Robotic grasping apparatus

Abstract: A robotic grasping manipulator includes a support base (4), a fixed elongate index finger (70) which extends forwardly a certain distance from the base and then curves upwardly to terminate in a tip (76), and a two-degree of freedom elongate thumb (8) pivotally attached at a proximal end to the base to extend generally forwardly therefrom to terminate in a distal end (64) which may be moved vertically and laterally with respect to the fixed finger to thereby enable holding objects between the finger and thumb. Also included is a moveable elongate finger (100) pivotally attached at a proximal end to the base to extend forwardly a certain distance and then upwardly, generally alongside the index finger, to terminate in a distal end (108). The distal end may be moved laterally away from and toward the index finger to thereby enable holding objects between the two fingers. With the two-degree of freedom movement of the thumb and the one-degree of freedom movement of the moveable finger, a variety of different shaped objects may be grasped and held between the two fingers and thumb.

Description: This invention relates to a grasping apparatus comprising a fixed finger, having a base section, and a middle section, extending outwardly from the base section and a curved end section which extends outwardly and upwardly from the middle section to terminate in a tip having first and second lateral sides and an outermost side and an end, a moveable finger pivotally mounted to the fixed finger at a base end to pivot a free end toward and away from the fixed finger This kind of grasping apparatus is used as a robotic device. Such robotic devices and implements have been used in a variety of fields where direct human involvement is either too hazardous, too inefficient, or too monotonous and tiring. Examples of such fields include manufacturing where robots are used to carry out pickup and assembly of parts, welding, nailing and riveting, etc., handling of hazardous material such as radioactive products where direct human handling could pose a health risk, and remote handling or manipulation of articles, control panels, or other structures where on-site location of humans is desirable or possible. Also, more sophisticated, efficient and dexterous robotic apparatus is being sought for use as artificial limbs. This is especially true for implements to enable grasping and holding in a manner similar to the grasping and holding ability of the human hand. Robotic grasping implements currently available range from the simple two jaw gripping device formed similar to the jaws of a pair of pliers, to the more complicated artificial hands having three or four fingers and a thumb which may be operated to curl about objects to be grasped. Such a two jaw gripping device is known from US-A-4 225 983. In both the simple and complicated grasping implements, while larger objects can oftentimes be handled, smaller or thinner objects cannot be, especially if such objects must be picked up from a flat surface for example. Also, the number of positions or orientations in which graspable objects can be held is generally very limited with currently available grasping implements. It is an object of the invention to provide a robotic grasping apparatus with anthropomorphic characteristics. It is another object of the invention to provide a simple and easy to control robotic grasping apparatus. It is a further object of the invention to provide a grasping apparatus which is capable of holding and picking up small and thin objects as well as larger objects. It is an additional object of the invention to provide a versatile grasping apparatus for holding objects having a variety of sizes and shapes. It is still another object of the invention to provide such an apparatus capable of holding objects in a variety of positions and orientations. The above and other objects of the invention are realised according to the invention by an elongate thumb, having a fixed end mounted in the base of the finger to pivot selectively about either of two axes which are generally at right angles to one another in which both extend laterally of the long axis of the thumb, and a free end being selectively moveable to a position in contact with the end of said tip to a position in contact with the lateral sides of said tip, wherein said free end has first and second lateral sides, a contacting side, and a distal surface, and wherein said moveable finger extends generally parallel with the fixed finger, when the moveable finger is positioned against the fixed finger, and wherein the free end of the moveable finger is formed to curve upwardly alongside of the end section of the fixed finger. Such a grasping apparatus shows anthropoomorphic characteristics. It is also simple and easily to control and is capable of picking up small and thin objects as well as large objects. It is also suitable for holding objects having a variety of sizes and shapes, which can be held in a variety of positions and orientations. For example with the thumb, which moves in two degrees of freedom, the moveable finger, which moves in one degree of freedom, and the fixed finger, thin objects may be held between the thumb and either the fixed finger or moveable finger, small objects may be held between the thumb and fixed finger or between the thumb, fixed finger and moveable finger, and more bulky or elongate objects be held between the two fingers and the thumb. In accordance with another aspect of the invention, the distal surfaces of the tip of the fixed finger and the free end of the thumb are co-convex when the thumb is pivoted into contact with the fixed finger. This enables picking up of small objects from a flat surface area, for example. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which: FIG. 1 is a perspective, partially exploded view of a robotic grasping apparatus made in accordance with the principles of the present invention; FIG. 2 is a side, elevational view of the apparatus of FIG. 1; FIG. 2A is a side, partially fragmented view of the thumb and fixed index finger of the apparatus of FIG. 1; FIG. 3 is a top view of the apparatus of FIG. 1; FIG. 3A is an end view of the thumb, index finger, and moveable finger positioned together; FIG. 4 is a side, elevational view of the apparatus showing the side opposite of that shown in FIG. 2; FIG. 5 is a graphic representation of the apparatus in a two point pinch hold of a small object between the thumb and index finger; FIG. 6 is a graphic representation of the apparatus in three point pinch hold of a small object between the thumb, index finger and moveable finger; FIG. 7 is a graphic representation of the apparatus holding an elongate bar; FIG. 8 is a graphic representation of the apparatus holding a ball; FIG. 9 is a graphic representation of the apparatus holding a thin sheet between the thumb and index finger; FIG. 10 is a graphic representation of the apparatus holding a handle such as a suitcase handle; FIG. 11 is a graphic representation of the apparatus holding the head of a bolt; FIG. 12 is a graphic representation of the apparatus holding a pencil; FIG. 13 is a graphic representation of the apparatus illustrating a thumb slide operation; and FIG. 14 is a graphic representation of the apparatus holding a pair of pliers. DETAILED DESCRIPTION Referring to FIGS. 1-4, there are shown various views of one specific illustrative embodiment of a robotic grasping apparatus illustrating the principles of the present invention. This apparatus includes a housing or base 4 from which two fingers and a thumb, to be described, project and in which are contained control mechanisms for controlling the movement of one of the fingers and the thumb. The base 4 might illustratively be joined to a jointed robotic arm or other similar robotic structure by support bars 6 to enable positioning the grasping apparatus in different orientations. Such robotic arms are known in the art. A thumb 8 is pivotally joined to the base 4 to pivot about two axes 12 and 16 (FIGS. 2 and 3) both of which extend laterally of the long axis 20 of the thumb and each of which is oriented generally at a right angle to the other. The pivoting mechanism of the thumb 8 includes a yoke 24 which pivots about axis 16 and which is mounted on an axle 28 which, in turn, is rotatably fixed in the base 4 to pivot about axis 12 (FIGS. 2 and 3). This provides the thumb 8 with two degrees of freedom of movement as indicated by arrows 32a and 32b (FIGS. 1 and 2). Mounting the thumb 8, as described, involves standard mounting techniques and structure. The thumb 8 further comprises an elongate, partially angled bar 36 having a fixed or base end 36a and a free end 36b. The fixed end 36a includes a servoclamp 44 for receiving a lug 40 projecting from the yoke 24. The bar 36 is mounted on the yoke 24 by placing the servoclamp 44 on the lug 40 and then tightening the clamp by a bolt 48 to thereby secure the thumb 8 on the lug 40, all in a conventional manner. The bar 36 extends from the base end 36a a certain distance to an elbow 52 and then from the elbow at a slight angle to the free end 36b. Formed on the bottom side of the bar 36 just forwardly of the elbow 52 is a partly circular surface 56. A spur 60 projects downwardly from the underside of the bar 36 between the partly circular surface 56 and a tip 64 at the free end 36b of the bar. The thumb 8 is moveable so that the tip 64 may make contact at several surfaces with surfaces of a fixed or index finger 70 and a moveable finger 100, to next be discussed. The fixed or index finger 70 extends from the base 4 forwardly with a middle section 72 and then curves upwardly with an end section 74. The end section 74 includes a tip 76 formed with a number of surface areas to mate with certain surface areas of the tip 64 of the thumb 8. In particular, a bottom side 66 of the tip 64 of the thumb is shaped to contact and mate with a top side 78 of the tip 76 over a mutually extensive surface area when the thumb is pivoted downwardly onto the tip 76. When the thumb 8 is pivoted down onto the top side 78 of the index finger 70, a distal surface 67 of the thumb and a distal surface or outermost side 79 of the index finger are formed to be coplanar with one another at the point of contact between the thumb and index finger and are thus continuous, without break from one surface to the other. The surfaces 67 and 79 are generally convex, as best seen in FIG. 2A, to facilitate grasping or seizing of small objects between the thumb and index finger from a flat surface, for example. A lateral side 68 of the tip 64 of the thumb 8 is shaped to contact a lateral side 80 of the tip 76 of the index finger 70 over a mutually extensive surface area, when the thumb is pivoted laterally to a position in contact with the side 80 of the index finger. This, of course, allows for grasping objects between the surface area 68 and surface area 80. The surface area 80 of the index finger 70 is also formed with a cutout portion 81, as best seen in FIG. 3A, to define two generally flat surface portions 80a and 80b which form an angle of 120° with respect to one another. Facing surface 102 of the finger 100 is formed to be generally parallel with surface portion 80a to allow for gripping a hexagon nut or bolt head between the index finger 70 and moveable finger 100, with two adjacent sides of such a nut or bolt being placed against surface portions 80a and 80b of the index finger 70, and another side being placed against surface 102 of moveable finger 100. The cutout portion 81 also accommodates the tip 64 of the thumb between the index finger 70 and the moveable finger 100. Another lateral side 69 of the tip 64 of the thumb 8 (FIGS. 3 and 4) is shaped to contact lateral side 82 of the tip 76 of the index finger 70 over mutually extensive surface areas, when the thumb is pivoted laterally to a position in contact with the side 82. Again, objects may thus be held between the thumb 8 and side 82 of the index finger. The moveable finger 100 is pivotally mounted in the middle section 72 of the index finger 70, near or at the base 40, to move laterally away from and toward the index finger. An opening 84 is formed in the middle section 72 to receive a proximal end 104 of the moveable finger 100 which is pivotally mounted on a pin 86 which extends between two ears 87 and 88 which, in turn, project generally in parallel from the side of the index finger 70 opposite that on which the moveable finger is positioned. The moveable finger 100 includes a free end 108 which extends from the proximal end 104 generally parallel with the index finger 70. The free end 108 of the moveable finger 100 is formed to curve along side of the end section 74 of the index finger 70 as best seen in FIGS. 1 and 4. The tip of the free end 108 of the moveable finger 100 is formed to contact and mate with the underside 66 of the tip 64 of the thumb 8, to hold objects therebetween. The thumb 8 is thus moveable over a range to mate with the ends or tips of the index finger 70 and the moveable finger 100. When the moveable finger 100 is pivoted against the index finger 70, a cutout portion or notch 81 between the moveable finger and index finger allows for pivoting the tip 64 of the thumb 8 therebetween, as indicated earlier (FIG. 3A). As with the thumb 8, portions of the index finger 70 and moveable finger 100 may be removed and reattached as needed. Specifically, the end section 74 of the index finger may be removed by simply unscrewing set screws 75 which extend through openings in the end section and corresponding openings in a projection 73 of the middle section 72, when the projection 73 is fitted into a notch or groove 77 formed in the end section 74. When the set screws 75 are removed, the end section 74 may simply be removed from the middle section 72 and serviced, replaced, etc. In a similar fashion, the free end 108 of the moveable finger 100 is detachably mounted on the proximal end 104 of the finger. Effecting pivoting of the thumb 8 and moveable finger 100 may be carried out in any conventional fashion. For example, the proximal end 104 of the finger 100 may be formed with a fork 105 (FIGS. 1 and 2), between which is pivotally mounted a push rod 107 for pushing or pulling on the fork to cause the finger to pivot. Pivoting of the thumb 8 could be controlled in a similar fashion, with the controlling mechanisms located in the base 4. With the apparatus of FIGS. 1-4, a versatile grasping and holding robotic implement is provided. This apparatus utilizes a single fixed finger, a one degree of freedom of movement moveable finger, and a two degree of freedom of the movement thumb to provide for grasping and holding a variety of different shaped objects. To accommodate holding elongate objects, a groove 112 is formed in the base housing (palm) 112. As will be discussed later, an elongate object placed between the thumb 8, on one side, and the fingers 70 and 100, on the other side, would also rest in the groove 112. FIGS. 5-14 are graphic representations of the apparatus of FIGS. 1-4 illustrating various objects which can be grasped and the manner in which they can be grasped. FIG. 5 shows a two-point pinch grasp in which a small three dimensional object 204 is held between the thumb 8 and index finger 70 in a manner similar to a human hand pinching an object between the index finger and opposing thumb. This grasp is effective for picking up and holding small objects. FIG. 6 shows a three-point pinch grasp in which an object 208 is held between the thumb 8, index finger 70, and moveable finger 100. This grasp is similar to a human hand pinching an object using the index finger, middle finger and opposing thumb. This grasp is a somewhat more stable way of holding larger objects than that shown in the FIG. 5 grasp (even though the object shown in FIG. 6 is the same size as that shown in FIG. 5). FIG. 7 shows a wrap grasp in which a bar 210 is held between the index finger 70 and moveable finger 100 on one side and the thumb 8 on the other side, with the bar being further constrained by the groove 112 in the base 4. Tools and implements having handles, such as hammers, hose, shovels, etc., may be held with the wrap grasp shown in FIG. 7 FIG. 8 shows a spherical grasp in which a ball 214 is held between the two fingers and thumb, but more rearwardly (and against the base 4) than with the three-point pinch of FIG. 6. FIG. 9 shows a lateral-pinch grasp in which a sheet of material, file folder, and the like is held between the index finger 70 and the thumb 8, with the thumb pressing the object against the side of the index finger. This grasp is especially suitable for holding cards or other flat articles when such cards are to be inserted into and removed from locations where the edges of the cards are accessible. FIG. 10 shows a type of loop grasp, for holding suitcase handles, mug handles, telephone receivers, etc., in which a handle 222 is held by the thumb 8 against the curved free end portions of the index finger 70 and moveable finger 100. With this grasp, the loads are supported by the index finger and moveable finger and so the lifting capability is independent of the clamping force provided by the thumb 8. FIG. 11 shows the grasping apparatus holding the hexagonal-side head of a bolt, where two sides of the head are positioned against surface portions 80a and 80b of the index finger 70. The head of the bolt 226 is also held by the free or distal ends of the fingers 100 and thumb 8 which are positioned against other respective other sides of the bolt head. FIG. 12, as is clear from the figure, shows a pencil/pen grasp in which a pencil or pen 230 is held near the writing end between the thumb 8, index finger 70 and moveable finger 100, with the rear end of the pen or pencil extending rearwardly over the base 4 of the apparatus. FIG. 13 shows a thumb-slide operation in which the thumb 8 is moved in a sliding motion over one side of the index finger 70. This operation might be used to start nuts on bolts, threading fasteners together, and similar objects where a human index finger-sliding over the thumb motion is required. FIG. 14 shows the grasping apparatus of the present invention holding the handles of a pair of pliers 234. As shown, handle 234a of the pliers is held securely between the index finger 70 and moveable finger 100, while the thumb 8 may be moved to press the other handle 234b of the pliers downwardly to close the pliers. It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the scope of the appended claims.

Claims: Grasping apparatus comprising a fixed finger (70), having a base section (4), a narrowed middle section (72), extending from the base section (4) and a curved end section (74) which is curved in one plane and extends from the middle section (72) to terminate in a tip (76) having first and second sides (80, 82) that are lateral in respect to the curve in the meaning that they form neither concave nor convex surface portions of said curve in said one plane, an outermost side (79), which is on the outside of the finger so as to form at least part of the curved surface area of said curve in said one plane and an end (78), a moveable finger (100), which is also curved in one plane, pivotally mounted to the fixed finger (70) at a base end (104) to pivot a free end (108) toward and away from the fixed finger (70), characterised in that the moveable finger (100) is pivotable about an axis which lies in the plane in which the fixed finger is curved, such that curving of the moveable finger lies generally in the same plane as the curving of the fixed finger (70) when the moveable finger (100) is positioned against the fixed finger (70), and wherein the free end (108) of the moveable finger (100) is formed to curve alongside the end section (74) of the fixed finger (70) and in that the grasping apparatus further comprises an elongate thumb (8) having a fixed end (36a) mounted in the base (4) of the fixed finger (70) to pivot selectively about either of two axes (12, 16), which are generally at right angles to one another and which both extend laterally of the long axis of the thumb (8), and a free end (36b) being selectively moveable to a position in contact with the end of said tip (76) and to a position in contact with the lateral sides (80, 82) of said tip (76), wherein said free end (36b) having first and second lateral sides (68, 69), a contacting side (66) and a distal surface (77). Grasping apparatus as in claim 1 wherein the contacting side (66) of the free end (36b) of the thumb (8), and the end (78) of said tip (76) are formed with mutually conformable contact surfaces. Grasping apparatus as in claim 1 or 2 wherein the distal surface (67) of the free end (36b) of the thumb (8) and the surface of the outermost side (79) of the tip (76) of the finger are formed to be co-planer with the contacting side (66) of the thumb (8) and the end (78) of the tip (76) are in contact. Grasping apparatus as in one of claims 1 to 3 wherein said surfaces are generally convex. Grasping apparatus as in one of claims 1 to 4 wherein the first lateral side (68) of the free end (36b) of the thumb (8) and the second lateral side (80) of the tip (76) are formed with mutually conformable contact surfaces. Grasping apparatus as in one of claims 1 to 5 wherein the second lateral side (69) of the free end (36b) of the thumb (8) and the first lateral side (82) of the tip (76) are formed with mutually conformable contact surfaces. Grasping apparatus as in one of claims 1 to 6 wherein said end section (74) of the finger (70) is formed so that the tip (76) is generally at the right angle with respect to the middle section (72). Grasping apparatus as in one of claims 1 to 7 wherein said thumb (8) is mounted so that the free end (36b) maybe moved downwardly to contact the end of said tip (76), upwardly away from the end (78) of said tip (76), laterally toward the second lateral side (80) of the tip (76), laterally away said second lateral side (80) of the tip (76), laterally toward the first lateral side (82) of the tip (76) and laterally away from the first lateral side (82) of the tip (76). Grasping apparatus as in one of claims 1 to 8 wherein a bottom side (66) of the thumb (8) rearwardly of the free end (76b), generally faces the fixed finger (70) and is formed with a generally concave surface area (56). Grasping apparatus as in one of claims 1 to 9 wherein said concave surface (56) area is generally partly-circular. Grasping apparatus as in one of claims 1 to 10 wherein the end section (74) of the fixed finger (70) is removeably mounted on the middle section (72) of the finger. Grasping apparatus as in one of claims 1 to 11 wherein the free end (36b) of the thumb (8) is removeably mounted on the fixed end (36a) of the thumb (8). Grasping apparatus as in one of claims 1 to 12 wherein the contacting side (66) of the free end (36b) of the thumb (8), and a free end (108) of the moveable finger (100) are formed with mutually conformable contact surfaces. Grasping apparatus as in one of claims 1 to 13 wherein said thumb (8) is mounted so that the free end (36b) thereof maybe moved toward and away from the area between the fixed finger (70) and the moveable finger (100). Grasping apparatus as in one of claims 1 to 14 wherein facing surfaces (102) of the free end (108) of the moveable finger (100) in the end section (74) of the fixed finger (70) are sculptured to receive therebetween the free end (36b) of the thumb (8). Grasping apparatus as in one of claims 1 to 15 wherein the surface of the fixed finger (70) is formed with first and second generally flat surface portions (80a, 80b) disposed at an angle of 120° from one another, and wherein the facing surface (102) of the moveable finger (100) is formed to be generally parallel with the first surface portion (80a) of the fixed finger (70) when the moveable finger (100) is moved to a position against the fixed finger (70). Grasping apparatus as in one of claims 1 to 16 wherein said thumb (8) is mounted so that the free end (36b) may be moved in planes which are above and generally parallel with the plane in which the moveable finger (100) moves. Grasping apparatus as in one of claims 1 to 17 wherein said fixed finger (70) includes and opening (84) formed in the middle section (74) thereof to receive the base end (104) of the moveable finger (100), and a pin (86) disposed perpendicularly to the plane in which the moveable finger (100) moves and on which the base end (104) of the moveable finger (100) is pivotally mounted. Grasping apparatus as in one of claims 1 to 18 wherein the base end (104) of the moveable finger (100) extends from the pin (86), through the opening (84) in the middle section (74) of the fixed finger (70) to said one side of the fixed finger (70), and wherein the free end (108) of the moveable finger extends at an angle from the base end (36a) along side of the fixed finger (70) when the moveable finger (100) is pivoted to a postition against the fixed finger (70). Grasping apparatus as in one of claims 1 to 19 wherein the free end (108) of the moveable finger (100) is detachably mounted to the base end (104) thereof. Grasping apparatus as in one of claims 1 to 20 wherein the base section (36a) of the fixed finger (70) is formed with a groove (112) for receiving one end of the elongate object (210) held between the fixed finger (70) and moveable finger (100), one side of the object, and the thumb (8), on the other side. Grasping apparatus as in one of claims 1 to 21, characterized by the facing sides of the tip (76) of the index finger (70) and a distal end (104) of the moveable finger being formed to define a U-shaped gap (81) between the fingers and the moveable finger (100) being pivoted to a position against the index finger (70), said gap (81) being dimensioned to receive the distal end (36b) of the thumb (8). A grasping apparatus as in one of claims 1 to 22 wherein the bottom side (66) of the distal end (36b) of the thumb (8) is shaped to contact the tip (76) of the index finger (70) over a mutually extensive survace area, when the thumb (8) is pivoted downwardly to a position in contact with the index finger (70). A grasping apparatus as in one of claims 1 to 23 wherein lateral sides of the distal end of the thumb (8) are shaped to contact corresponding lateral sides of the tip of the index finger (70) over corresponding mutually extensive surface areas, when the thumb (8) is pivoted laterally to positions in contact with respective sides of the tip of the index finger (70). A grasping apparatus as in one of claims 1 to 24 where the facing side (80) of the tip (76) of the index finger (70) is formed with a first surface area (80a) spaced from and generally parallel with the facing side (102) of the distal end (64) of the moveable finger (100), and a second surface area (80b) contiguous with the first surface (80a) and extending downwardly therefrom toward the facing side (102) of the distal end (64) of the moveable finger (100), at an angle of about 120° from the first surface area (80a). A grasping apparatus as in one of claims 1 to 25 wherein the distal end (108) of the moveable finger (100) is shaped to contact a bottom side (66) of the distal end (64) of the thumb (8) over a mutually extensive surface area, when the thumb is pivoted downwardly to a position in contact with the moveable finger (100). A grasping apparatus as in one of claims 1 to 26 wherein a bottom side of the thumb is formed with a partially circular notch (81) into which objects may be received when held between the index finger (70) and the thumb (8). A grasping apparatus as in one of claims 1 to 27 wherein the index finger (70) is detachably mounted on the base (4), wherein the distal end (36b) of the thumb (8) is detachably mounted on the proximal end (36a) thereof and wherein the distal end (108) of the moveable finger (100) is detachably mounted on the proximal end (104) thereof. Grasping apparatus as in one of claims 1 to 28, characterized by said base (4) being formed with a groove (112) at a location generally adjacent the location of the attachment of the index finger (70), to receive and hold one end of a long object being held between the fingers (70, 100) and the thumb (8).

Inventors: JACOBSEN STEPHEN C, SMITH FRASER, JACOBSEN, STEPHEN C., SMITH, FRASER
Applicants: SARCOS INC, SARCOS, INC.
Application year: 1991
Main classification: B25J15
IPC codes: A61F2, B25J15