Abstract:
A device for gripping an object including a gripper head, an actuator, and a cable assembly. The gripper head includes at least one movable jaw. The actuator is located remotely from the gripper head. The cable assembly connects the gripper head to the actuator and is configured to drive the gripper head by the actuator.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a non-provisional application based upon U.S. provisional patent application Ser. No. 61/718,772, entitled “GRIPPER WITH REMOTE CABLE DRIVE”, filed Oct. 26, 2012, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to grippers, and, more particularly, to grippers that have at least one movable jaw. 
         [0004]    2. Description of the Related Art 
         [0005]    Grippers are mechanical devices characterized by one or more jaws that are moved together or apart by motive means such as an electric motor or pneumatic piston. Once moved into a position of contact with the gripped workpiece, the jaws produce a gripping force against the workpiece so that the position of the workpiece might be subsequently translated or rotated. It is often desirable to minimize the mass of the gripper, especially in applications involving integration of the gripper as an end effector onto robots, where the mass of the gripper correspondingly reduces the mass of the workpiece that the robot can manipulate. Physically separating the components of the gripper responsible for moving and guiding the jaws from those components responsible for generating the motive force provides an effective means of reducing the mass that the robot must manipulate. Historically, this component separation has been accomplished by the use of fluid power transmission. A pump or compressor, often located some distance away from the robot, provides pressurized fluid through an appropriate network of valves, pipes, and flexible tubes to a piston that moves the gripping jaws. Only the piston and those components required to move and guide the jaws are mounted on the movable portion of the robot. However, there are applications that dictate the use of electric power as a motive means. Electric motors are typically employed in these applications to convert electric current into torque, with the torque subsequently converted into linear force to drive the gripping jaws. Williams, et al, disclose such prior art in U.S. Pat. No. 8,152,214 B2. Methods used in the prior art to couple the mechanical output of the motor to the mechanism moving the jaws typically necessitate close physical proximity of the motor to the jaws. Such methods suffer the disadvantage of adding the relatively large mass of the motor to the total mass that a robot or machine must move when the gripper is used as an end effector. 
         [0006]    What is needed in the art is a gripper with less integrally associated mass that the gripper must carry during operation. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is directed to a gripper that includes a gripper head with at least one movable jaw; an actuator located remotely from the gripper head; and a cable assembly that connects the actuator to the gripper head and is configured to drive the gripper head by the actuator. 
         [0008]    An advantage of the present invention is that the relatively heavy actuator driving the gripper head doesn&#39;t need to be carried by the gripper during operation, which allows the gripper to handle workpieces with more mass. 
         [0009]    Another advantage of the present invention is that motors can be used to remotely drive the gripper head, allowing those skilled in the art to have greater versatility in components to drive the gripper head. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0011]      FIG. 1  is an exploded perspective view of an embodiment of the invention; 
           [0012]      FIG. 2  is a perspective view of an embodiment of a cable assembly of the invention; 
           [0013]      FIG. 3  is a cross-sectional perspective view of an embodiment of a cable assembly of the invention; 
           [0014]      FIG. 4  is a multi-perspective exploded view of an embodiment of a force transmitter of the invention; 
           [0015]      FIG. 5  is a perspective view of another embodiment of a cable assembly of the invention; 
           [0016]      FIG. 6  is a cross-sectional perspective view of another embodiment of a cable assembly of the invention; 
           [0017]      FIG. 7  is a perspective and partially cross-sectional view of another embodiment of a cable assembly of the invention; 
           [0018]      FIG. 8  is an exploded perspective view of yet another embodiment of the invention; 
           [0019]      FIG. 9  is an exploded perspective view of yet another embodiment of the invention; 
           [0020]      FIG. 10  is a perspective view of yet another embodiment of a cable assembly of the invention; 
           [0021]      FIG. 11  is a perspective cross-sectional view of yet another embodiment of a cable assembly of the invention; 
           [0022]      FIG. 12  is a multi-perspective view of another embodiment of a force transmitter of the invention; 
           [0023]      FIG. 13  is a multi-perspective view of another embodiment of a force transmitter of the invention; and 
           [0024]      FIG. 14  is an exploded perspective view of yet another embodiment of the invention. 
       
    
    
       [0025]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown a gripper which generally includes a gripper head  20  that includes the gripping jaws and those components responsible for moving and guiding the jaws. A cover  22  is attached to the gripper head  20  with threaded fasteners  24 . A ferrule  26  is attached to the cover  22  by adhesive bonding or other suitable means. An output end  30 , shown in  FIG. 1  as a rod, of a cable assembly  28  passes through axially aligned holes in the ferrule  26  and in the cover  22  and is attached by threading or other suitable means to the appropriate component within the gripper head  20  responsible for moving the gripper jaws. The opposing end of the ferrule  26  is threaded or adhesively bonded onto the distal end of a sheath  34  of the cable assembly  28  (see also  FIG. 3 ). The proximal end of the sheath  34  is threaded or adhesively bonded into a ferrule  36 . The opposing end of the ferrule  36  is attached to a motor housing  38  by adhesive bonding or other suitable means. An input end  32 , shown as a rod, of the cable assembly  28  passes through a hole in the motor housing  38  and is threaded into a rack  40 . A pinion  42  is engaged into the rack  40  and coupled to the shaft of an actuator  44 , shown here as a motor, to convert the rotary motion of the motor  44  into a corresponding linear motion of the rack  40  and in turn, into a corresponding linear motion of the output end  30  to move the gripper jaws. While  FIG. 1  shows a linear converter embodied as a rack  40  and a pinion  42 , those skilled in the art will appreciate that any component capable of converting rotary motion into linear motion can be used in the place of the rack  40  and the pinion  42 . Threaded fasteners  46  attach the motor  44  to the motor housing  38 . A cover  51  is attached with threaded fasteners  50  to close the open cavity in the motor housing  38 . 
         [0027]    Although  FIGS. 1-14  show and reference an actuator driving the gripper as a rotary electric motor, it is understood that such an embodiment may also be applied to a gripper including a linear electric motor, or a piston and cylinder arranged to generate motive force. It is also understood that the embodiment may be applied to any type or style of gripper in order to physically separate the components of the gripper responsible for moving and guiding the jaws from those components responsible for generating the motive force. It is further understood that such an embodiment may also be applied to actuators or end effectors other than grippers without changing the substance of the invention. 
         [0028]    The cable assembly  28  can be any construction capable of transmitting both tensile and compressive forces, while allowing sufficient flexure to accommodate relative motion between the gripper head  20  and actuator. Ideally, the transmission of the tensile and compressive forces though the cable assembly  28  occurs with minimal or substantially no parasitic loss so that the majority of the force applied to the input end  32  of the cable assembly  28  is available at the output end  30  to move the jaws of the gripper. Such cable assemblies are used in the steering systems for small marine vessels. 
         [0029]      FIGS. 2 ,  3  and  4  show one embodiment of the cable assembly  28 .  FIG. 3  shows a section view along the longitudinal axis of the cable assembly  28 . A short length of the cable assembly  28  is shown for illustrative purposes and it is understood that the overall length of the cable assembly  28  can be increased or decreased as desired.  FIG. 4  shows rendered perspective views of a spherical bead  53 . The input end  32  and output end  30  bound a plurality of spherical beads  53  and a cable  52 , which are surrounded by a flexible sheath  34 . The cable  52  can include a braid of polymer filaments, although cables including braided or twisted metal strands can also be used. The proximal end of the cable  52  is adhesively bonded into a complimentary central bore in the input end  32 . A central bore  56  in each bead  53  allows the plurality of beads to be strung along a length of the cable  52 . A complimentary spherical cavity  54  on one end of each bead  53  allows each bead  53  to nest and be nested by adjacent beads  53  so that the column of beads shares a common centerline. As the cable assembly  28  is laterally flexed, each bead  53  is free to rotate unencumbered about the center of its spherical diameter while maintaining a common line of contact with an adjacent bead. In this manner, the line of contact between each adjacent pair of beads remains normal to the radius of curvature of the flexed sheath  28 . The input end  32  and output end  30  possess a spherical radius on one end and a complimentary spherical cavity on the opposing end in an analogous manner to the beads  50 . The spherical radius on the end of the input end  32  allows the end to nest into the complimentary spherical cavity  54  on the first bead  53  on the proximal end of the cable assembly  28  and the spherical cavity on the end of the output end  30  allows the end to nest over the spherical radius of the last bead  53  on the distal end of the cable assembly  28 . The distal end of the cable  52  passes through a complimentary central bore in the output end  30 . The cable  52  is stretched to remove all clearance between the input end  32 , beads  53  and the output end  30  and create a desired level of tension in the cable. While in this stretched state, the distal end of the cable  52  is adhesively bonded to the bore in the output end  30 . The tensioned column of the input and output ends  32 ,  30  and beads  53  is inserted through the inner bore of the sheath  34  to complete the cable assembly  28 . The resulting cable assembly  28  is capable of transmitting compressive force from one end of the assembly to the other end as each spherical bead  53  presses against an adjacent bead in the column. The cable assembly  28  is also able to transmit tensile force through the cable  52 . 
         [0030]      FIGS. 5 ,  6  and  7  show another embodiment of the cable assembly  28 .  FIG. 6  shows a section view along the longitudinal axis of the cable assembly  28 . A short length of the cable assembly  28  is shown for illustrative purposes and it is understood that the overall length of the assembly can be increased or decreased as desired.  FIG. 7  shows a partially sectioned perspective view of the cable assembly  28 . The input end  32  and output end  30  bound a length of a helical extension spring  60  and a cable  52 , which are surrounded by a flexible sheath  34 . The cable  52  can include a braid of polymer filaments, although cables including braided or twisted metal strands can also be used. The proximal end of the cable  52  is adhesively bonded into a complimentary central bore in the input end  32 . The distal end of the cable  52  passes through a complimentary central bore in the output end  30 . The cable  52  is stretched to remove all clearance between the input end  32 , helical extension spring  60  and output end  30  and create a desired level of tension in the cable  52 . While in this stretched state, the distal end of the cable  52  is adhesively bonded to the bore in the output end  30 . The tensioned column of the input and output ends  32 ,  30  and spring  60  is inserted through the inner bore of the sheath  34  to complete the cable assembly  28 . The resulting cable assembly  28  is capable of transmitting compressive force from one end of the cable assembly  28  to the other end as each spring winding  60  presses against an adjacent winding. The assembly is also able to transmit tensile force through the cable  52 . 
         [0031]      FIG. 8  shows another embodiment of the invention. A gripper head  20  includes the gripping jaws and those components responsible for moving and guiding the jaws. A cover  22  is attached to the gripper head  20  with threaded fasteners  24 . Ferrules  26  are attached to the gripper cover  22  by adhesive bonding or other suitable means. An output end of a cable  52  of a cable assembly  28  passes though axially aligned holes in the ferrule  26  and in the cover  22 ; wraps tangentially around a pulley  72 , and exits the cover  22  and ferrule  26  though axially aligned holes in the cover  22  and ferrule  26 , respectively. The ferrule  26  is threaded or adhesively bonded onto the distal end of a sheath  34  of the cable assembly  28 . The ferrule  26  is threaded or adhesively bonded onto the distal end of a sheath  34 . The proximal end of the sheath  34  is threaded or adhesively bonded into a ferrule  36 . Ferrules  36  are attached to a motor cover  51  by adhesive bonding or other suitable means. Threaded fasteners  50  attach the motor cover  51  to a motor housing  38 . The input end of the cable  52  of the cable assembly  28  passes though axially aligned holes in the ferrule  36  and in the motor cover  51 ; wraps tangentially around a pulley  70 , and exits the cover  51  and ferrule  36  though axially aligned holes in the cover and ferrule, respectively. The pulley  70  is coupled to the shaft of an actuator  44 , shown here as a motor, to convert the rotary motion of the motor  44  into a corresponding linear motion of the cable assembly cable  52 , which is free to slide axially within sheath  34 . Threaded fasteners  46  attach the motor  44  onto the motor housing  38 . The ends of a shaft  74  are contained in complimentary grooves (not shown) in the interior of the gripper cover  22 , which prevent translation of the shaft  74  while allowing unencumbered shaft rotation. A pulley  72  and a pinion  42  are coupled to the shaft  74 , so that rotational motion of the pulley  72  causes a corresponding rotation of the pinion  42 . The pinion  42  is engaged into a rack  40  to convert the rotary motion of the pulley  72  into a corresponding linear motion of the rack  40  to move the gripper jaws. The cable  52  engages the input pulley  70  and output pulley  72  with means that prevent the tangential movement of the cable  52  with respect to the pulleys. In this manner, rotation of the input pulley  70  causes a corresponding rotation of the output pulley  72  with a quantity of torque transmitted between the pulleys. Although the pitch diameters of the pulleys are shown as equal in  FIG. 8 , it is understood that the ratio of the two pulley pitch diameters can be varied so as to alter the torque and rotational velocity transmitted between the pulleys. 
         [0032]    The cable assembly  28  can comprise any construction capable of transmitting only tensile force, only compressive force, or both tensile and compressive forces, while allowing sufficient flexure to accommodate relative motion between the gripper head and actuator. Ideally, the transmission of the tensile or compressive force though the cable assembly occurs with minimal or substantially no parasitic loss so that the majority of the force applied to the input pulley  70  of the cable assembly  28  is available at the output pulley  72  to move the jaws of the gripper. Such cable assemblies are used to control bicycle gear shifting mechanisms. 
         [0033]      FIG. 9  shows yet another alternative embodiment of the gripper. A gripper head  20  includes the gripping jaws and those components responsible for moving and guiding the jaws. A cover  22  is attached to the gripper head  20  with threaded fasteners  24 . A ferrule  26  is attached to the gripper cover  22  by adhesive bonding or other suitable means. An output end  30  of a cable assembly  28  passes though axially aligned holes in the ferrule  26  and in the cover  22  and is attached by threading into a lead screw  80 . A lead nut  82  is engaged by the lead screw  80  with the opposing end of the lead nut  82  attached by threading or other suitable means to the appropriate component within the gripper head  20  responsible for moving the gripper jaws. The opposing end of the ferrule  26  is threaded or adhesively bonded onto the distal end of a sheath  34  of the cable assembly  28  (see also  FIG. 3 ). The proximal end of the sheath  34  is threaded or adhesively bonded into the ferrule end of a motor housing  38 . An input end  32  of the cable assembly  28  passes through a hole in the motor housing  38  and is coupled into the shaft of an actuator  44 , shown here as a motor, to convert the rotation of the motor shaft into a corresponding rotation of the input end  32 , output end  30  and lead screw  80 . The rotation of the lead screw  80  is converted into a corresponding linear motion of the non-rotating lead nut  82  to move the gripper jaws. Threaded fasteners  46  attach the motor  44  to the motor housing  38 . 
         [0034]    The cable assembly  28  can include any construction capable of transmitting torque, while allowing sufficient flexure to accommodate relative motion between the gripper head  20  and actuator  44 . Ideally, the transmission of the torque though the cable assembly  28  occurs with minimal or substantially no parasitic loss so that the majority of the torque applied to the input end  32  of the cable assembly  28  is available at the output end  30  to move the jaws of the gripper. Such cable assemblies are used to control automotive speedometer mechanisms. 
         [0035]      FIGS. 10 ,  11 ,  12  and  13  show an alternative embodiment of a cable assembly  28 , which is suitable for the transmission of torque. A short length of the cable assembly  28  is shown for illustrative purposes and it is understood that the overall length of the assembly can be increased or decreased as desired. An input end  32  and an output end  30  bound a plurality of cylindrical couplings  90  interdisposed with a plurality of spherical couplings  92 , which are surrounded by a flexible sheath  34 . The cylindrical couplings  90  can possess a spherical cavity on each end of a cylindrical body. Each cavity is divided by a rectangular tab  94  with the center of the tab  94  located coincidently with the longitudinal axis of the cylinder. The longitudinal axis of each tab  94  is chosen to be orthogonal to that of the other tab  94 . The spherical couplings  92  possess a spherical radius complimentary to the radius on each end of the cylindrical couplings  90 . The spherical diameter of the spherical couplings  92  is interrupted by two rectangular slots  96 ,  98  with the center of each slot located coincidently with center of the spherical diameter. The longitudinal axis of each slot is chosen to be orthogonal to that of the other slot, with the width of the slots complimentary to the width of the tabs  94  of the cylindrical couplings  90 . The complimentary spherical radii and slot and tab widths allow alternating spherical and cylindrical couplings to nest and be nested by adjacent couplings with the tab of each cylindrical coupling  90  engaging the slot of mating spherical coupling  92  so that the column of couplings shares a common centerline. As the cable assembly  28  is laterally flexed, each coupling is free to rotate unencumbered about the center of its spherical radius parallel to the longitudinal axis of a slot or tab, while maintaining a common line of contact with an adjacent coupling. In this manner, the line of contact between each adjacent pair of couplings remains normal to the radius of curvature of the flexed sheath  34 . The engagement of slots  96 ,  98  and tabs  94  prevent rotation of one coupling around the line of contact with an adjoining coupling, allowing the transmission of torque between couplings along the line of contact. The input end  32  and output end  30  possess a spherical radius and complimentary slot on one end in an analogous manner to the spherical couplings  92 . The radius and slot on the end of the input end  32  allow the end to nest into the complimentary spherical cavity on the first cylindrical coupling on the proximal end of the cable assembly  28  and the radius and slot on the end of the output end  30  allow the output end to nest into the complimentary spherical cavity of the last cylindrical coupling on the distal end of the cable assembly. The completed cable assembly  28  is thusly able to transmit torque between the input end  32  and output end  30  along the longitudinal axis of the cable assembly  28 . 
         [0036]      FIG. 14  shows another embodiment of the invention. A gripper head  20  includes the gripping jaws  100  and those components responsible for moving and guiding the jaws. A cover  22  is attached to the gripper head  20  with threaded fasteners  24 . A ferrule is attached to the gripper cover  22  by adhesive bonding or other suitable means, including a clamping ferrule design that allows easy reduction of cable length in the field. The ferrule shown as components  26 A,  26 B, and  26 C is a clamping style ferrule. To minimize overall height of the assembly, the ferrule is shown located perpendicular to the gripper body. A cam assembly  106 ,  108 ,  110  within the cover  22  transfers the motion of a cable assembly  28  to a linear converter  104 . The cam  106 ,  108 ,  110  could be eliminated and the cable assembly  28  connected directly to the linear converter  104  if assembly height did not need to be minimized. An output end  30  of the cable assembly  28  passes through the ferrule  26 A,  26 B,  26 C and cover  22  and is attached either to the cam  106 ,  108 ,  110  or directly to the linear converter  104  within the gripper head  20 . The drawing shows a swaged end fitting on the cable but any suitable means of securing the cable may be used. A spring  102  is positioned to push directly on either the cam assembly  106 ,  108 ,  110  or on the linear converter  104 . This spring  102  provides positive driving force to the gripper jaws  100  and may be used to retain the gripper jaw position in the event that the cable assembly  28  should fail. The opposing end of the ferrule  26 A,  26 B,  26 C is suitably attached to the distal end of a sheath  34  of the cable assembly  28 . The proximal end of the sheath  34  is suitably attached into the ferrule end of a motor housing  38 . An input end  32  of the cable assembly  28  passes through a hole in the motor housing  38  and is coupled to the shaft of an actuator  44 , shown here as a motor, via a mechanism that converts the rotation of the motor shaft to a linear motion of an input end  32  and therefore, an output end  30 . The mechanism to convert the actuator rotary motion to linear motion may use any suitable means, including, but not limited to the rack and pinion; lead screw and lead nut; or pulley systems previously described. The motion of the output end  30  can be converted by a corresponding linear converter  104 , either through the cam assembly  106 ,  108 ,  110 , or directly as previously mentioned, to move the gripper jaws  100 . The motor housing  38  may also include provisions for mounting position sensors to infer the jaw  100  position based on the location of the end of the cable assembly  28 . This would be useful to eliminate the need for sensors on the gripper itself, or could be used in conjunction with sensors on the gripper to easily detect the failure of the cable assembly  28 . Threaded fasteners  46  attach the motor  44  to the motor housing  38 . The cable assembly  28  can be any construction capable of transmitting tension, while allowing sufficient flexure to accommodate relative motion between the gripper head  20  and motor  44 . Ideally, the transmission of the force though the cable assembly  28  occurs with minimal parasitic loss so that the majority of the force applied to the input end  32  of the cable assembly  28  is available at the output end  30  to move the jaws of the gripper. Such cable assemblies are used to control automotive carburetor throttle mechanisms. 
         [0037]    While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.