EP0240040A2 - Apparatus for picking-up flexible sheets, especially textiles - Google Patents

Abstract

The invention relates to a device for gripping layers of flexible material, of the type comprising a head (14) provided with a bearing surface, an openwork part (16) formed in said surface, a needle (103) movable relative at the head, a fine groove (15) formed in the head and means for kinematically guiding the needle in the plane of the groove (15). According to the present invention, the bearing surface and provided with a recess (102) and has a recessed area (100) and a projecting area (101). Two support lugs (110, 111) are preferably located on either side of the groove (15) at the level of the recessed area. These provisions improve the surface attachment conditions of the upper layer of flexible material to be gripped and eliminate the risk of seizure of the layer below.

Description

The invention relates to an improved device for gripping textile, knitted, woven or other layers. It relates to a device of the type described in patent FR 84.04804 or in the corresponding US patent 4,635,918, registered in the names of the applicants.

These patents describe a gripping device which makes it possible to grasp the upper layer of a stack, to the exclusion of any other, so as to peel it from the lower layers in order to transfer it. This device makes it possible, at the same time, on the one hand to ensure a firm grip of said upper layer, in order to prevent it from coming off during transfer, on the other hand to guarantee the detachment of this layer at term of transfer at the time of filing.

To this end, the targeted device comprises a bearing surface, and a needle movable relative to the latter: this needle cooperates with an openwork part and with a fine groove which the bearing surface comprises, in order to produce, in a first, a fold of the layer to be grabbed, then push this fold towards the openwork part and pinch or prick it at the end of movement.

The present invention proposes to improve the device to further reduce the risks of gripping several layers, even in the case of very thin layers (a few tenths of a millimeter).

It should be noted that this reliability of inputting a single layer is essential in practice to allow the device to be integrated into an automated process.

The device targeted by the invention comprises as basic means:
. at least one head with a bearing surface,
. an openwork part formed in said bearing surface,
. a needle associated with the head and mobile relative to the latter from an initial position where the end of the needle is located on one side of the perforated part,
. a fine groove made in the head so as to have a thickness greater than that of the needle in order to be able to contain it, said groove cutting the perforated part,
. and means for kinematically guiding the needle relative to the head, capable of guiding the end of the needle on a trajectory, situated in the plane of the groove and directed at least in its final portion towards the surface of support.

According to the present invention, the bearing surface is provided with a recess and has, on the side of the needle, an area, known as the recessed area, located slightly behind the opposite area, called the projecting area, in order to ensure different pressures on the layer of flexible material at the two zones.

Thus, the tissue undergoes less pressure in its portion called to form the fold and, thus released in this portion, lends itself better to the formation of this fold. This is formed with greater safety, the friction force required on the part of the needle, then becoming very low.

In addition, according to another characteristic of the invention, the bearing surface is provided in its recessed area with at least two bearing pins located on either side of the aforementioned groove. Preferably, each lug protrudes relative to the recessed area over a thickness substantially equal to the depth of the abovementioned recess.

These lugs improve the maintenance and guiding of the flexible layers, while preserving the freedom of movement or deformation of the upper layer at the level of the recessed area. Experiments have shown that these pins further reduce the risk of gripping the bottom layer, by ensuring a complementary blocking of the latter preventing this lower layer from wrinkling. In particular, such a device is extremely effective in the case of non-homogeneous stacking where the layers adhere in pairs to each other; in this case, the lower layer of a pair has a strong tendency to follow the movement of the top layer: despite this tendency, the device of the invention is able to grasp only the latter.

According to a preferred embodiment, in particular in the case of very thin layers, the needle is shaped to present at its end two separate tips and a retainer (formed by the part located between the bases of said tips). These points are preferably profiled in a bevel so as to form, in their part called to come into abutment with the fabric, an acute angle capable of hanging the fabric superficially, in order to constitute the fold by pushing the fabric towards the perforated part of the bearing surface.

In addition, according to another characteristic of the invention, the needle is a curved concavity needle oriented towards the bearing surface, and its kinematic guide means are adapted to impose on said needle an initial position such that its end makes projecting from the area set back from the bearing surface and the tangent at said end makes a slight angle relative to the plane of said area.

As will be understood more clearly below, this characteristic is combined with the other characteristics of the invention (release of the tissue at the level of the recessed area; stopping needle, etc.), to guarantee the formation of a fold in the layer. upper fabric, by means of a superficial attachment of said layer, eliminating any risk of simultaneous attachment of the lower layer. Thus, on the one hand, the guarantee of a fold in the upper layer leads to a certainty of grasping this layer at the end of movement of the needle, on the other hand, the way in which this fold is produced by hooking superficial, ensures that only this upper layer will be captured.

According to another characteristic of the invention, the means for kinematically guiding the needle are arranged to give the latter a capacity for movement towards the bearing surface: elastic means are then associated with said needle to urge it in the direction of its spacing relative to the head, towards an extreme stop position. In its initial stop position, the end of the needle projects slightly beyond the level of the projecting area of the bearing surface, so that said end is initially pushed back by the upper layer of flexible material and comes in elastic support against it. This arrangement further improves the surface attachment conditions of the upper layer, and makes it possible to obtain a device of remarkable reliability: secure grip of the top layer, strict elimination of the risks of grip of the bottom layer.

• - la figure 1 est une vue partielle en perspective de ce mode de réalisation, à échelle dilatée,
• - la figure 2 en est une coupe partielle par un plan vertical axial, montrant l'aiguille dans sa position initiale,
• - la figure 3 est une vue de détail en perspective de l'extrémité de l'aiguille,
• - la figure 4 est une coupe partielle du dispositif montrant l'aiguille en fin de mouvement,
• - les figures 5a, 5b, 5c et 6 sont des schémas explicatifs du fonctionnement du dispositif.

Other characteristics, objects and advantages of the invention will emerge from the description which follows with reference to the appended drawings, which present by way of nonlimiting example a preferred embodiment; on these drawings which form an integral part of this description:

• FIG. 1 is a partial perspective view of this embodiment, on an expanded scale,
• FIG. 2 is a partial section thereof through an axial vertical plane, showing the needle in its initial position,
• FIG. 3 is a detailed perspective view of the end of the needle,
• FIG. 4 is a partial section of the device showing the needle at the end of movement,
• - Figures 5a, 5b, 5c and 6 are explanatory diagrams of the operation of the device.

The gripping device shown by way of example in the figures comprises a gripping assembly secured to a vertical plate 6 carried by a chassis equipped with air blowing means (not shown); this chassis, these blowing means and the fixing of the plate to the chassis are similar to those described in the patents FR 84.04804 or US 4,635,918 already mentioned and will not be described again.

The plate 6 supports the body of a double-acting pneumatic cylinder 12 whose movable rod 12b is directed downwards in a substantially vertical position. As in the main application, this jack 12 is associated with a proximity sensor (not visible).

In the lower part, a gripping head 14 is screwed onto the end of the rod 12b of the jack, so as to be able to move in a vertical translational movement (as in the main application, guide means prevent the head from rotating on itself and guide it in translation).

This head is formed by a cylinder portion, the lower base of which is intended to act as a bearing surface for the tissue to be grasped. This circular base comprises a step from a few tenths of a millimeter to a few millimeters and consists of two flat zones, one 100 set back from the other 101. In the example, these two zones are separated by a rectilinear shoulder 102, the depth of which may in particular be between 0.2 and 1 mm depending on the thickness of the layers to be gripped. A depth of 0.4 mm is ideal for very thin layers a few tenths of a millimeter thick.

The head 14 is split with a thin blind groove 15 of thickness slightly greater than that of the needle described below. This groove extends in a vertical plane substantially perpendicular to the zones 100 and 101 and opens out along a diameter perpendicular to the shoulder 102.

In addition, the head 14 has an openwork part 16, in the example of circular section, which opens onto the recessed surface 100, in the center of the head. This perforated part 16 extends on either side of the plane containing the groove 15 which cuts it diametrically. The shoulder 102 passes near said perforated part, the projecting area 101 extending on one side thereof, the recessed area extending towards the other side; in the example, the shoulder 102 is approximately tangent to the perforated part 16.

In addition, the bearing surface is provided in its recessed area 100 with two bearing pins 110 and 111, located on either side of the groove 15, on the edge of said recessed area. In the example, these pins are carried by a guide plate 25 fixed at the edge of the head. These support lugs, located on each side of the base of the plate 25, are dimensioned to project up to level N of the projecting zone 101.

Furthermore, the plate 6 carries means for kinematically guiding a needle 103. These means consist of members similar to those described in the main application: support 17 secured to the plate 6 in a position transversely offset with respect to the head , hinge pin 20 carried by the support 17 around which a link 21 can pivot, elastic means 22 urging the link (and therefore the needle) in the direction of its spacing relative to the head, pressure screw 24 for fixing of the needle 103 by its heel.

These means are arranged so that the needle is located in the plane of the groove 15 and can move in this plane relative to the head, by rotation of the link 21 around its axis 20.

The needle 103 is a curved needle whose concavity is oriented towards the bearing surface of the head. It passes through a light 112 formed in the guide plate 25 already mentioned, which is fixed at the edge of the head. This light has a dimension much greater than that of the needle so as to leave the latter with a faculty of movement towards the bearing surface, the elastic means 22 tending to press the needle against the lower edge of said light. (which defines the extreme stop position).

As illustrated in Figures 1, 2 and 3, the needle is shaped to have at its end two separate tips 104 and 105 and a stopper 106; the latter is formed by the part located between the bases of said points. These points can protrude by approximately 3/10 to 6/10 mm from the retainer.

Each point has a beveled front edge such as 107, oriented so that the angular part 108 of said edge (part located opposite the bearing surface, called to come first into contact with the fabric) forms an acute angle β, in particular of the order of 60 to 80 °, and is projecting at the front relative to the other angular part 109 (located opposite the bearing surface).

In addition, the kinematic guide means (light of the wafer 25, link 21, support 17) are arranged to impose on the needle an initial position as shown diagrammatically in FIG. 2. The end of the latter protrudes by relative to the recessed area 100, but also relative to the level N of the area 101; in this initial position, the needle end is located in the vicinity of the perforated part 16. The overflow -S- of the needle relative to the level N can be of the order of a few tenths of a millimeter.

In addition, in its initial position, when the needle is not pushed back, the tangent at its end forms a small angle α with respect to a plane parallel to the bearing surface. This angle can be of the order of a few degrees (up to 20 to 30 °). Thus, the needle comes into contact almost tangentially with the upper layer of fabric when the bearing surface is arranged against a stack of layers.

In addition, the needle is guided so that, during its movement, it crosses the perforated part 16 to come at the end of movement in a final position as shown in FIG. 4. The trajectory has been shown diagrammatically in this figure. T of the needle end assuming that the needle was not repelled by a layer of fabric.

In the final portion of the path T, the two end points 104 and 105 engage in the groove 15 (half of the groove opposite the half by which the needle arrives). In this position, the stopper 106 which is located at the base of the points is located approximately at the intersection between the groove and the perforated part.

At the end of the movement, the needle is thus able to pinch the fold of the tissue, which was formed in the first part of the movement.

Figures 5a, 5b and 5c illustrate the operation of the device.

In the first phase (Figure 5a), the head 14 is in the low position and the jack 12 which carries it is in the open air. The stack, the upper layer of which is symbolized in C, comes into contact with the bearing surface. The parity C₁ of the upper layer, which is located in abutment with the projecting zone 101, is blocked by the latter, while the part C₂, located opposite the recessed zone 100, retains a certain freedom. The lugs 110 and 111 form a complementary support which, without eliminating this freedom, ensures that the stack is maintained, preventing the bottom layer from tending to follow the deformations or displacements of the upper layer, even if significant adhesion binds the two layers. FIG. 6 shows a detail of the head, seen from the side of the plate 25.

The needle 103 rests against the part C₂ of the upper layer and is slightly repelled by the latter: this produces an elastic support, of low penetration angle.

The relative approximation between the stack and the head (FIG. 5b) generates a retraction of the head upwards and a movement of the needle towards the head and towards the perforated part 16 thereof: the angular parts 108 of the end of needle hook the top layer of fabric. The stopper 106 located between the points limits the penetration thereof. The elasticity of the support (provided by the elastic means 22) contributes to guaranteeing a surface attachment. The upper layer, blocked by the zone 101, folds as shown in FIG. 5b, forming an inverted V-shaped fold which is housed in the perforated part 16.

At the end of the head / stacking approach, the needle arrives in a position as shown diagrammatically in FIG. 5c. It pinches the fold of the fabric at the intersection of the groove and the openwork part. Only the short points protruding from the retainer penetrate the fabric.

In this position, the proximity sensor controls the pneumatic supply of the jack 12 which locks the head in the high position. The firmly held fabric layer is thus locked and cannot come off.

The stack is then separated from the head and the operations of transferring and then depositing the captured layer can be carried out.

Claims (14)

1 / - Device for gripping layers of flexible material, comprising at least one head (14) provided with a bearing surface, an openwork part (16) formed in said bearing surface, a needle (103) associated with the head and movable relative to the latter from an initial position where the end of the needle is located on one side of the perforated part, a fine groove (15) formed in the head so as to have a thickness greater than that of the needle and to cut the perforated part of the head, and kinematic guide means of the needle (103) relative to the head (14), capable of guiding the end of the needle on a trajectory located in the plane of the groove (15) and directed at least in its final position towards the bearing surface, said device being characterized in that the bearing surface is provided with a recess (102) and has, side of the needle, a zone, known as the recessed zone (100), situated slightly behind the opposite zone, di te protruding area (101), in order to ensure at the two areas of different pressures on the layer of flexible material. 2 / - Gripping device according to claim 1, characterized in that the bearing surface is provided in its recessed area (100) with at least two bearing pins located on either side of the groove ( 15). 3 / - Gripping device according to one of claims 1 or 2, characterized in that the recess (102) of the support surface passes close to the perforated part (16) so that the recessed areas (100 ) and projecting zone (101) extend one towards one side of this perforated part, the other towards the other side. 4 / - Gripping device according to one of claims 1, 2 or 3, characterized in that the recess (102) of the bearing surface extends substantially along a straight line perpendicular to the plane of the groove (15). 5 / - Gripping device according to claims 3 and 4 taken together, in which the perforated part (16) is located substantially in the center of the surface support, the groove (15) being formed so as to cut diametrically said perforated part, said device being characterized in that the recess between the recessed area (100) and the projecting area (101) of the surface of support forms a shoulder (102) perpendicular to the plane of the groove (15) and approximately tangent to the perforated part (16), which opens onto the recessed area (100). 6 / - Gripping device according to one of claims 1, 2, 3, 4 or 5, characterized in that the recessed area (100) and the projecting area (101) are flat, the recess (102) between these zones having a depth approximately between 0.2 and 1 mm. 7 / - Gripping device according to claim 2, characterized in that each support lug protrudes relative to the recessed area over a thickness substantially equal to the depth of the recess (102). 8 / - gripping device according to one of claims 1, 2, 3, 4, 5, 6 or 7, wherein the needle (103) is shaped to have at its end two separate points (104, 105) and a retainer (106) formed by the part located between the bases of said points. 9 / - Gripping device according to claim 8, characterized in that each needle point (104, 105) has a bevelled front edge (107) oriented so that the angular part (108) of said edge, located at the opposite of the support surface, forms an acute angle (β) and is projecting at the front relative to the other angular part (109) (located opposite the support surface). 10 / - Gripping device according to claim 9, characterized in that the kinematic guide means are adapted so that, in the final portion of its trajectory, the needle (103) passes through the perforated part (16), its two end points (104, 105) engaging in the groove (15), so that the retainer (106) located at the base of said points is approximately positioned at the intersection between said groove and said perforated part. 11 / - Gripping device according to one of the preceding claims in which the needle (103) is a curved concavity needle oriented towards the bearing surface, characterized in that the kinematic guide means are arranged to impose on the needle an initial position such that the end of the latter protrudes relative to the recessed area (100) of the bearing surface, in the vicinity of the perforated part (16), and that the tangent at said end makes a slight angle (α) relative to a plane parallel to the bearing surface. 12 / - Gripping device according to claim 11, wherein the kinematic guide means are arranged to leave the needle (103) a faculty of movement towards the bearing surface, elastic means (22) being associated with said needle to urge it in the direction of its spacing relative to the head (14) towards an extreme stop position, characterized in that, in its initial stop position, the end of the needle (103) projects slightly relative to the level of the projecting zone (101) of the bearing surface, so that said end is initially pushed back by the upper layer of flexible material and comes into elastic abutment thereon. 13 / - Gripping device according to one of the preceding claims, in which the means for kinematically guiding the needle comprise:
. an articulated link (21), adapted to carry the needle (103),
. an axis (20) of articulation of said link, carried by a support (17),
. means (12) for guiding in translation, adapted to allow relative movement of translation between the support (17) and the head (14),
. a guide plate (25), secured to the head (14) and comprising a lumen (112) through which the needle (103) passes. 14 / - Gripping device according to claims 2 and 13 taken together, characterized in that the support pins are carried by the guide plate (25) and located on each side of the base thereof.

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