CA2201059A1 - Robot gripper for fixturing a three-dimensional object - Google Patents
Robot gripper for fixturing a three-dimensional objectInfo
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- CA2201059A1 CA2201059A1 CA 2201059 CA2201059A CA2201059A1 CA 2201059 A1 CA2201059 A1 CA 2201059A1 CA 2201059 CA2201059 CA 2201059 CA 2201059 A CA2201059 A CA 2201059A CA 2201059 A1 CA2201059 A1 CA 2201059A1
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- fingers
- sheet
- gripper
- another
- groove
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Abstract
A robotic gripper for fixturing and manipulating a sheet of substantially rigid material e.g. a sheet metal part has three fingers with circumferential grooves thereon. The sheet metal part has at least one opening of a size suited to accommodate one of the fingers.
The other fingers can engage the edges of other openings in the sheet metal part or the outside edge of the part. The fingers can be moved away from each other or towards each other respectively depending on the positioning of the fingers, whereby the sheet metal part is fixtured by means of the grooves of the fingers.
The other fingers can engage the edges of other openings in the sheet metal part or the outside edge of the part. The fingers can be moved away from each other or towards each other respectively depending on the positioning of the fingers, whereby the sheet metal part is fixtured by means of the grooves of the fingers.
Description
2 2 0 i ~ 5 ~ Doc. No. 14-3 CA
.
Robot Gripper for Fixturing a Three-Dimensional Object Field of the Invention s This invention relates generally to robotic grippers and more particularly to a gripper and method of gripping a sheet material.
Background of the Invention 0 Many gripping means are known to be used with various tools or for gripping, holding and moving objects, and particularly as a ter1ninal organ of a manipulator or programmed robot. Most often, these grippers make broad surface contact with the objects to be gripped. Alternatively, smaller pads on fingers are used and an object is held by forcing the fingers and pads in an inward direction against the outer surface of the object.
In some instances grippers are provided with two fingers which do the gripping either while parallel to one another, or while pivoting about two shafts affixed to a base piece. These two fingers generally termin~te in planar, in some cases resilient, contact surfaces, pe~ ing ordinary objects to be held immobile by making broad surface or 20 linear contact on each surface.
United States Patent number 4,653,793 in the name of Guinot et al. describes a gripper having a plurality of contact pads providing a point contact with an object to be gripped. In operation, when an object is to be gripped the pads apply an inward force on 25 the outside surface of the object.
Another robotic gripper is described in United States Patent number 5,178,431 inthe name of Voellmer, the gripper including a pair of fingers movable toward and away from one another while the fingers remain parallel to each other.
2 2 0 l O J 9 Doc. No. 14-3 CA
O' Although these grippers may adequately provide their intçnded function, there is a need for a programmable gripper for accurately fixturing three-dimensional sheet metal parts of various shapes.
S For example, in the automotive and aircraft industry, sheet metal parts must be fixtured during the assembly of vehicle bodies. Furthermore, it is ~l~r~ d to have a single gripper that can easily be programmed to f1xture parts having a plurality of different shapes and sizes.
lo It is therefore an object of this invention to provide a multi-degree-of-freedom gripper for use in robotic fixtureless assembly.
It is a further object of this invention to provide a gripper for fixturing a plurality of different sheet metal parts by only ch~nging computer controlled axes.
Summaly of the Invention In accordance with the invention, a gripper is provided having a plurality of movable fingers sized to fit within openings or slots within a rigid or semi-rigid sheet material such as a metal sheet part. The fingers preferably all have guide means, for example in the form of grooves or knurling to engage the periphery of one of the slots or the edge of the sheet in a manner to prevent a slippage or movement of the sheet along the length of the fmger. As the fingers are moved toward one another or away from one another, they are stopped by the inward or outward facing slot walls or by the edge of the sheet.
In accordance with the invention, there is further provided, a gripper for holding a sheet of material defining an outside edge, said gripper comprising:
at least three fingers each being relatively movable in at least one of a first direction , ~2 ~ ~ a~ Doc.No. 14-3CA
toward another and a second direction away from another, said fingers having fixing no-clamp means for eng~Eing said outside edge of said sheet and preventing said sheet from substantially slipping or moving relative to the fingers when said fingers are moved as far as possible in one of the first direction and the second direction; and, 5 drive means for relatively moving said fingers in at least one o~ said first and second directions.
Advantageously, the invention is capable of fixturing sheet metal parts that have existing holes or slots defined therein; the invention relies on using these existing holes lo and/or edges of the parts and due to this, it is capable of fixturing small non-uniform surfaces. Furthermore, the invention is suited to fixturing extremely thin parts that might otherwise be crushed by an inward force applied to edges of the part. By relying on slots within the sheet, fingers can be moved away from each other once placed within respective slots in an outward direction essentially applying a stretching force on a thin 5 part rather than compressing and collapsing it.
Since friction is not used in the fixturing of parts, oily objects that are difficult to pick up with conventional parallel jaw or vacuum cup grippers can be easily manipulated and fixtured.
The invention further lends itself to fixturing parts accurately even when theirinitial placement is inaccurate.
Brief Description of the Dl ~WiLgS
Exemplary embodiments of the invention will now be described in conjunction with the drawings in which:
Figs. la and lb are top and side views respectively of a sheet metal part having a gripper finger located within a slot of the metal part wherein two other fingers are disposed about the periphery of the part shown in a non-fixtured position;
~ ~ 2 0 ~ o ~ q Doc. No. 14-3 CA
Figs 1 c and 1 d are top and side views respectively of the sheet metal part shown in Figs 1 a and 1 b, having a gripper finger located within a slot of the metal part wherein two other fingers are disposed at the periphery of the part shown in a fixtured position;
Fig 2a is a side view taken partly in cross section through the line A-A of the sheet metal part shown in Fig. 2b;
Fig. 2b is a top view of a sheet metal part having gripper fingers located within o three slots of the sheet metal part shown in a non-fixtured position, Figs 2c and 2d are side and top views of the sheet metal part shown in Figs 2a and 2b, wherein the fingers are at outer ends of the slots of the sheet metal part in a fixtured position;
Figs 3a to 3g are plan views of sheets of metal shown in a pluralit~ of fixtured positions;
Fig. 4 is a perspective view of a robotic gripper in accordance with the invention 20 having two fixed fingers and one movable finger;
Fig. 5 is a perspective view of a robotic gripper in accordance with the invention having two movable fingers and one fixed finger;
2s Fig. 6 is a perspective view of another embodiment of a robotic gripper having 3 movable ~mgers and one fixed finger, in accordance with the invention; and Fig. 7 is a pictorial view of the gripper shown in Fig. 4 mounted on industrial robot arm.
~ . 22 0 1 ~ ~ Doc.No. 14-3CA
Detailed Description of the Invention An exemplary gripper of the invention is a mechanical device comprising three fingers 1 Oa, 1 Ob, and 1 Oc, intended to be attached to the end of an arm 17 of an industrial 5 robot as shown in Fig. 7. A sheet of material 14 may be a thick or thin sheet of rigid or non-rigid material, for example, a thick or thin metal sheet, or alternatively a sheet of plastic. The sheet material may be planar or of a more complex shape such as a molded autobody part such as a car door.
o Referring now to Fig. la and lb, a workpiece in the form of a sheet of steel 14 is shown in an ~]n~xtllred position. Three fingers attached to and controlled by actuating means (similar to those shown in Fig. 6) are positioned about the workpiece 14 such that one finger is placed within an opening in the form of a slot 16 and the other fingers are disposed about outside edges of the workpiece 14. In this configuration, the fingers are ready to be moved toward one another. This can be accomplished by several methods.
For example, the one finger disposed within the slot 16 can be moved toward the other two fingers, which may be fixed and non-movable. Alternatively, only two fingers may be movable (shown in Fig. 5) or all three fingers may be movable and moved in toward one another (as shown in Fig. 6).
As can be seen in Figs lb and 1 d, the fingers are equipped with means for preventing the workpiece during fixtllring and when fixtured from moving or slipping, in the form of guide means or tracking meansl2. In a preferred embodiment these means 12 are in the form of circumferential V-grooves around the periphery of each finger.
However a circumferential groove may also be provided around the periphery of a finger that has a somewhat square cross section, thus the term circumferential need not be limited to following a circular path.
Alternatively, the means 12 may be embodied by knurling or equivalent means.
~ ~ 2 0 1 0 5 ~ Doc. No. 14-3 CA
In Figs. 1 c and 1 d, the fingers are shown in an inwardmost position wherein the fingers have been moved relatively toward one another until the grooves all tightly accommodate edges of the sheet of material. 13y providing a slot or opening that is substantially larger than the cross section of a finger, more tolerance is allowed for in s aligning and placing the finger within the slot. By the same token, providing a groove 12 that is larger than the thickness of the sheet m~teri~l allows an object to be located and grasped allowing for further robot error. The groove should be sized to accommodate a range of customary sheet thicknesses.
o Figs. 2a and 2b illustrate three fingers 1 Oa, lOb, and 1 Oc which are placed within slots 1 6a, 1 6b, and 16c of a workpiece 14. After the fingers are located within the slots they are guided along the slot walls by having their grooves 12 track along the slot walls to an end position as shown in Figs. 2c and 2d, wherein the fingers have been moved apart until their movement is limited by slot walls or edges.
As is apparent from Figs 2d and lc, or viewing Figs. 3c to 3g, a workpiece may be fixtured by placing fingers into respective adjacent slots and bringing the fingers together in an inward direction as far as possible or alternatively by bringing the fingers apart as far as possible while m~int~ining the fingers within the slots. Advantageously, by bringing the fingers apart while in the slots allows a thin sheet m~t~ri~l such as a plastic film to be fixtured without it collapsing as it would if an inward force was brought to bear on the sheet.
The provision of a V-shaped groove conveniently allows a range of thicknesses of materials to be fixtured.
Turning now to Figs 3a to 3g, the programmable gripper comprising 3 fingers 1 Oa, 1 Ob, and 1 Oc as described heretofore, is shown as being capable of fixturing a plurality of dirr~lel~ configurations. Since the fingers and the grooves thereon are sized to receive a plurality of thicknesses of sheet material, and since the openings or slots can be ~ 2 2 0 1 0 ~ q Doc. No. 14-3 CA
of a variety of shapes and sizes, a change in the program controlling the robot's fingers is all that is necessary in conforming to a different workpiece. For example, the robot must know the approximate location of the workpiece and have some information relating to the shape and location of the slots.
s Fig. 4 shows an embodiment of the invention wherein only one finger 1 Oc of the 3 provided is actually movable. Although two fingers are fixed lOa and lOb, a variety of shapes and sizes of materials can be fixtured using this arrangement. Fig. 5 shows an embodiment of the invention wherein 2 of the 3 fingers, lOb and lOc, are actually 10 movable. In both of the embodiments shown in Figs 4 and 5 at least two fingers are capable of being relatively moved toward or away from at least one finger.
In contrast, a more complex arrangement is shown in Fig. 6, wherein the gripper can move each finger with 3 degrees of mobility (x, y, and z) thereby providing 9 15 degrees of mobility. Each of the 9 cylinders 60 shown are linear actuators. Although this arrangement is more complex and costly, it is capable of picking up and fixturing a greater variety of shapes.
It will be understood that the embodiments described and illuskated above are 20 merely exemplary. It is possible and may indeed be advisable or even necessary to provide a gripper with more than three fingers if the m:~tt?ri~l, as mentioned hereinabove, is relatively thin or flimsy and needs to be stretched at more than three spots. Further, the definition "relatively movable" is used herein to differentiate from actual movement and to define an arrangement as illustrated e.g. in Fig. ~ or 5 where only one or two fingers 2s are actually movable relative to the base but the movement changes the distance between the fixed and the movable fingers.
It will also be appreciated that the definition of a "finger" is not limiting to a specific shape nor length, as long as the finger is dimensioned to fit into a slot, opening or 30 hole in the material to be fixtured, and as long as the finger has a sheet-fixing means --~, 2 2 0 1 0 ~) ~ Doc. No. 14-3 CA
thereon. The fixing means for eng~ging the sheet need not be disposed at the end of the finger. It will be noted that for the purpose of the invention, it is only the part of the finger with the groove thereon that is of importance in locating and fixturing the sheet.
Accordingly, if one of the fingers is moved in a direction "z" as shown in Fig. 2a and 2b, 5 the sheet 14 will be displaced and the relative distance between the grooves 1 Oa, 1 Ob and 1 Oc will change although this will not show in the plan view of Fig. 2b. Still, this will satisfy the definition of relative movement of the fingers as used throughout the specification.
lo It will also be appreciated that the fingers may be disposed and moved (or relatively moved) not only in a parallel arrangement as illustrated (i.e. with their longitudinal axes parallel at all times) but at an angle relative to each other, for instance to accommodate a curvature of the material. The definition "movable" is intended to encompass such embodiments.
It is a feature and an advantage of the invention that the sheet of material may be held and immobilized in a predetermined position without clamping the surface of the sheet or imparting a sheet-bending force transversely to its surface.
Of course, numerous other embo(liments may be envisaged, without departing from the spirit and scope of the invention.
The invention can also be applied to a sheet which has no openings. The at leastthree fingers are positioned to engage the outside edge of the sheet and moved towards each other thus gripping the sheet. This assumes, of course, that the sheet has a sufficient rigidity.
.
Robot Gripper for Fixturing a Three-Dimensional Object Field of the Invention s This invention relates generally to robotic grippers and more particularly to a gripper and method of gripping a sheet material.
Background of the Invention 0 Many gripping means are known to be used with various tools or for gripping, holding and moving objects, and particularly as a ter1ninal organ of a manipulator or programmed robot. Most often, these grippers make broad surface contact with the objects to be gripped. Alternatively, smaller pads on fingers are used and an object is held by forcing the fingers and pads in an inward direction against the outer surface of the object.
In some instances grippers are provided with two fingers which do the gripping either while parallel to one another, or while pivoting about two shafts affixed to a base piece. These two fingers generally termin~te in planar, in some cases resilient, contact surfaces, pe~ ing ordinary objects to be held immobile by making broad surface or 20 linear contact on each surface.
United States Patent number 4,653,793 in the name of Guinot et al. describes a gripper having a plurality of contact pads providing a point contact with an object to be gripped. In operation, when an object is to be gripped the pads apply an inward force on 25 the outside surface of the object.
Another robotic gripper is described in United States Patent number 5,178,431 inthe name of Voellmer, the gripper including a pair of fingers movable toward and away from one another while the fingers remain parallel to each other.
2 2 0 l O J 9 Doc. No. 14-3 CA
O' Although these grippers may adequately provide their intçnded function, there is a need for a programmable gripper for accurately fixturing three-dimensional sheet metal parts of various shapes.
S For example, in the automotive and aircraft industry, sheet metal parts must be fixtured during the assembly of vehicle bodies. Furthermore, it is ~l~r~ d to have a single gripper that can easily be programmed to f1xture parts having a plurality of different shapes and sizes.
lo It is therefore an object of this invention to provide a multi-degree-of-freedom gripper for use in robotic fixtureless assembly.
It is a further object of this invention to provide a gripper for fixturing a plurality of different sheet metal parts by only ch~nging computer controlled axes.
Summaly of the Invention In accordance with the invention, a gripper is provided having a plurality of movable fingers sized to fit within openings or slots within a rigid or semi-rigid sheet material such as a metal sheet part. The fingers preferably all have guide means, for example in the form of grooves or knurling to engage the periphery of one of the slots or the edge of the sheet in a manner to prevent a slippage or movement of the sheet along the length of the fmger. As the fingers are moved toward one another or away from one another, they are stopped by the inward or outward facing slot walls or by the edge of the sheet.
In accordance with the invention, there is further provided, a gripper for holding a sheet of material defining an outside edge, said gripper comprising:
at least three fingers each being relatively movable in at least one of a first direction , ~2 ~ ~ a~ Doc.No. 14-3CA
toward another and a second direction away from another, said fingers having fixing no-clamp means for eng~Eing said outside edge of said sheet and preventing said sheet from substantially slipping or moving relative to the fingers when said fingers are moved as far as possible in one of the first direction and the second direction; and, 5 drive means for relatively moving said fingers in at least one o~ said first and second directions.
Advantageously, the invention is capable of fixturing sheet metal parts that have existing holes or slots defined therein; the invention relies on using these existing holes lo and/or edges of the parts and due to this, it is capable of fixturing small non-uniform surfaces. Furthermore, the invention is suited to fixturing extremely thin parts that might otherwise be crushed by an inward force applied to edges of the part. By relying on slots within the sheet, fingers can be moved away from each other once placed within respective slots in an outward direction essentially applying a stretching force on a thin 5 part rather than compressing and collapsing it.
Since friction is not used in the fixturing of parts, oily objects that are difficult to pick up with conventional parallel jaw or vacuum cup grippers can be easily manipulated and fixtured.
The invention further lends itself to fixturing parts accurately even when theirinitial placement is inaccurate.
Brief Description of the Dl ~WiLgS
Exemplary embodiments of the invention will now be described in conjunction with the drawings in which:
Figs. la and lb are top and side views respectively of a sheet metal part having a gripper finger located within a slot of the metal part wherein two other fingers are disposed about the periphery of the part shown in a non-fixtured position;
~ ~ 2 0 ~ o ~ q Doc. No. 14-3 CA
Figs 1 c and 1 d are top and side views respectively of the sheet metal part shown in Figs 1 a and 1 b, having a gripper finger located within a slot of the metal part wherein two other fingers are disposed at the periphery of the part shown in a fixtured position;
Fig 2a is a side view taken partly in cross section through the line A-A of the sheet metal part shown in Fig. 2b;
Fig. 2b is a top view of a sheet metal part having gripper fingers located within o three slots of the sheet metal part shown in a non-fixtured position, Figs 2c and 2d are side and top views of the sheet metal part shown in Figs 2a and 2b, wherein the fingers are at outer ends of the slots of the sheet metal part in a fixtured position;
Figs 3a to 3g are plan views of sheets of metal shown in a pluralit~ of fixtured positions;
Fig. 4 is a perspective view of a robotic gripper in accordance with the invention 20 having two fixed fingers and one movable finger;
Fig. 5 is a perspective view of a robotic gripper in accordance with the invention having two movable fingers and one fixed finger;
2s Fig. 6 is a perspective view of another embodiment of a robotic gripper having 3 movable ~mgers and one fixed finger, in accordance with the invention; and Fig. 7 is a pictorial view of the gripper shown in Fig. 4 mounted on industrial robot arm.
~ . 22 0 1 ~ ~ Doc.No. 14-3CA
Detailed Description of the Invention An exemplary gripper of the invention is a mechanical device comprising three fingers 1 Oa, 1 Ob, and 1 Oc, intended to be attached to the end of an arm 17 of an industrial 5 robot as shown in Fig. 7. A sheet of material 14 may be a thick or thin sheet of rigid or non-rigid material, for example, a thick or thin metal sheet, or alternatively a sheet of plastic. The sheet material may be planar or of a more complex shape such as a molded autobody part such as a car door.
o Referring now to Fig. la and lb, a workpiece in the form of a sheet of steel 14 is shown in an ~]n~xtllred position. Three fingers attached to and controlled by actuating means (similar to those shown in Fig. 6) are positioned about the workpiece 14 such that one finger is placed within an opening in the form of a slot 16 and the other fingers are disposed about outside edges of the workpiece 14. In this configuration, the fingers are ready to be moved toward one another. This can be accomplished by several methods.
For example, the one finger disposed within the slot 16 can be moved toward the other two fingers, which may be fixed and non-movable. Alternatively, only two fingers may be movable (shown in Fig. 5) or all three fingers may be movable and moved in toward one another (as shown in Fig. 6).
As can be seen in Figs lb and 1 d, the fingers are equipped with means for preventing the workpiece during fixtllring and when fixtured from moving or slipping, in the form of guide means or tracking meansl2. In a preferred embodiment these means 12 are in the form of circumferential V-grooves around the periphery of each finger.
However a circumferential groove may also be provided around the periphery of a finger that has a somewhat square cross section, thus the term circumferential need not be limited to following a circular path.
Alternatively, the means 12 may be embodied by knurling or equivalent means.
~ ~ 2 0 1 0 5 ~ Doc. No. 14-3 CA
In Figs. 1 c and 1 d, the fingers are shown in an inwardmost position wherein the fingers have been moved relatively toward one another until the grooves all tightly accommodate edges of the sheet of material. 13y providing a slot or opening that is substantially larger than the cross section of a finger, more tolerance is allowed for in s aligning and placing the finger within the slot. By the same token, providing a groove 12 that is larger than the thickness of the sheet m~teri~l allows an object to be located and grasped allowing for further robot error. The groove should be sized to accommodate a range of customary sheet thicknesses.
o Figs. 2a and 2b illustrate three fingers 1 Oa, lOb, and 1 Oc which are placed within slots 1 6a, 1 6b, and 16c of a workpiece 14. After the fingers are located within the slots they are guided along the slot walls by having their grooves 12 track along the slot walls to an end position as shown in Figs. 2c and 2d, wherein the fingers have been moved apart until their movement is limited by slot walls or edges.
As is apparent from Figs 2d and lc, or viewing Figs. 3c to 3g, a workpiece may be fixtured by placing fingers into respective adjacent slots and bringing the fingers together in an inward direction as far as possible or alternatively by bringing the fingers apart as far as possible while m~int~ining the fingers within the slots. Advantageously, by bringing the fingers apart while in the slots allows a thin sheet m~t~ri~l such as a plastic film to be fixtured without it collapsing as it would if an inward force was brought to bear on the sheet.
The provision of a V-shaped groove conveniently allows a range of thicknesses of materials to be fixtured.
Turning now to Figs 3a to 3g, the programmable gripper comprising 3 fingers 1 Oa, 1 Ob, and 1 Oc as described heretofore, is shown as being capable of fixturing a plurality of dirr~lel~ configurations. Since the fingers and the grooves thereon are sized to receive a plurality of thicknesses of sheet material, and since the openings or slots can be ~ 2 2 0 1 0 ~ q Doc. No. 14-3 CA
of a variety of shapes and sizes, a change in the program controlling the robot's fingers is all that is necessary in conforming to a different workpiece. For example, the robot must know the approximate location of the workpiece and have some information relating to the shape and location of the slots.
s Fig. 4 shows an embodiment of the invention wherein only one finger 1 Oc of the 3 provided is actually movable. Although two fingers are fixed lOa and lOb, a variety of shapes and sizes of materials can be fixtured using this arrangement. Fig. 5 shows an embodiment of the invention wherein 2 of the 3 fingers, lOb and lOc, are actually 10 movable. In both of the embodiments shown in Figs 4 and 5 at least two fingers are capable of being relatively moved toward or away from at least one finger.
In contrast, a more complex arrangement is shown in Fig. 6, wherein the gripper can move each finger with 3 degrees of mobility (x, y, and z) thereby providing 9 15 degrees of mobility. Each of the 9 cylinders 60 shown are linear actuators. Although this arrangement is more complex and costly, it is capable of picking up and fixturing a greater variety of shapes.
It will be understood that the embodiments described and illuskated above are 20 merely exemplary. It is possible and may indeed be advisable or even necessary to provide a gripper with more than three fingers if the m:~tt?ri~l, as mentioned hereinabove, is relatively thin or flimsy and needs to be stretched at more than three spots. Further, the definition "relatively movable" is used herein to differentiate from actual movement and to define an arrangement as illustrated e.g. in Fig. ~ or 5 where only one or two fingers 2s are actually movable relative to the base but the movement changes the distance between the fixed and the movable fingers.
It will also be appreciated that the definition of a "finger" is not limiting to a specific shape nor length, as long as the finger is dimensioned to fit into a slot, opening or 30 hole in the material to be fixtured, and as long as the finger has a sheet-fixing means --~, 2 2 0 1 0 ~) ~ Doc. No. 14-3 CA
thereon. The fixing means for eng~ging the sheet need not be disposed at the end of the finger. It will be noted that for the purpose of the invention, it is only the part of the finger with the groove thereon that is of importance in locating and fixturing the sheet.
Accordingly, if one of the fingers is moved in a direction "z" as shown in Fig. 2a and 2b, 5 the sheet 14 will be displaced and the relative distance between the grooves 1 Oa, 1 Ob and 1 Oc will change although this will not show in the plan view of Fig. 2b. Still, this will satisfy the definition of relative movement of the fingers as used throughout the specification.
lo It will also be appreciated that the fingers may be disposed and moved (or relatively moved) not only in a parallel arrangement as illustrated (i.e. with their longitudinal axes parallel at all times) but at an angle relative to each other, for instance to accommodate a curvature of the material. The definition "movable" is intended to encompass such embodiments.
It is a feature and an advantage of the invention that the sheet of material may be held and immobilized in a predetermined position without clamping the surface of the sheet or imparting a sheet-bending force transversely to its surface.
Of course, numerous other embo(liments may be envisaged, without departing from the spirit and scope of the invention.
The invention can also be applied to a sheet which has no openings. The at leastthree fingers are positioned to engage the outside edge of the sheet and moved towards each other thus gripping the sheet. This assumes, of course, that the sheet has a sufficient rigidity.
Claims (16)
1. A gripper for holding a sheet of material defining an outside edge and having at least one opening therein, said gripper comprising:
at least three fingers each being relatively movable in at least one of a first direction toward another and a second direction away from another, at least one of said fingers being sized to fit within said at least one opening, said fingers having fixing no-clamp means for engaging said sheet and preventing said sheet from substantially slipping or moving relative to the fingers when at least one of said fingers is placed in said opening and said fingers are moved as far as possible in one of the first direction and the second direction; and, drive means for relatively moving said fingers in at least one of said first and second directions.
at least three fingers each being relatively movable in at least one of a first direction toward another and a second direction away from another, at least one of said fingers being sized to fit within said at least one opening, said fingers having fixing no-clamp means for engaging said sheet and preventing said sheet from substantially slipping or moving relative to the fingers when at least one of said fingers is placed in said opening and said fingers are moved as far as possible in one of the first direction and the second direction; and, drive means for relatively moving said fingers in at least one of said first and second directions.
2. The gripper as defined in claim 1, wherein the fixing means for preventing said sheet from slipping comprises means for tracking along an edge of said at least one opening as the fingers are relatively moved.
3. The gripper as defined in claim 1, wherein the fixing means for preventing a sheet from slipping comprises a groove on each of the fingers, said groove sized to receive said edge of the sheet.
4. The gripper as defined in claim 3, wherein at least one of the grooves is tapered to receive a range of edge thicknesses.
5. The gripper as defined in claim 2, wherein the means for tracking comprises acircumferential groove near the tip of one of the fingers.
6. The gripper as defined in claim 5, wherein the circumferential groove is a tapered V-groove.
7. The gripper as defined in claim 2 wherein the sheet is a substantially rigid sheet.
8. A gripper for holding a sheet of material having slots defined therein by walls of a thickness t, the gripper comprising:
at least three relatively movable grasping fingers, movable toward one another and/or away from one another, the fingers each being sized to fit within one of the slots and having a groove of a width of at least t for sliding along a respective slot wall and for preventing said sheet from slipping or moving relative to the fingers when the fingers are placed in the slots and moved as far apart as possible or as close to one another as possible within the slots; and, drive means for moving the fingers.
at least three relatively movable grasping fingers, movable toward one another and/or away from one another, the fingers each being sized to fit within one of the slots and having a groove of a width of at least t for sliding along a respective slot wall and for preventing said sheet from slipping or moving relative to the fingers when the fingers are placed in the slots and moved as far apart as possible or as close to one another as possible within the slots; and, drive means for moving the fingers.
9. A gripper for holding a sheet of material having openings defined therein, comprising:
at least three grasping fingers each being relatively movable in one of a first direction toward another and a second direction away from another, at least one of the fingers being sized to fit within one of the openings, each of the at least three fingers having means for preventing the sheet from substantially slipping or moving relative to the fingers when one of the fingers is placed in the openings and moved as far as possible in the first direction; and, drive means for moving the each of the fingers in at least one of the first and second directions.
at least three grasping fingers each being relatively movable in one of a first direction toward another and a second direction away from another, at least one of the fingers being sized to fit within one of the openings, each of the at least three fingers having means for preventing the sheet from substantially slipping or moving relative to the fingers when one of the fingers is placed in the openings and moved as far as possible in the first direction; and, drive means for moving the each of the fingers in at least one of the first and second directions.
10. The gripper as defined in claim 9, wherein said means for preventing the sheet from substantially slipping or moving relative to the fingers when one of the fingers is placed in the openings and moved as far as possible in the first direction is a groove within one of the fingers, said groove sized to accommodate the edge of the sheet.
11. The gripper as defined in claim 3, wherein the groove is substantially larger than the thickness of the edge of the sheet.
12. A method of gripping a sheet of material having at least an opening defined therein, comprising the steps of:
providing three fingers at least one of which is movable, the at least one finger having tracking means for being guided along a wall defining the opening;
placing the at least one finger in the opening, the fingers being spaced from one another;
and, moving the fingers toward or away from one another until movement is ceased, thefingers forming 3 vertices of a triangle.
providing three fingers at least one of which is movable, the at least one finger having tracking means for being guided along a wall defining the opening;
placing the at least one finger in the opening, the fingers being spaced from one another;
and, moving the fingers toward or away from one another until movement is ceased, thefingers forming 3 vertices of a triangle.
13. The method as defined in claim 12 wherein the tracking means comprises a groove.
14. A method as defined in claim 13, wherein the groove is substantially larger than the thickness of the sheet material, allowing for error in locating the sheet.
15. A method of gripping a three dimensional sheet of material having slots defined therein, comprising the steps of:
providing three fingers at least one of which is driven, said fingers having tracking means for being guided along walls of the slots;
placing each of the three fingers into a different slot, the slots being spaced from one another; and, moving the fingers toward or away from one another until movement is limited by slot ends being reached, wherein the fingers form three vertices of a triangle.
providing three fingers at least one of which is driven, said fingers having tracking means for being guided along walls of the slots;
placing each of the three fingers into a different slot, the slots being spaced from one another; and, moving the fingers toward or away from one another until movement is limited by slot ends being reached, wherein the fingers form three vertices of a triangle.
16. A gripper for holding a sheet of material defining an outside edge, said gripper comprising:
at least three fingers each being relatively movable in at least one of a first direction toward another and a second direction away from another, said fingers having fixing no-clamp means for engaging said outside edge of said sheet and preventing said sheet from substantially slipping or moving relative to the fingers when said fingers are moved as far as possible in one of the first direction and the second direction; and, drive means for relatively moving said fingers in at least one of said first and second directions.
at least three fingers each being relatively movable in at least one of a first direction toward another and a second direction away from another, said fingers having fixing no-clamp means for engaging said outside edge of said sheet and preventing said sheet from substantially slipping or moving relative to the fingers when said fingers are moved as far as possible in one of the first direction and the second direction; and, drive means for relatively moving said fingers in at least one of said first and second directions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US1443496P | 1996-03-28 | 1996-03-28 | |
| US60/014,434 | 1996-03-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2201059A1 true CA2201059A1 (en) | 1997-09-28 |
Family
ID=21765474
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2201059 Abandoned CA2201059A1 (en) | 1996-03-28 | 1997-03-26 | Robot gripper for fixturing a three-dimensional object |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2201059A1 (en) |
-
1997
- 1997-03-26 CA CA 2201059 patent/CA2201059A1/en not_active Abandoned
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