Abstract:
A gripper includes a body, an actuator movably supported by the body and a first hub rotatably supported by the body where the first hub rotates about a transverse axis. The gripper also includes a drive arm having a camming surface. The drive arm is coupled to the first hub so as to be rotatable about the transverse axis. A member drivingly interconnects the camming surface and the actuator such that an arm coupled to the first hub operably moves in response to the actuator.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    The present invention relates to a gripper for grasping objects and, more particularly, to a sealed gripper for holding work pieces in adverse environments.  
           [0002]    Grippers are commonly used in conjunction with robots in industrial applications for picking, placing and fixturing work pieces during the various steps of manufacturing a final component. Typical grippers include pneumatically or hydraulically actuated cylinders, which cause one or more arms to move through a desired range of motion to grasp a work piece.  
           [0003]    Unfortunately, when a mechanism such as a gripper is to be sealed to prevent ingress of contamination, one or more design features are often compromised. Specifically, a sealed mechanism is usually much larger than its unsealed counterpart due to the requirements of internal levers, cams and seals. Additionally, in the case of the gripper, it is often difficult to seal rotating hubs without increasing the size of the overall packaging envelope.  
           [0004]    In accordance with the present invention, a gripper includes a body, an actuator movably supported by the body, and a first hub rotatably supported by the body where the first hub rotates about a transverse axis. The gripper also includes a drive arm having a camming surface. The drive arm is coupled to the first hub so as to be rotatable about the transverse axis. A member drivingly interconnects the camming surface and the actuator such that an arm coupled to the first hub operably moves in response to the actuator.  
           [0005]    Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates and from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a perspective view of a sealed gripper showing a preferred embodiment of the gripper with gripper arms in a fully closed position;  
         [0007]    [0007]FIG. 2 is an exploded perspective view of the sealed gripper constructed in accordance with the teachings of the present invention;  
         [0008]    [0008]FIG. 3 is a cross-sectional top view of the preferred embodiment sealed gripper taken along line  3 - 3  of FIG. 1;  
         [0009]    [0009]FIG. 4 is a cross-sectional side view of the sealed gripper of the present invention taken along line  4 - 4  of FIG. 3;  
         [0010]    [0010]FIG. 5 is a cross-sectional side view showing the preferred embodiment of the gripper with gripper arms in a fully opened position; and  
         [0011]    [0011]FIG. 6 is a cross-sectional end view of the gripper of the present invention taken along line  6 - 6  of FIG. 4. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]    With reference to FIG. 1, a sealed gripper constructed in accordance with the teachings of the present invention is generally identified at reference numeral  10 . The sealed gripper  10  includes a body  12  defining a longitudinal axis  14  and an actuator mechanism  16  for rotating an inner arm  18  relative to an outer arm  20  about a transverse axis  22 . The inner arm  18  and the outer arm  20  are positioned in FIG. 1 corresponding to a fully closed position. FIG. 5 depicts sealed gripper  10  of the present invention having inner arm  18  rotated about transverse axis  22  to a fully opened position.  
         [0013]    As shown in FIGS. 2 and 3, sealed gripper  10  further includes a removable end cap  24  that defines a sealed cylindrical chamber  26  aligned with longitudinal axis  14 . End cap  24  is preferably threadingly engaged to body  12 . Additionally, an O-ring  27  provides a seal between end cap  24  and body  12 .  
         [0014]    Body  12  includes a cylindrical bore  28  extending along longitudinal axis  14  interconnecting chamber  26  with an actuating chamber  30 . Actuating chamber  30  includes a cylindrical wall portion  32  and a pair of counter bores  34  located at each end of wall portion  32 . A stop face  35  defines the end of each counter bore  34 . Each of wall portions  32  is coaxially aligned with transverse axis  22 .  
         [0015]    Actuator mechanism  16  includes a piston  36  slidingly disposed within cylindrical chamber  26  for powered movement along longitudinal axis  14 . Movement of piston  36  in an advancing or “arm opening” direction is caused by a supply of pneumatic fluid under pressure entering cylinder chamber  26  via a port  37  positioned in end cap  24 . Similarly, movement of piston  36  in an opposite or “arm clamping” direction is caused by supplying pressurized fluid through a port  38  positioned in body  12 . A seal  40  is disposed within a circumferential groove  42  to restrict the pressurized fluid from passing between piston  36  and body  12 .  
         [0016]    Actuator mechanism  16  further includes a slide  44  having a piston rod  46  and a clevis  48 . Piston rod  46  is disposed and reciprocally slidable in bore  28 . A seal  49  prevents pressurized fluid from passing between piston rod  46  and body  12 . Clevis  48  includes a pair of bifurcated legs  50  extending generally parallel to, but offset from, longitudinal axis  14 . Each of legs  50  includes an elongated slot  52  and an aperture  54  extending therethrough. Piston rod  46  is coupled to piston  36  via a threaded fastener  56  for a coincidental longitudinal and linear movement.  
         [0017]    A roller assembly  58  includes an inner roller  60  and two outer rollers  62 , all of which are journaled about a roller pin  64 . A thrust washer  66  is disposed between each adjacent pair of rollers. A pair of snap rings  67  are snapped onto the laterally outboard ends of roller pin  64  for retaining the roller pin within apertures  54  of slide  44 . Rollers  60  and  62  are preferably constructed from 6150 hot rolled steel, then hardened and ground to a Rockwell C hardness of 54-58.  
         [0018]    With reference to FIGS. 3, 4 and  6 , a pair of cam roller plates  68  are positioned within actuating chamber  30  substantially parallel to one another and offset from longitudinal axis  14 . Each of cam roller plates  68  includes a roller surface  70 , a hub relief  72  and a pair of apertures  74 . A pair of generally cylindrical pins  76  are disposed within apertures  74  and corresponding apertures  78  located within body  12  to appropriately position and fix cam roller plate  68  relative to the body. Each of cam roller plates  68  is preferably constructed from 4140 hot rolled steel.  
         [0019]    A drive arm  80  is formed from a substantially flat plate and includes a first finger  82  offset from a second finger  84 . A camming surface  86  is defined by first finger  82  and second finger  84 . As best shown in FIGS. 4 and 5, camming surface  86  includes an arcuate portion  88 , a tapered flat portion  90  and a stepped or indented flat portion  92 . Second finger  84  includes an aperture  94  aligned with transverse axis  22 . Second finger  84  also includes a plurality of apertures  96  positioned circumferentially about and extending parallel to transverse axis  22 .  
         [0020]    A first hub  98  includes a generally circular cylindrical first portion  100  integrally formed with and axially aligned with a drive shank or second portion  102 . First hub  98  is disposed within actuating chamber  30  and generally supported by cylindrical wall  32  for rotational movement about transverse axis  22 . First hub  98  also includes a central aperture  106  extending along transverse axis  22 . A plurality of apertures  108  are circumferentially positioned about transverse axis  22  extending generally parallel thereto. A seal  110  is compressed between first hub  98  and stop face  35 .  
         [0021]    A second hub  112  is substantially the mirror image of first hub  98  having a first portion  114 , a second portion  116 , a central aperture  118  and a plurality of circumferentially positioned apertures  120 . Second hub  112  is also circumferentially supported by cylindrical wall  32  for rotation of movement about transverse axis  22 .  
         [0022]    As best shown in FIG. 2, outer arm  20  includes a proximal end having a plurality of apertures  132 . An aperture  134  is positioned at the distal end of outer arm  20  to provide a coupling pivot point for a gripper pad (not shown). A threaded fastener  136  along with two dowel pins  138  fixedly mount outer arm  20  to body  12 . Inner arm  18  includes a central aperture  126  and a plurality of circumferentially spaced apertures  128  positioned at its proximal end. At the distal end, an aperture  130  is provided to facilitate interconnection with a gripper pad (not shown). Dowel pins  140  drivingly interconnect inner arm  18 , first hub  98 , drive arm  80  and second hub  112 . A hub cab  142  is also drivingly coupled to the aforementioned components via dowel pins  140 . A threaded fastener  144  cooperates with a nut  146  to retain first hub  98  and second hub  112  within actuating chamber  30 . Elastomeric seals  147  further prevent contaminants from entering actuating chamber  30  around fastener  144 . A front cover  148  encloses actuating chamber  30 . A gasket  150  and threaded fasteners  152  sealingly couple front cover  148  to body  12 .  
         [0023]    A proximity sensor  154  is coupled to body  12  proximate slot  52  of slide  50 . Proximity sensor  154  operates to output a first signal  156  indicative of piston  36  being in the fully retracted position shown in FIGS. 3 and 4. Proximity sensor  154  also operates to output a second signal  158  when piston  36  and slide  50  are positioned in the fully extended, arms open, position shown in FIG. 5. A removable cover plate  159  is coupled to body  12  at an alternate proximity sensor location on the opposite side of body  12 . It should be appreciated that proximity sensor  154 , first arm  18  and second arm  20  may be positioned on either side of body  12  to provide mounting versatility of sealed gripper  10  in the work place. Body  12  also includes orthogonally oriented mounting flats  160  for coupling the body to a suitable fixture. A cylindrical surface  161  is formed on body  12  to provide further mounting flexibility for sealed gripper  10 .  
         [0024]    With reference to FIGS.  4 - 6 , the operation of rotatable inner arm  18  in response to linear travel of slide  44  can be explained. Pressurized fluid entering port  37  causes piston  36  to translate along longitudinal axis  14 . Because slide  50  is mechanically coupled to piston  36 , the slide also translates along axis  14 . Outer rollers  62  rotate about roller pin  64  as each outer roller contacts a corresponding roller surface  70  of cam roller plate  68 .  
         [0025]    Inner roller  60  is drivingly engaged with drive arm  80 . Specifically, inner roller  60  engages camming surface  86  to induce a rotational moment about transverse axis  22 . Because drive arm  80  is pinned to first hub  98 , second hub  118  and inner arm  18 , rotation of drive arm  80  directly corresponds to rotation of inner arm  18 . Inner arm  18  reaches the fully opened arm position depicted in FIG. 5 once piston  36  bottoms within cylindrical bore  28 .  
         [0026]    To cause inner arm  18  to rotate in the clamping direction, pressurized fluid is input to port  38 . The pressurized fluid acts upon piston  36  causing the piston and slide  44  to translate in the opposite direction along longitudinal axis  14 . Inner roller  60  imparts a rotational moment to drive arm  80  as it passes through arcuate portion  88 . A self-locking condition is achieved as the rollers are wedged between tapered flat portion  90  and roller surfaces  70 . Preferably, tapered flat portion  90  is constructed at a five-degree angle to longitudinal axis  14  to provide a mechanical wedging effect. Indented flat portion  92  provides a detent to retain center roller  60  in position. One skilled in the art will appreciate that it is advantageous to lock inner arm  18  relative to outer arm  20  when in the clamped position shown in FIG. 4. Once center roller  60  is in contact with indented flat portion  92 , arm  18  will remain in its clamped position without the presence of pressurized fluid at port  38 . Thus, operators of sealed gripper  10  need not be concerned with tools or components unexpectedly becoming unclamped if a loss of pressure should occur.  
         [0027]    A release mechanism  162  is slidingly disposed within an aperture  164  formed within end cap  24 . Release mechanism  162  includes a driver  166  threadingly engaged with a fastener  168 . A seal  170  is disposed within a groove  172  formed in aperture  164 . When arm  18  is in the clamped position shown in FIG. 4, piston  36  is at the fully retracted position adjacent end cap  24 . At this time, fastener  56  is aligned with and positioned proximate to driver  166 . End cap  24  is constructed to assure that piston  36  may fully return and contact end cap  24  prior to bottoming on driver  166 . To unlock center roller  60  from indented flat portion  92 , a force is applied to fastener  168  to transfer load from driver  166  to fastener  56 . A mallet may be used to provide the necessary force. Once center roller  60  is within tapered flat portion  90 , fluid pressure entering port  37  causes arm  18  to rotate toward the opened position.  
         [0028]    Therefore, it should be appreciated that the configuration and operation of the sealed gripper provides manufacturing and operational advantages over the prior art. Specifically, the present invention provides a sealed gripper suited for application in contaminated environments. Additionally, the assembly of an actuator, slide, drive arm, and hub arrangement allows for compact packaging and reduced mechanical movement of components.  
         [0029]    The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without department from the spirit and scope of the invention as defined in the following claims.