripper unit according to the first aspect being provided on the robot arm.

Starting in <FIG>, a robotic arm assembly <NUM> according to an embodiment is schematically shown. The robotic arm assembly <NUM> comprises a robotic arm <NUM> and a gripper unit <NUM>, whereby the gripper unit <NUM> is provided on the distal end of the robotic arm <NUM>. Preferably, the robotic arm <NUM> is an articulated delta robot, or an articulated robot having at least three rotary joints. Articulated robots, as well as delta robots, are well known in the art and will not be described further herein.

The robotic arm assembly <NUM> is arranged in a machine environment, such as between a filling machine and a cardboard packer (not shown) or other type of equipment. In such example, the robotic arm assembly <NUM> is provided in order to move individual packaging containers <NUM>, being produced by the filling machine and discharged therefrom by means of a conveyor <NUM>. The packaging containers <NUM>, which typically have a main body <NUM> including at least one planar panel <NUM>, are gripped by the robotic arm assembly <NUM> as they are transported on the conveyor <NUM>, and moved to a feeding conveyor <NUM> of the cardboard packer to be transported to further equipment downstream the conveyor <NUM>. It should be noted that the planar panel <NUM> of the main body <NUM> must not necessarily form an entire side of the packaging container <NUM>, but should preferably be a planar surface big enough to be gripped by the gripper unit <NUM>.

The robotic arm assembly <NUM> is configured to operate at very high speed; from an idle position, it must be capable of performing the following motion sequence: arranging the gripper unit <NUM> in close proximity to the approaching packaging container <NUM>, to activate the gripper unit <NUM> in order to attach the packaging container <NUM> to the gripper unit <NUM>, to move the gripper unit <NUM> and the attached packaging container <NUM> to the desired position, to release the packaging container <NUM> by deactivating the gripper unit <NUM>, and to return to the idle position. The complete motion sequence should typically be performed in less than <NUM> second, such as below <NUM> seconds, even more preferably below <NUM> seconds.

A controller <NUM> is therefore provided and connected to the gripper unit <NUM> in order to control activation and deactivation of the gripper unit <NUM>. In some embodiments, the controller <NUM> is also in communication with the robotic arm <NUM>.

The controller <NUM> preferably comprises a non-transitory computer-readable storage medium, storing one or more programs configured for execution by one or more processors, the one or more programs comprising instructions for controlling the gripper unit <NUM>.

Now turning to <FIG> further details of the gripper unit <NUM> are shown. The gripper unit <NUM> is a vacuum gripper unit <NUM> being capable of attaching an adjacent packaging container by applying a suction force using one or more vacuum cups <NUM>.

The gripper unit <NUM> comprises a housing <NUM> and a vacuum distribution unit <NUM>. The vacuum distribution unit <NUM> is moveable in relation to the housing <NUM>, and comprises at least one suction cup <NUM>. In the shown example, the vacuum distribution unit <NUM> comprises two spaced apart suction cups <NUM> for attaching to the packaging container by applying vacuum, and one control suction cup <NUM>.

All suction cups <NUM>, <NUM> are preferably activated simultaneously. This is particularly the case when the suction cups <NUM>, <NUM> share a common air supply (as will be described later). By activation of the suction cups <NUM> and the control suction cup <NUM>, the vacuum distribution unit <NUM> is moved towards the housing <NUM>, in the direction indicated by the block arrow in <FIG>. Hence, the vacuum distribution unit <NUM> is moved from an idle position (shown in <FIG>) to an active position (shown in <FIG>). When the vacuum distribution unit <NUM> is in the active position, the suction cups <NUM> are arranged in an extended position, i.e. the distal end of each suction cup <NUM> is arranged outside the housing <NUM>.

In the active position, as shown in <FIG>, the gripper unit <NUM> is ready to grip a packaging container. As vacuum is applied, upon activation of the suction cups <NUM>, <NUM>, a suction force is generated in each suction cup <NUM>, <NUM> thereby pulling the packaging container, as shown in <FIG> towards the housing <NUM>. Due to the flexible material of the suction cups <NUM>, the planar panel <NUM> of the packaging container will be in contact, and flush with, the housing <NUM>.

The gripper unit <NUM> is used to collate individual packaging containers while they are in motion, necessitating the activation of the suction cups <NUM>. The vacuum operated suction cups <NUM> need to interfere with the packaging containers that they are picking in order to attain a seal, and therefore a robust grip.

Should the suction cups <NUM> stand out of the housing <NUM> (and ready to contact a packaging container), it would possibly impede the collection of the packaging container. Thus, the gripper unit <NUM> described herein is configured to retract the suction cups <NUM>, leaving a "clean" housing surface that does not impede packaging container movement.

In fact, the suction cups <NUM> are controlled to protrude to ensure the suction cups <NUM> meet the packaging container before the housing <NUM>. The suction cups <NUM> are retracted by cutting off air supply to the vacuum generators <NUM>, <NUM> (see <FIG>), in order to ensure the suction cups <NUM> do not interfere with packaging containers being placed.

In the embodiment shown in <FIG>, three vacuum cups <NUM>, <NUM> are employed and mounted together on the common vacuum distribution unit <NUM>. Two suction cups <NUM> are configured to grip the packaging container <NUM>, and the third suction cup <NUM> acts as an actuator to pull the vacuum distribution unit <NUM> forwards.

During operation, placement of the packaging container will be stable as the suction cups <NUM> withdraw from the packaging container, into the housing <NUM>, as the vacuum is released. This is achieved by de-activating the control suction cup <NUM> and the suction cups <NUM> simultaneously, whereby the vacuum distribution unit <NUM> is allowed to return to its idle position of <FIG>.

Now turning to <FIG>, some further details of the gripper unit <NUM> will be described. The suction cups <NUM> used to attach to the packaging container <NUM> are connected to a common vacuum generator <NUM> (seen in <FIG>), forming part of the vacuum distribution unit <NUM>. Preferably, the vacuum generator <NUM> is designed for porous material, thus being capable of generating high flow and low vacuum. This will reduce the grip time, and ensure that the packaging material of the packaging container <NUM> is undamaged.

As shown in <FIG>, the control suction cup <NUM> is arranged inside a cavity <NUM> of the housing <NUM>, wherein the cavity <NUM> is closed in the plane of the surface of the housing <NUM> by means of a lid <NUM>. When the control suction cup <NUM> is activated, preferably by means of a separate vacuum generator <NUM> (see <FIG>), the vacuum will pull the entire vacuum distribution unit <NUM> towards the housing <NUM> as the control suction cup <NUM> applies the suction force against the inside of the lid <NUM>. This is shown in <FIG>, where the distal end of each suction cup <NUM> extends out from the housing <NUM> to some extent. Once the vacuum is released from the control suction cup <NUM>, the suction cups <NUM> will return to their withdrawn position as indicated in <FIG> due to the return movement of the entire vacuum distribution unit <NUM>.

Still referring to <FIG>, while the housing <NUM> forms a static frame and a robust connection to the robotic arm <NUM> (see <FIG>), the vacuum distribution unit <NUM> comprises a rigid frame <NUM> to which the suction cups <NUM>, the control suction cup <NUM>, vacuum generators <NUM>, <NUM>, and an air supply connection <NUM> (see <FIG>) are mounted. Yet further, the vacuum distribution unit <NUM> may be provided with a vacuum transducer <NUM> in order to allow for condition monitoring of the suction cups <NUM>, or to ensure that a "grip" has been attained between the gripper unit <NUM> and the packaging container <NUM>.

The vacuum generators <NUM>, <NUM> may share a common air supply <NUM>, thus making the connection of the gripper-unit <NUM> both simple and fast when change-overs or replacements of components are needed. As can be further seen in the drawings, the vacuum generators <NUM>, <NUM> and the suction cups <NUM>, <NUM> are placed in extreme proximity, thereby reducing the reaction times for pick and place of packaging containers <NUM>.

An additional advantage of the gripper unit <NUM> is that the low-profile design allows the gripper unit <NUM> to work in close proximity to other packaging containers without causing crashes or collisions, and again reducing cycle time.

The gripper unit <NUM> reduces lost time by creating high-flow low-vacuum at the exact point of need, in a design that is dimensioned to reduce air consumption, and to reduce areas that are subjected to the vacuum. These features reduce the time needed to create a positive bond between the gripper unit <NUM> and an adjacent packaging container <NUM>, and similarly reduce the time needed to release the bond.

In a preferred embodiment, the gripper unit <NUM> has no sliding or rotating parts; the lifetime will benefit from this. However, the vacuum distribution unit <NUM> should be allowed to move relative the housing <NUM> as explained above. Even more preferably, the vacuum distribution unit <NUM> should also be allowed to automatically return to its idle position once the control suction cup <NUM> is de-activated.

Accordingly, a gripper unit <NUM> is proposed where a housing <NUM> is connected to a vacuum distribution unit <NUM> in a way that allows for a linear motion of the vacuum distribution unit <NUM> towards and away from the housing <NUM>, while at the same time preventing movement of the vacuum distribution unit <NUM> in any other direction.

An embodiment of such connection is shown in <FIG>. A first leaf spring <NUM> interconnects the housing <NUM> and the vacuum distribution unit <NUM>. The first leaf spring <NUM> provides a resilient suspension allowing movement in the directions of the planar surfaces of the leaf spring <NUM> (up or down in the view of <FIG>), and it also provides a suspension which is rigid in the cross directions of these planar surfaces.

The first leaf spring <NUM> is arranged at an inner part of the gripper unit <NUM>, facing the robotic arm <NUM> during use, connecting the housing <NUM> to the rigid frame <NUM> of the vacuum distribution unit <NUM>.

Two additional leaf springs <NUM> are also provided, spaced apart from the first leaf spring <NUM>. The two additional leaf springs <NUM> (of which only one is shown in <FIG>) are arranged at a level closer to the suction cups <NUM>, as indicated in <FIG>. All leaf springs <NUM>, <NUM> are arranged in parallel. One of the additional leaf springs <NUM> is extending approximately in a direction being aligned with the longitudinal direction of the vacuum generator <NUM>, while the other of the additional leaf springs <NUM> is extending approximately in a direction being aligned with the longitudinal direction of the vacuum generator <NUM> (see <FIG>, in which the two additional leaf springs <NUM> are visible).

The motion of the vacuum distribution unit <NUM> is physically constrained by leaf springs <NUM>, <NUM>, which protect the vacuum distribution unit <NUM> against overtravel. The housing <NUM> is provided with two spaced apart T-shaped members <NUM> which form stop surfaces for the vacuum distribution unit <NUM> during activation and de-activation of the suction cups <NUM>, <NUM>. Due to the arrangement of the leaf springs <NUM>, <NUM>, the motion is guided in a pure longitudinal direction by use of the leaf springs <NUM>, <NUM> disposed in a parallelogram configuration.

The beneficial effects of the first leaf spring <NUM> are thereby enhanced by the arrangement of the additional leaf springs <NUM> interconnecting the vacuum distribution unit <NUM> and the housing <NUM>. The arrangement of the additional leaf springs <NUM> further reduces the freedom of movement of the vacuum distribution unit <NUM>, such that it may essentially only move up and down in the first direction, as limited by a constant radii provided by each leaf spring <NUM>, <NUM>.

In particular, the addition of the additional leaf springs <NUM> reduces any torsion along the length direction of the primary leaf spring <NUM> or any bending of the leaf spring <NUM>. Furthermore, arranging essentially equally long leaf springs <NUM>, <NUM> in parallel but separated in the motion direction, provides a means of maintaining the orientation of the vacuum distribution unit <NUM>, meaning that the vacuum distribution unit <NUM> is prevented from rotating.

In <FIG> an example of implementation of gripper units <NUM> is shown. A gripper unit assembly <NUM> comprises at least one gripper unit <NUM>, in this embodiment three gripper units <NUM> are arranged in parallel, and mounted together. Preferably, the gripper units <NUM> are arranged in a common housing (not shown) so that the robotic arm <NUM> (see <FIG>) can be connected to the common housing. Hence, the gripper unit assembly <NUM> can be used to move three packaging containers at the same time, as long as the packaging containers are positioned relative each other so that they fit with the dimensions of the gripper unit assembly <NUM>.

Now returning to <FIG> an embodiment of a gripper unit <NUM> is shown in cross-section. In particular, <FIG> shows how the first vacuum generator <NUM> is connected to both suction cups <NUM> by means of a common fluid channel <NUM>. As can be seen, the vacuum transducer <NUM> is also connected to the common fluid channel <NUM> so that the vacuum level can be measured accurately. The second vacuum generator <NUM> is connected to the control suction cup <NUM> via a control fluid channel <NUM>.

Now turning to <FIG>, a method <NUM> for a gripper unit <NUM> is schematically shown. In a first step <NUM>, the gripper unit <NUM> is activated to move at least one suction cup <NUM> out from a housing <NUM>, so that the at least one suction cup <NUM> protrudes from the housing surface. In a next step <NUM> the at least one suction cup <NUM> is positioned close to a packaging container <NUM>, and gripping the packaging container <NUM> because of the applied vacuum. In a final step <NUM>, the gripper unit <NUM> is deactivated thereby pulling the at least on suction cup <NUM> back into the housing, and the at least one suction cup <NUM> is also deactivated simultaneously to release the vacuum and hence also the grip of the packaging container <NUM>.

Claim 1:
A gripper unit (<NUM>), comprising a housing (<NUM>) and a vacuum distribution unit (<NUM>) connected to the housing (<NUM>) such that linear motion of the vacuum distribution unit (<NUM>) is allowed in a first direction towards and away from the housing (<NUM>), wherein the gripper unit (<NUM>) comprises:
- at least a first leaf spring (<NUM>) connecting the vacuum distribution unit (<NUM>) to the housing (<NUM>);
- at least one vacuum suction cup (<NUM>), wherein the at least one suction cup (<NUM>) is moveable between an idle position in which the at least one suction cup (<NUM>) is arranged completely within the housing (<NUM>) of the gripper unit (<NUM>), and an active position in which the at least one suction cup (<NUM>) is extending out from said housing (<NUM>),
wherein the position of the at least one suction cup (<NUM>) is controlled using vacuum,
characterized by further comprising a control suction cup (<NUM>).