Patent Description:
The challenge associated with handling limp material such as textile articles is that the limp material does not have a defined shape. As a simple example, a tablecloth can have a spread out, rectangular shape, or it can be present in the form of a rather small, crumpled bundle. Any attempt to handle limp material in an automated manner requires bringing the limp material into a defined shape or at least positively identifying specific points of the limp material such as the edges.

The term "limp material" here refers to products for human necessities such as textile articles, in particular clothes, and to industrial products such as panels, covers or fibre mats. It further includes paper, sheets of foil material, and knitted articles. These examples are not exhaustive.

One example of a machine for handling limp material can be found in <CIT>. The machine comprises two grippers which engage at a textile article at two points space from each other. The grippers can bring the textile article into a defined shape for further processing.

A machine with the features of the preamble of claim <NUM> is known from <CIT>.

The object of the invention is to improve the handling capabilities of machines which are used for handling limp material.

In order to achieve this object, the invention provides a machine for handling limp material with the features of claim <NUM>. The invention is based on the idea of adding additional functionality to the grippers which are known from the prior art. In the prior art, the limp material at which the gripper engages can be made to slide within the gripper when sufficient traction force is exerted on the limp material. The displacement mechanism which is provided according to the invention in the manipulator, allows controlling the sliding movement of the limp material within the manipulator. According to the invention, a receiving space is indeed provided between the base part and the pressing part, the receiving space being adapted for receiving an edge portion of the limp material and a sensor being arranged so as to detect the position of the edge portion within the receiving space.

In particular, the displacement mechanism allows actively moving the textile article with respect to the manipulator. It is therefore possible to make the limp material slide into a specific position with respect to the manipulator. In advanced embodiments, it is possible to make the manipulator follow a non-straight contour of the limp material so as to arrive at a position or specific point of the limp material which is beneficial regarding subsequent handling. The base part and the pressing part being displaceable with each other allow loading the limp material into the manipulator and clamping it therein with a predetermined and/or controllable force. It is also conceivable that the base part and the pressing part are displaceable with respect to each other by a predetermined and/or controllable distance. This avoids the necessity of force measurement. A wheel is particularly suitable for generating a sliding movement of the limp material with respect to the base part, with the extent of the sliding motion being easily controllable by the amount of rotation of the wheel. Assuming that it was possible to place the limp material with an edge within the receiving space, the position of the edge within the receiving space is particularly suitable for controlling a sliding displacement of the limp material by means of the wheel.

In a particularly simple embodiment, the displacement wheel is an omniwheel. The omniwheel can make the limp material slide with respect to the base part in a direction which is tangentially with respect to the omniwheel while at the same time allowing a low friction displacement in a direction which is parallel to the axis of rotation of the omniwheel.

In order to increase the friction between the wheel and the limp material, a guiding groove associated with the displacement wheel can be provided in the pressing part.

The sensor can be formed from discrete sensing elements arranged spaced from each other. The distance between the discrete sensing elements can be considered as a tolerance band in which the edge of the limp material should be. The discrete sensing elements allow detecting whether or not the edge is between the sensing elements. Should this not be the case, the limp material can be made to slide inwardly or outwardly by suitably rotating the displacement wheel until the edge is brought back to the desired position.

In one embodiment of the invention, a pair of displacement wheels is provided. Using a pair of displacement wheels allows for a better control of the displacement of the limp material with respect to the manipulator.

The pressing part can comprise a pair of pressing wheels and a pressing element, the pressing wheels and the pressing elements being moveable independently from each other with respect to the displacement wheels, particularly in a direction which is perpendicularly with respect to the plane in which the limp material is held between the displacement wheels. The force with which the limp material is clamped between the displacement wheels and the pressing wheels can be controlled via the displacement of the pressing wheels. Further, the pressing wheels and the pressing element can be retracted so as to allow for a loading and unloading of the limp material.

In one embodiment, the base part can be rotated around an axis which is perpendicular to the axis of rotation of the displacement wheels. Rotating the base part allows making the direction in which the limp material is displaced with respect to the base part consistent with the direction in which a contour or an edge of the limp material extends.

Preferably, the sensor is configured for detecting the presence of the limp material in a sensing area extending circumferentially around the base part, thereby providing the necessary information for sliding the limp material in the desired direction with respect to the base part.

Preferably, the sensor is formed from a plurality of discrete sensing elements arranged circumferentially around the base part. It is not necessary to have the sensor continuously monitor the circumference of the base part. Rather, it is sufficient to obtain the information in which sector of the circumference the limp material is present and in which it is not.

The sensor can also be formed from a camera system associated with an image recognition system adapted for evaluating the information provided by the camera and to extract therefrom the position of the limp material.

Instead of using a wheel for achieving a displacement of the limp material, any other element suitable for sliding the limp material with respect to the base part can be used. Examples are belts, translationally moveable pusher elements, reciprocating yaws, etc..

In one embodiment, the machine has two of the manipulators provided with at least one displacement wheel. The use of two manipulators allows for processing limp materials with a more complex outer contour and to displace the limp material with respect to the manipulator so as to reach predefined points of the limp material.

In one embodiment, the drive system comprises a linear drive on which the gripping devices are mounted, the linear drive being adapted for displacing the gripping devices from a loading position in which they are close to each other to a position in which they are spaced from each other, and vice versa. The linear drive is a mechanically simply and reliable system for obtaining the desired displacement of the gripping devices with respect to each other.

In an alternative embodiment, the drive system comprises two robot arms, each of them being provided with one gripping device, the robot arms being adapted for displacing the gripping devices from a loading position in which they are close to each other to a remote position in which they are spaced from each other, and vice versa. The robot arms assist the gripping devices in processing limp materials having a more complex contour, in particular a contour which is not only composed of a few straight portions.

The invention will now be explained with reference to the embodiments shown in the enclosed drawings. In the drawings,.

In <FIG>, a machine <NUM> for handling a limp material <NUM> is schematically shown. By way of example, the limp material will in the following be a textile article. It is to be kept in mind that the invention is applicable to any kind of limp material.

Machine <NUM> comprises two gripping devices <NUM>, each of the gripping devices being adapted for receiving and holding the textile article <NUM> which is currently being handled.

The two gripping devices <NUM> are mounted to a drive system <NUM> with which the gripping devices <NUM> can be displaced with respect to each other. As can be seen by comparing <FIG>, drive system <NUM> allows for displacing gripping devices <NUM> from a loading position which is shown in <FIG> and in which the gripping devices <NUM> are arranged close to each other or even in contact with each other, to a position shown in <FIG> in which the gripping devices <NUM> are at a distance from each other.

Drive system <NUM> can in particular be a linear drive which allows displacing the two gripping devices in the direction of arrows A away from each other, and vice versa. It is of course possible to arrange of the gripping devices stationary and to displace only the other gripping device <NUM>.

In the loading position, the textile article <NUM> is loaded to the gripping devices <NUM>. By displacing the gripping devices <NUM> away from each other, the textile article is stretched and tensioned, with the edge of the textile article <NUM> received within the gripping devices <NUM> sliding through the gripping devices.

In <FIG>, a second embodiment of machine <NUM> for handling textile articles <NUM> is shown.

The difference between the first and the second embodiment is that the second embodiment uses robot arms <NUM> as the drive system for moving the gripping devices <NUM> with respect to each other.

In a variation of the second embodiment, it is possible to use one gripping device <NUM> which is mounted stationary, and to displace only the second gripping device <NUM> with respect to the stationary gripping device.

In a still further variation, it is possible to use one of the gripping devices <NUM> as a simple gripper which simply fixes a corner of the textile article placed there, and the other gripper <NUM> is displaced away from the first gripper and follows the contour of the edge.

In <FIG> and <FIG>, a first embodiment of a gripping device <NUM> is shown. As the gripping device of <FIG> and <FIG> is able to actively slide the textile article with respect to the gripping device (in addition to allowing for a passive sliding movement in response to a displacement of the gripping devices with respect to each other), the gripping device of <FIG> and <FIG> is referred to as a manipulator.

Manipulator <NUM> has a base part <NUM> and a pressing part <NUM>. Base part <NUM> and pressing part <NUM> can be displaced with respect to each other as indicated by arrow D between a receiving position in which they are spaced from each other, and a clamping position in which they are approached to each other such that the textile article <NUM> is clamped in the gap between base part <NUM> and pressing part <NUM>.

Gripping device <NUM> is provided with a displacement mechanism <NUM> adapted for actively displacing the textile article in a direction which is generally within a plane in which the textile article is held in the manipulator. Looking at <FIG>, this plane is perpendicular with respect to the plane of the drawing and extends horizontally.

Displacement mechanism <NUM> comprises a displacement wheel <NUM> which is here rotatably mounted in base part <NUM>. As can be seen in <FIG>, a portion of displacement wheel <NUM> protrudes over the surface of base part <NUM> which faces pressing part <NUM>. In the position of base part <NUM> with respect to pressing part <NUM> as shown in <FIG> and <FIG>, the protruding portion of displacement wheel <NUM> engages into a guiding groove <NUM> formed in pressing part <NUM>.

Displacement wheel <NUM> can be made to actively rotate in either direction by means of a motor element <NUM> schematically shown in <FIG>.

The gap between base part <NUM> and pressing part <NUM> which is inside of displacement wheel <NUM> forms a receiving space <NUM> for an edge of the textile article <NUM> received between base part <NUM> and pressing part <NUM> (please see <FIG> in which the textile article <NUM> is schematically shown).

A sensor <NUM> is associated with the gripping device <NUM>, adapted for detecting the position of the edge of the textile article <NUM>.

In the embodiment shown in <FIG>, sensor <NUM> is formed from discrete sensing elements arranged spaced from each other in the direction of arrow T which designates a tolerance band in which the edge of textile article is supposed to be.

Sensing elements <NUM> can pairwise form for example a light barrier so that the presence of the textile article <NUM> can be detected.

Even though the space inwardly of the displacement wheel <NUM> is referred to as a receiving space for an edge of the textile article <NUM>, the space can, in a first step, receive any portion of the textile article <NUM>, e.g. a centre portion when the textile article is "thrown over" base part <NUM> in a condition in which pressing part <NUM> and base part <NUM> have been moved apart for receiving textile article <NUM>. After placing textile article over base part <NUM>, the textile article is manipulated until its edge is detected by sensor <NUM>.

Displacement wheel <NUM> is here formed as an omniwheel. It is therefore possible to displace textile article <NUM> in the direction of arrow T by rotating displacement wheel <NUM> in a clockwise or counter-clockwise direction with respect to <FIG>, while at the same time allowing the textile article <NUM> to be displaced in a direction which is perpendicular to the plane of <FIG>, for example by increasing the distance between the two gripping devices <NUM>.

With reference to <FIG> and assuming that each of the gripping devices <NUM> is provided with a displacement mechanism <NUM>, the edge of textile article <NUM> can be controlled, during the step of moving apart the gripping devices <NUM>, by suitably controlling the displacement mechanism so as to displace the portion of the textile article gripped within the gripping devices, in the direction of arrow T. The extent of displacement of textile article <NUM> can very easily be controlled with sensor <NUM> which detects the position of the edge of textile article <NUM>. As can be seen in <FIG>, the information that both pairs of sensing elements <NUM> are blocked by textile article <NUM> can be interpreted as the textile article <NUM> to be too far inwardly in the receiving space <NUM>, resulting in a counter-clockwise movement of displacement wheel <NUM> until the inner sensing element <NUM> does not longer detect the presence of the textile article. The information that both sensing elements <NUM> do not detect the textile article can be interpreted as the textile article being not sufficiently within receiving space <NUM>, resulting in a clockwise rotation of displacement wheel <NUM> until the outer sensing element <NUM> again detects the presence of the textile article.

A second embodiment of gripping devices <NUM> formed as manipulators is shown in <FIG>. For components known from the first embodiment, the same reference numerals are used, and reference is made to the above comments.

While the first embodiment uses a gripping device in the form of two jaws cooperating with each other, the second embodiment has a post-like or pillar-like base <NUM> with which the pressing part <NUM> cooperates. A further difference between the first and the second embodiment is that the second embodiment uses two displacement wheels <NUM> instead of a single displacement wheel.

Displacement wheels <NUM> are mounted rotatably within base part <NUM>. They can be actively driven by means of a motor which is not shown here. The motor is adapted for rotating both displacement wheels <NUM> in the same direction and with the same speed of rotation. As an example, both displacement wheels can be fixedly connected to one and the same drive shaft.

In order to increase the friction with the textile article to be displaced, displacement wheels <NUM> can be provided with a suitable configuration at their outer circumference. As shown in <FIG>, displacement wheels <NUM> here have a plurality of teeth.

As an alternative to teeth, the displacement wheels <NUM> can be provided with a rubber coating or any other surface which promotes friction between the displacement wheels and the textile article.

Pressing part <NUM> comprises two pressing wheels <NUM> arranged to cooperate with displacement wheels <NUM>. Pressing wheels <NUM> have a serrated circumference.

Pressing part <NUM> furthermore comprises a pressing element <NUM> which can be displaced independent from pressing wheels <NUM> towards base part <NUM> and away therefrom. Pressing element <NUM> here has a spherical surface which is adapted to cooperate with a guiding recess <NUM> in base part <NUM>. (please see <FIG>).

Gripping device <NUM> as shown in <FIG> is configured for receiving and clamping the textile article in a plane P which is schematically shown in <FIG>. By rotating the displacement wheels <NUM>, textile article <NUM> can be displaced in this plane P in a direction which is a tangent to the outer circumference of displacement wheels <NUM>. In other words, textile article <NUM> can be displaced, when looking at <FIG>, in a direction which is perpendicular to the plane of the drawing.

For loading the textile article <NUM> to gripping device <NUM>, pressing part <NUM> and pressing element <NUM> are retracted. When the textile article is placed over base part <NUM>, pressing part <NUM> is lowered into the position shown in <FIG>. In this position, the textile article is clamped between displacement wheels <NUM> and pressing wheels <NUM>. Accordingly, rotating the displacement wheels <NUM>, results in a displacement of the textile article with respect to base part <NUM>.

When the orientation of the textile article with respect to base part <NUM> is to be changed, pressing element <NUM> is lowered so as to clamp the textile article between the pressing part and the guiding recess <NUM>, while pressing part <NUM> is moved upwardly (please see <FIG>). In this condition, the textile article can be rotated with respect to base <NUM> by overcoming the (reduced) frictional forces between pressing element <NUM> and guiding recess <NUM>. When the textile article has been brought into the desired position, pressing part <NUM> is lowered so as to again clamp the textile article between the displacement wheels and the pressing wheels, and pressing element <NUM> can be retracted.

Changing the orientation of the textile article allows "navigating" to a desired point on the textile article, for example by displacing the textile article in different directions with respect to base part <NUM>.

<FIG> shows a schematic view of the base part <NUM> and a textile article <NUM>, with the pressing part <NUM> not being shown here for better clarity.

At base part <NUM>, some of the plurality of sensor elements <NUM> forming in their entirety the sensor, is shown. Sensing elements <NUM> are arranged circumferentially around base part <NUM>.

In a manner similar to the first embodiment, sensor <NUM> is formed from a plurality of discrete sensing elements <NUM>. These are spaced in equal intervals around base part <NUM>.

Discrete sensing elements <NUM> allow detecting the position and the orientation of textile article <NUM>, in particular the position of an edge E of textile article <NUM>. Assuming that textile article <NUM> is randomly placed over base part <NUM> at the beginning of the handling process, all sensing elements <NUM> are covered. By rotating displacement wheels <NUM>, textile article is displaced with respect to base part <NUM> in a direction which is designated in <FIG> with arrow <NUM>.

At a certain point, textile article <NUM> will be displaced so far that some of the sensing elements <NUM> are exposed. This condition is shown in <FIG> where four of the sensing elements <NUM> are shown as exposed. Assuming that edge E is straight, the orientation of edge E can be determined as being perpendicular to a line <NUM> which forms the centre of the sector <NUM> defined by exposed sensing elements <NUM>.

It is apparent that the sensing accuracy is the higher the more sensing elements are provided around the circumference of base part <NUM>.

If the orientation of edge E has been determined and it is further intended to displace textile article <NUM> along edge E, the direction of displacement of textile article <NUM> has to be made parallel to edge E. In the condition shown in <FIG>, these two directions are not yet parallel. The actual direction of displacement is designated with arrow <NUM> while the direction of edge E (designated with arrow <NUM>) is not parallel to direction <NUM>.

In a first step, pressing part <NUM> is retracted after pressing element <NUM> has been lowered so as to press textile article <NUM> against base part <NUM>. Then, either textile article <NUM> is rotated with respect to base part <NUM> in the direction of arrow <NUM> until the orientation of edge E is parallel to the displacement direction <NUM>. This can be achieved with a second gripping device which engages at textile article <NUM>. In the alternative, textile article <NUM> is held stationary and base part <NUM> is rotated in the direction of arrow <NUM> with respect to textile article <NUM>.

Once the orientation of edge E of textile article <NUM> is parallel with the displacement direction <NUM> defined by displacement wheels <NUM> in base part <NUM>, textile article <NUM> can be further displaced with respect to base part <NUM> while the position of edge E with respect to base part <NUM> is continuously monitored with sensor <NUM>. A change of the sector of sensing elements <NUM> not covered by textile article <NUM> indicates that the textile article <NUM> is displaced in a direction which is not parallel to its edge E. Accordingly, further intervention is necessary.

Another way of changing the orientation of textile article <NUM> with respect to base part <NUM> is to use a drive which is adapted for rotating the two displacement wheels <NUM> either in opposite directions or independent from each other so that textile article <NUM> can be rotated around an axis which is arranged between the two displacement wheels <NUM> or around an axis which is arranged outside the two displacement wheels.

For rotating textile article <NUM>, the displacement wheels <NUM> are driven in the required manner (e.g. opposite to each other). In this embodiment, pressing element <NUM> can be dispensed with.

In a still further variant, the displacement wheels <NUM> can be formed as omniwheels, allowing a displacement of textile article <NUM> in a direction which is oblique or transverse to the direction of advancement of the textile article defined by the rotation of the displacement wheels.

In a yet further embodiment, base part <NUM> comprises a set of displacement wheels <NUM> of the type shown in <FIG> (which drive textile article in a direction defined by the orientation of the axis of rotation of displacement wheels <NUM>) and an omniwheels (or two omniwheels) which allow for a lateral displacement of textile article. The different types of displacement wheels are mounted at base part <NUM> moveable between a retracted position and an active position so that one of the types of displacement wheels is in an active position while the other type is in the retracted position. This allows changing between two different modes of operation, one with a defined direction of displacement of textile article <NUM> and the other with a possibility of lateral displacement of textile article <NUM> in addition to the displacement generated by rotation of the omniwheels(s).

<FIG> shows an embodiment of a machine in which two of the manipulators shown in <FIG> are used, which are here mounted to a robot arm <NUM> each having six degrees of freedom. The robot arms form drive system <NUM>.

The starting position is shown in continuous lines on the left side of <FIG>. Both gripping devices <NUM> are placed close to each other, and the textile article is gripped between the two gripping devices <NUM>. After the textile article has been loaded to the gripping devices <NUM>, the gripping devices <NUM> are moved away from each other so as to straighten the textile article. At the same time, the textile articles are displaced with respect to the base parts <NUM> until an edge of the textile article is detected. Thereafter, the textile article is displaced with respect to the base part <NUM> along the detected edge until a predefined point at the textile article has been reached.

As the gripping devices <NUM> are mounted to robot arms <NUM>, complex movements are possible which allow the manipulators to follow complex contours and edges of the textile article.

Stated generally, the machine according to the invention can be considered as a linear positioning device for spreading and placing limp materials by using two actively controlled manipulators and sensors to firstly reach a straight boundary segment of the textile article and then perform linear edge tracing while stopping upon corner recognition.

Claim 1:
A machine (<NUM>) for handling limp material (<NUM>), in particular textile articles, the machine (<NUM>) comprising at least a first and a second gripping device (<NUM>) adapted for gripping the same piece of limp material (<NUM>) at the same time, at least one of the gripping devices (<NUM>) being connected to a drive system (<NUM>) adapted for displacing the gripping devices (<NUM>) with respect to each other, one of the gripping devices (<NUM>) being a manipulator (<NUM>) having a displacement mechanism (<NUM>) adapted for actively displacing the limp material (<NUM>) in a direction which is generally within a plane in which the limp material (<NUM>) is held in the manipulator (<NUM>), the machine (<NUM>) further comprising at least one sensor (<NUM>) adapted for detecting the limp material (<NUM>) and/or regions of interest, wherein the manipulator (<NUM>) comprises a base part (<NUM>) and a pressing part (<NUM>) which are displaceable with respect to each other, the displacement mechanism (<NUM>) being provided at the base part (<NUM>), the displacement mechanism (<NUM>) comprises at least one displacement wheel (<NUM>) which is arranged so as to engage at the limp material (<NUM>), characterized in that a receiving space (<NUM>) is provided between the base part (<NUM>) and the pressing part (<NUM>), the receiving space (<NUM>) being adapted for receiving an edge portion (E) of the limp material (<NUM>), the sensor (<NUM>) being arranged so as to detect the position of the edge portion (E) within the receiving space (<NUM>).