Abstract:
A grasping apparatus ( 10 ) has multiple fingers ( 64 ) joined within slots ( 56 ) in the face of a moving piston ( 50 ) within a fluid cylinder ( 20 ). As the piston ( 50 ) moves, cams ( 62 ) joined to the fingers ( 64 ) are rotated so as to close or open the fingers ( 64 ) which are radially mounted. Once actuated the piston ( 50 ) is returned to its relaxed position by a spring ( 70 ) when fluid pressure is released.

Description:
This application is a 371 of PCT/US98/13021 filed Jun. 24, 1998 and is based upon and uses the technology defined and described in a U.S. Provisional patent application, Ser. No. 60/050,896 filed Jun. 26, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention related generally to robotic grasping devices, and more particularly to an articulated grasping apparatus having opposing digits capable of closing onto an article for the purpose of engaging such an article in order to place or position the article. 
     2. Description of Related Art 
     The following art defines the present state of this field: 
     Sokolow, U.S. Pat. No. 3,981,673 describes an apparatus for transferring parisons from an oven to a blow mold has the capability of straightening up titled parisons and gripping them uniformly without flattening the ends. The apparatus includes a gripper with jaws which open wide when opened, thereby providing an entry space between the jaws for titled parisons as well as an upright parison and which in the closed position form an essentially complete circle about the parison to uniformly grip the same in cooperation with a push piece which moves into the open end of the parison. 
     Evans et al., U.S. Pat. No. 3,651,958 describes a transfer carriage movable between a station and a machine tool having a pair of work carriers movable independently along intersecting paths operable to pick up a work piece and to deposit in its place another work piece, both at the station and at the machine tool. 
     Bende, U.S. Pat. No. 3,400,836 describes an apparatus for grasping, holding and transferring a work piece on a high speed production line. The clamp is biased to the closed position to prevent slippage of the work piece during transfer. Cam controls regulate the movement of the clamp from a folded or stored position to a grasping position and then closed and open the clamp at the appropriate time in the cycle of the apparatus. 
     Panyard, U.S. Pat. No. 5,588,794 provides a gripper for mounting to a distal end of a robotic arm for gripping a work piece having a pair of spaced apart longitudinally extending contoured faces and at least two extending cylindrical bores, each cylindrical bore having an inner surface, the gripper including a base, a pair of spaced apart longitudinally extending stabilizing members each affixed to the base, each of the stabilizing members having an engagement surface adapted to abuttingly engage a respective contoured face of the work piece, at least one pair of opposing clamping arms, each clamping arm being pivotal from a first position wherein the clamping arm is disposed adjacent a respective cylindrical bore to a second position wherein the clamping arm abuttingly engages the inner surface of a cylindrical bore, a pair of biasing cylinder means connected to one of said pair of clamping arms for moving said one clamping arm from said first position to said second position, a pair of spaced apart compliant devices affixed to the base for releasably connecting the base to the distal end of the robotic arm and a control system for selectively controlling the actuation of the biasing cylinders. 
     Inaba et al., U.S. Pat. No. 4,540,212 describes an industrial robot hand having swing fingers for gripping a work pivotally mounted on a hand base member which is attached to the free end of a wrist unit, said swing fingers being members formed of a sheet metal through a pressing process in a U-shaped cross-section, and said swing fingers having a U-shaped cross-section and a hydraulic actuator linked together with chain pin links. 
     Asamoto, U.S. Pat. No. 3,945,676 describes a gripping device for use in an industrial robot or manipulator including a pair of clamp arms mounted on a base plate of the device and connected with a clamp arm operating rod through a pair of links and a cylinder-piston assembly having a misgrip detecting mechanism. One of the pair of clamp arms is shorter than the other clamp arm and is provided with an additional clamp arm swingable with respect to the sort clamp arm. The misgrip detecting mechanism is operated by the action of a pressure switch provided in a hydraulic fluid conduit connected between the hydraulic fluid supplying source and a pressure chamber formed within the cylinder-piston assembly. Thus, the gripping device can positively and effectively grip a work piece. 
     McGill, U.S. Pat. No. 3,125,370 relates to article grippers, and particularly to apparatus for picking up articles such as bottles, containers or the like, transporting them a distance, and then depositing the articles in a second position. The general object of the present invention is to provide novel and improved bottle gripper apparatus characterized by the self-centering action thereof when any of the bottle grippers are moved laterally from their normal centered position. A further object of the invention is to provide a pivotally positioned substantially parallelogram shaped means in the assembly of gripping jaws and associated controls in article grippers and wherein a pair of laterally spaced lost-motion connecting means are present and have associated compressed coil springs urging the lost motion means to the extremities of their positions normally, but with one such lost motion means being adapted to be moved outwardly of the parallelogram when the article grippers are moved laterally to further compress on positioned coil spring means and aid in snapping the means back into a normal centered position when the external force applied thereto is removed. 
     The prior art teaches similar devices to the instant invention which are useful for similar application. However, the prior art does not teach a grasping device of such compact design and wherein sliding members of the actuated fingers are engaged and movable within the material that makes-up a fluid piston. This inventive concept provides significant advantages in miniaturization, clearance requirements when in use, and simplicity of operation. The present invention fulfills these needs and provides further related advantages as described in the following summary. 
     SUMMARY OF THE INVENTION 
     The present invention teaches certain benefits in construction and use which give rise to the objectives described below. 
     The present invention provides a grasping apparatus having multiple fingers joined to a moving piston within a fluid driven cylinder such as an air cylinder. As the piston moves, cams joined to the fingers are rotated so as to close or open the fingers which are radially mounted. Once actuated, the piston is returned to the relaxed position by a spring. 
     A primary objective of the present invention is to provide a grasping apparatus having advantages not taught by the prior art. 
     Another objective is to provide such a grasping apparatus with an adjustable range of grasping capability by adjustment of individual fingers of the device. 
     A further objective is to provide such a grasping apparatus that is highly compact and simple in construction as compared to the prior art. 
     A still further objective is to provide such a grasping apparatus that is air actuated but with a spring return so as to eliminate complex valve arrangements. 
     Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The accompanying drawings illustrate the present invention. In such drawings: 
     FIG. 1 is an exploded perspective view of the preferred embodiment of the present invention shown from a fluid inlet end and with four fingers shown in the actuated position; 
     FIGS. 2 and 3 are sectional views taken along line  2 — 2  of FIG. 1, but adapted by rotating the grasping means of the invention into the plane of the paper, and showing the apparatus as assembled and in a relaxed position (FIG.  2 ), and in an actuated position (FIG.  3 ). 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The above described drawing figures illustrate the invention, a fluid actuated, articulated grasping apparatus  10  comprising, as shown in FIG. 1, a fluid cylinder  20  having a conduit means  22 , i.e., through holes, for admitting a fluid into a first side  24  (FIG. 3) of the fluid cylinder  20  and an actuating rod  30  axially positioned within the fluid cylinder  20 , a proximal end attachment portion  32  of the actuating rod  30  extending outwardly from an end wall  26  of the fluid cylinder  20  and held thereon by an engaging fluid inlet and securement means  40 . 
     A piston  50  is adapted by a sealing ring  52  for fluid forced linear motion within the fluid cylinder  20 , the piston  50  providing an axial aperture  54  for tight-fitting sliding engagement along the actuating rod  30  and a plurality of radially oriented grasping means  60 , each of the grasping means  60  providing a cam portion  62  and a finger portion  64 , as best seen in FIG. 2, the cam portion  62  being pivotally joined, at first pin means  65 , with a distal end  34  of the actuating rod  30  and pivotally and slidingly joined, at second pin means  69 , with a radially positioned slot means  56 , within piston  50 , in such manner that as the piston  50  moves along the actuating rod  30  away from the end wall  26  of the fluid cylinder  20 , the finger portions  64  of the plurality of grasping means  60  converge, and conversely, when the piston  50  moves toward the end wall  26  of the fluid cylinder  20 , the finger portions  64  of the grasping means  60  diverge, and in both movements of the grasping means  60 , the second pin means  69  moves linearly and radially within the radially positioned slot means  56 . 
     A spring biasing means  70  is fitted about the actuating rod  30  and is adapted, by its length and spring constant, for urging the piston  50  toward the end wall  26  of the fluid cylinder  20 . Therefore, when fluid is injected into the fluid cylinder  20  through the fluid conduit means  22 , as shown graphically in FIG. 3, the fluid cylinder tends to move the piston  50  away from the end wall  26  of the fluid cylinder  20  and compresses the spring biasing means  70 , thereby storing spring potential energy; while when fluid is allowed to exit the fluid cylinder  20  through the fluid conduit means  22 , the spring biasing means  70  forces the piston  50  toward the end wall  26  of the fluid cylinder  20  thereby releasing its stored energy. 
     The cam portion  62  and the finger portion  64  of each of the grasping means  60  may be formed as a single integral part as is well known in the art. Alternatively, the finger portion  64  of each of the grasping means  60  may be adapted for positional adjustment on its respective cam portion  62  so as to enable the grasping means  60  to adapt to a desired range of grasping articulation, i.e., a larger range of motion or a smaller range of motion. As will be seen in FIG. 3, cam portion  62  may have a threaded hole  67 , while finger portion  64  may have a plurality of corresponding clearance holes  66 , holes  66  and  67  being designed for accommodating hex-socket head screws  68  for fastening the finger portion  64  at a selected position relative to cam portion  62 . 
     A cover plate  80  is adapted, by its size and shape, for engaging an open end  28  of the fluid cylinder  20 , the cover plate  80  providing a radial slot means  82  for accommodating movement of the grasping means  60  therein and an annular shoulder  86  for positioning the spring bias means  70  as well as acting as a stop surface therefor. Note that distal end  34  of actuating rod  30  is adapted by its diameter for capturing cover plate  80  so as to hold coverplate  80  tightly within the open end  28  of the fluid cylinder  20  when fluid inlet and securement means  40  is tightened onto the proximal end  32  of the actuating rod  30 . 
     Preferably, the proximal end  32  of the actuating rod  30  and the engaging fluid inlet and securement means  40  are joined by a screw thread means  42 , i.e. a male machine thread on the actuating rod  30  and a corresponding female machine thread on the fluid inlet and securement means  40 . 
     While the invention has been described with reference to at least one preferred embodiment, it is to be clearly understood by those skilled in the art that the invention is not limited thereto. Rather, the scope of the invention is to be interpreted only in conjunction with the appended claims.