Patent Publication Number: US-6220641-B1

Title: Cradle and pressure grippers

Description:
U.S. GOVERNMENT RIGHTS 
     The United States Government has rights in this invention pursuant to Contract No. DE-AC07-81NE44139 between the U.S. Department of Energy and West Valley Nuclear Services Company. 
    
    
     BACKGROUND OF THE INVENTION 
     This apparatus is an improvement upon lifting devices such as supporting, gripping and pressure tongs used in manufacturing, demolition and material handling. Generally, lifting devices of these types are designed for a particular function or designed to lift a particular size and shape. The gripper described here is designed to incorporate the function of gripping, supporting, and pressure tongs in one device and may lift and support objects of varying size and shape. Shapes that may be lifted by the grippers include bars, pipes, tubes, T-shapes, angles, I-beams, and plates. 
     Supporting tongs are known and used to support objects of a particular configuration. The objects lifted and supported by supporting tongs are required to have clearance at the base of the object to allow space for the feet of the tong or gripper to contact the bottom of the object. Supporting tongs have opposing arms that are not intended to close completely together because they are designed to lift objects of a known and constant size. The gripper described here uses fingers with inclined tips that taper and act as a wedge to facilitate lifting objects directly off the floor and into the center of the device. The gripper is designed to allow complete closure of the opposing finger sections and may slightly over close allowing flexibility to lift variously sized and shaped objects. The wedge shape and inclined fingers allow the gripper to pick up objects that do not have the clearance required for use of supporting tongs. 
     Pressure tongs grip the vertical sides of an object, such as boxes, ingots or other right-sided objects, and apply friction to allow lifting of the object. Once objects have been lifted by the fingers of the gripper described here and the object is in or near the center of the gripper, a moveable arm squeezes the vertical sides together applying the friction required to lift the object similar to the only function of pressure tongs. 
     Gripping tongs, used to lift round or cylindrical objects, grip the object around the circumference with the tongs extending below the center of the object with the tongs generally in continuous contact with the rounded surface of the object. Like supporting tongs, gripping tongs have opposing arms that are not intended to close completely together. In the case of gripping tongs, they are designed to lift objects of a size range varying by about 25% and the tongs will extend just below the center of the of the object and are not designed to completely envelop the cylindrical or round object. If round or cylindrical items are to be lifted, the gripper described here supports the item below the center of the item in cradle-like hold. The gripper described here may not continuously contact the surface of round or cylindrical items, but will completely envelop the object. 
     The gripper provides an attachment point for a crane hook and is used for lifting, grasping, and/or supporting various structures and structural shapes in random positions. The gripping tool has two opposing finger sections. One finger section is stationary and has four individual fingers, the other finger section is moveable and has three individual fingers. There is space between the fingers of each section to allow the opposing sections to interlock. The opposing finger sections may close together allowing the inclined, tapered tips to extend beyond the plane defined by the opposing finger section&#39;s engagement surface. Thus, the interlocking fingers enable the gripper to lift and support objects of varying sizes. The interlocking fingers are more likely to bend, rather that crush or shear the lifted object if the gripper is closed too tightly. The ability to bend rather than crush or shear the object being lifted serves to decrease the amount of material that may become permanently damaged, especially thin wall tubing, if the gripper is inadvertently over-closed. Materials that become bent are more easily returned to their intended shape as compared to materials that become crushed or sheared. 
     Gripping tools currently known in the art to have interlocking or inter-fitting components do not allow the opposing components to close beyond the boundary defined by the opposing section because one jaw will confront the engagement surface of the opposing jaw. Examples of these types of tools are in U.S. Pat. Nos. 4,199,972 and 4,283,933 issued to Weiner. 
     Gripping tools currently known to have one moveable and one stationary arm are used to open and close tightly sealed containers. These tools do not have lifting bails or interlocking fingers that can extend beyond the engagement surface of the opposing arm. An example is in U.S. Pat. No. 3,862,776 issued to Sims and Borello. 
     The gripper may provide significant cost savings for manufacturing, demolition and material handling operations because this one device can lift and support objects of varying size and shape and thereby may eliminate the need to design supporting, gripping or pressure tongs to perform each particular function. Additional cost savings may result from the gripper&#39;s tendency to bend rather than crush or shear objects if the gripper is over-closed around the object. 
     OBJECTS OF THE INVENTION 
     The primary object of this invention is to incorporate the functions of supporting, gripping and pressure tongs into a single device. 
     Another object of this invention is to provide a lifting device that is capable of lifting, supporting and gripping objects of varying size and shape. 
     Another object of this invention is to provide lifting, supporting and gripping without permanent damage to the items being lifted, supported or gripped. 
     SUMMARY OF THE INVENTION 
     A gripper designed to incorporate the functions of gripping, supporting and pressure tongs into one device. The gripper is capable of lifting and supporting objects of varying size and shape. This one device can lift and support bars, pipes, tubes, T-shapes, angles, I-beams and plates. 
     The gripper uses two opposing finger sections with interlocking fingers that incline and taper to form a wedge. Power is provided to a moveable finger section by an actuating device to close the finger sections around an object to be lifted. A lifting bail on the gripper may be attached to a crane to provide for vertical lifting. 
     The interlocking fingers allow the flexibility required to lift and support objects of varying size and shape and will bend, rather than crush or shear, the object if the gripper is inadvertently over-closed around the object to be lifted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation the invention. 
     FIG. 1 a  is a partial side elevation of the gripper in a closed position. 
     FIG. 1 b  is a partial side elevation of the gripper in an open position. 
     FIG. 2 is a front elevation. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1,  1   a,    1   b,  and  2  depict the preferred embodiment of the gripper  10 . A stationary finger section  20  has four individual fingers  23 . Each finger  23  is 10.5 inches long and has a horizontal tip  21  5.5 inches long that tapers at a 6° incline to form a wedge. The outside dimensions of the stationary finger section are 16.5 inches long by 6.63 inches deep by 6.0 inches wide. 
     The moveable finger section  22  has three individual fingers, the outside fingers  25  of the moveable section  22  are both 0.63 inches wide, the central finger  27  of the moveable finger section  22  is 0.75 inches wide. Each of the three fingers  25  and  27  are 12.06 inches in length. The outside dimensions of the moveable finger section are 16.5 inches long by 9.0 inches deep by 4 inches wide. The horizontal tip  21  portion of the fingers  23  and  25 , like the tips  21  of the stationary section, is 5.5 inches long that tapers at a 6° incline to form a wedge. 
     The vertical component of the fingers  23  on the stationary finger section  20  are offset relative to the fingers  25  and  27  of the opposing moveable finger section  22  to allow the fingers  23  of the stationary finger section  20  to interlock with the fingers  25  and  27  of the moveable finger section  22  when the finger sections  20  and  22  move toward each other. 
     Two support bars  29  are attached to each finger  23  of the stationary finger section  20  and serve to maintain constant inter-spacing between the fingers  23  of the stationary finger section  20 . The support bars  29  add rigidity to the stationary finger section  20  and prevent the fingers  23  from becoming mal-aligned and inhibiting smooth operation of the gripper  10 . 
     The stationary finger section  20  has a clearance hole through which a pivot pin  24  is placed. The moveable finger section  22  has a slot  26  that allows the moveable finger section  22  to move relative to the pivot pin  24 . A range of motion of the moveable finger section  22  relative to the stationary finger section  20  is defined by a relationship between the pivot pin  24  and the slot  26  in the moveable finger section  22 . The range of motion of the gripper  10  is such that the moveable finger section  22  passes between the fingers  23  of the stationary finger section  20  to close. As depicted in FIG. 1 a,  the opposing finger sections  20  and  22  may close together allowing the inclined, tapered tips to extend beyond the plane defined by the opposing finger section&#39;s engagement surface. The engagement surface is defined as the surface of the fingers  23 ,  25 , and  27  that contacts the workpiece  60 . The inclined, tapered fingers  23 ,  25  and  27 , combined with the interlocking and over-extending finger sections  20  and  22  allow the gripper  10  to grab, support and lift work pieces  60  of varying size and shape. 
     An actuating device  30  is powered by an alternating current power supply (not shown) via a power cord  34 . The actuating device  30  used in the preferred embodiment is a modified Curtis-Wright P-16 Power Hawk Rescue Tool. The actuating device  30  is mounted on a support frame  50  and provides power to the moveable finger section  22  to rotate in a range of motion allowed by the pivot pin  24  and slot  26  to close around a workpiece  60 . The actuating device  30  is coupled to said finger sections  20  and  22  by two sets of two quick release pins  32 . One set of quick release pins  32  on either side of the actuating device  30 . The moveable finger section  22  engages a rotational element  36  of the actuating device  30 , such as a gear, to provide rotation to the moveable finger section  22  in the range of motion allowed by the pivot pin  24 . The stationary finger section  20  is held in place, and rendered immoveable, by the quick release pins  32  that secure the finger sections  20  and  22  to the actuating device  30 . If the quick release pins  32  are removed from the gripper  10  the finger sections  20  and  22  will remain secured to the support frame  50  by the pivot pin  24 . 
     A support frame  50  is attached to the pivot pin  24  exterior to the stationary finger section  20  and held laterally in place by cotter pins  28  through small holes in the both ends of the pivot pin  24 . A lifting bail  40  is attached by bolts  51  to the opposite end of the support frame  50  at the pivot pin  24 . The lifting bail  40  provides a point of attachment for a crane hook (not shown). The crane (not shown) provides lift for the entire gripper  10 . The gripper  10  weighs about 100 pounds and has a safe working load of about 2000 pounds.