GRIPPING DEVICE WITH FLEXIBLE ELEMENTS
In the mechanics in general, it is often necessary to grasp firmly, with the same clamping tool, objects having different shape and dimension. The clamping tool with flexible elements, described in this patent, satisfies this need. This kind of tool can be used when it is needed to clamp a rigid or a deformable object. The pressure exerted by the clamping tool on the object can be easily changed, making the clamp suitable even for the manipulation of soft or delicate objects. The grip can be necessary to secure the object to the clamp or the clamp to the object. It will be described now the clamping tool referring specifically to the submarine robotics. It is needed to secure the clamping tool of the underwater rover to the structure on which operate (for example a pipeline). Usually, to obtain a firm grasp, it is used a clamping tool powered by hydraulic pistons as shown in figure 1. The frame 102 of the rover clamping tool in figure 1, is
anchored to the structure 101, using two clamps , figure 1, part 104 and 105. Each clamp can rotate around a pin 106 and 107 and is powered by a hydraulic piston 108 and 109. The cradle 103 of the rover is in contact with the underwater structure. Each clamp exerts a local force against the external surface of the structure. This solution presents the advantage to be easy and robust, but has the disadvantage to be not general. Each time it is needed to clamp a structure having a different diameter, the geometry of the clamps has to be reconfigured; this set-up is necessary because each piston, while the clamping tool is closed, must form 90 degrees with its clamp to transmit the overall hydraulic torque around the pin. The clamps have to satisfy the following constraints; they don't have to touch each over (they are complanate), they must touch the object in suitable points to guarantee a good grasp. The same clamping tool with clamps can clamp only a limited range of different sizes. For example, to secure a rover on structures having a diameter from 8 to 36 inches, it is necessary to own a set of at least 5 or 6 different clamping tools. Before of the diving, known "a priori" the diameter of the structure to clamp, it is necessary to equip the rover with the relative clamping tool. The clamping tool with flexible elements described in this patent, is able to replace the whole clamping set of clamping tools with traditional clamps; the same clamping tool with flexible elements can grasp for example, structures from 0 inches to 36 inches. Using a classic clamping tool, it is necessary to know the shape and the dimension of the object to grasp; for example, the two arms of the nutcracker are shaped to host the nut (and cannot grasp an hazel-nut). During the grasping there is a sort of recognition shape object to grasp/shape of the clamp. The lasso works using a different principle.
Once the lasso is positioned around the object to clamp, the lasso rope is taut. It is the rope of the lasso that, thanks to its deformability, is able to copy faithfully the contour of the object. The clamping tool with flexible elements has a structure similar to the clamping tool with clamps and a principle similar to the lasso. It is now described a clamping tool with three flexible elements as shown in figure 2 and 3. Three clamps 204 and 205, and 301, 302 and 303, are linked to a frame part 202, provided with a cradle 203; each clamp can rotate around a pin 206 and 207. A flexible element 210 and 211, and 304, 305 and 306 is linked to the free extremity of each flexible element. The three flexible elements are tensioned by one ore more winches 212 positioned inside the frame. A pin 213 forces the flexible elements to be in strict contact with the element to grasp 201. As shown from the side view in figure 3, the flexible elements are located on different planes 304, 305 and 306; Each flexible element exerts on the object a pressure. In the case of the clamping tool with clamps, the cradle generates on the object forces equal and opposite to the resultant of the forces exerted by the clamps on the object; in the case of the clamping tool with flexible elements, the cradle creates on the object forces equal and opposite to the resultant of the forces generated by the flexible elements and by the clamps on the object. The winch (or winches) has the task to tighten the flexible elements and than to close the clamp around the object; the opening of each clamp is acted by a spring as shown in figure 2, part 208 and 209. The figure 2 shows the working principle of the clamping tool; the real position of one of the release springs is shown in the figure 3, part 307). It is now described the grasping procedure of the clamping tool with flexible elements as shown in figure 4, 5 and 6. While the clamps are
parallel each over as shown in figure 4 and perpendicular to the cradle, the clamping tool is brought near to the object to grasp till the object gets in proximity or contact of the cradle as shown in figure 5. Then the winch (or winches) is powered; the torque of the winch (or winches) is used, initially to close the clamps, after to secure the grasp as shown in figure 6. The torque exerted by the winch (or winches) determines the grasping force. The clamping tool with flexible elements has a working principle similar to the lasso; the flexible element, during the movement of the closure of the clamping tool, creates a sort of circle that tightens until it finds the profile of the object as shown in figure 7 and 8. The synchronised movement clamps/flexible elements, positions the object in close contact with the cradle, and centres the object respect to the cradle. While for the clamping tool with clamps as shown in figure 1, the grasp clamping tool/object is performed by a limited number of contact points, the grasp flexible elements/object as shown in figure 2 and 3 is exerted along the whole profile of the object. A distributed grasp is more delicate than a single points grasp; on the object are applied not local forces but is applied a pressure. Each clamp with flexible elements can grasp objects having a maximum size; it is possible, for example, to build a clamp with flexible elements able to grasp structures from 0 to 30 inches. Depending on the kind of application, it is inconvenient to use a clamp larger than 30 inches to grasp structures for example of 4 inches. To solve this problem, it has been designed a clamping tool with flexible elements having a variable width as shown in figure 9 and 10. The parts of the frame that sustain the clamps, part 901 and 902, are mounted on sliding guides 903 and 904. A system of fast fastening 905 and 906
allows to regulate manually the width of the clamping tool. The width of the clamping tool with flexibb elements and variable width is decreased when there are problems of clearance, to increase the clamp handiness and for the transport. For example, it is possible to use a clamping tool with flexible elements and variable width, to execute submarine cuts with diamond wire as shown in, figure 11 and 12. This application admits a dependence with the industrial patent WO02075059 "Method and apparatus for cutting underwater structures" of Matteucci Francesco, of the company TS tecnospamec Sri (It). Once the cutting machine is secured to the structure to cut as shown in figure 11, part 1101, the structure is cut using a diamond wire as shown in figure 5, part 1102 that rotates around pulleys as shown in figure 5, part 1103, 1104 and 1105. One or more pulleys are powered. All the pulleys are mounted on sliding guides (not shown in the picture); during the cut, the diamond wire is slowly brought on the object to cut. To have a more detailed description of the cutting process, it is advisable to consult the patent VvO02075059. The clamping tool with flexible elements, thanks to its easy architecture and clamping capabilities, can be used in several fields; not limitative examples are the industry, the robotics, the building, the medicine etc. More specific fields of application are; lifting with cranes, underwater operations, micromanipulators, surgical operations.