Abstract:
An effector comprises a pair of opposing jaws directly mounted on a keeper so that the jaws are pivotable about the keeper. The jaws are connected to an actuating member within the keeper, so that translational movement of the actuating member causes the jaws between an open and closed position.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an effector and to a tool, and particularly, but not exclusively to a surgical tool and an effector therefor. 
     A known form of surgical tool has an effector mounted at the end of a shaft. The effector has two jaws and is actuated by an actuating member in the shaft. The jaws are pivotally attached to one another scissor fashion by means of a pin joint. The pivotal end of each jaw is attached to a respective ink by a further pin joint. The links attached to the jaws are attached to one another and to the actuating member in the shaft by means of a still further pin joint. Translational movement of the actuating member in the shaft causes the links to move in a scissor-like manner so that the jaws open and close. When the jaws are closed, the jaws, links and actuating member are aligned, axially of the shaft. However, when the jaws are fully open the links and the pivotal ends of the jaws project laterally beyond the diameter of the shaft. 
     This lateral projection of the links and jaws beyond the diameter of the shaft is undesirable since the tissue of the patient may be caught in the links and jaws of the tool. Furthermore, the pins of the pin joints are very small, so that it is difficult to install the pins securely. The small size of the pins also means that they are very prone to fracture. Again, such fractures are obviously undesirable since they result in the introduction of foreign material into the patient. The mechanical advantage of the tool also varies according to the position of the jaws. As the jaws approach the closed position, the mechanical advantage of the system is greatly reduced in comparison with the mechanical advantage when the jaws are in the fully open position. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a tool in which the above disadvantages are overcome. 
     The invention provides an effector as claimed in claim  1  and a tool as claimed in claim  17 . 
     An embodiment of the invention will now be described with reference to the drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an exploded perspective view of a tool in accordance with the invention; 
     FIG. 2 shows a perspective view of one half of the effector of the tool of FIG. 1 in a closed position; 
     FIG. 3 shows a perspective view of one half of the effector of the tool of FIG. 1 in an open position; 
     FIG. 4 shows the tool of FIG. 1 in the closed position; and 
     FIG. 5 shows the tool of FIG. 1 in the open position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, a surgical tool  1  has an effector  2 , a pull rod  3  and a tube  4 . The effector  2  comprises a pair of jaws  5   a ,  5   b , a keeper  6  and an actuating member  7 . The keeper  6  is divided along a plane of separation of the jaws  5   a ,  5   b  A—A to form two identical keeper parts,  6   a  and  6   b . The effector  2  is rotationally symmetrical about the plane of separation of the jaws A—A. Each jaw  5   a ,  5   b  is associated with a respective keeper part  6   a  or  6   b . The jaw  5   a  has an operational portion  8  which is used to carry out surgical procedures and an actuating portion  9 , where the movement of the jaw is controlled. The outer surface of the operational portion  8  of the jaw  5   a  is smooth, while the inner surface of the jaw  5   a  may be serrated or uneven. The lower surface of the actuating portion  9  has pivoting means in the form of a notch  10  engageable with pivoting means in the form of a corresponding rib  11  on the keeper part  6   a  so that the jaw  5   a  may be pivoted about the rib  11  on the keeper part  6   a . The rib  11  is arranged on the inner surface of the keeper part  6   a . The notch  10  and the rib  11  are arcuate to facilitate pivotal motion of the jaw  5   a  about the keeper part  6   a.    
     The actuating member  7  has an arm  12   a  projecting from its lower end in the direction of translational movement of the actuating member  7  and an actuating arm  12   b  projecting from its upper end, also in the direction of translational movement of the actuating member  7 . Projections  13   a  and  13   b  are located at the end of the respective arms  12   a  and  12   b , so that the arms  12   a  and  12   b  are slidable within a recess (see below) in the keeper parts  6   a  and  6   b  respectively and the actuating member  7  may thus be located in the keeper parts  6   a  and  6   b . The projections  13   a  and  13   b  also permit engagement of the respective jaws  5   b  and  5   a , so that the actuating member  7  can actuate the jaws  5   a  and  5   b.    
     The jaw  5   a  has actuating means, arranged on an opposite side of the plane of separation of the jaws A—A to the jaw pivoting means, in the form of a recess  14  on the upper surface of the actuating portion  9 . The recess  14  is engageable with actuating means in the form of the projection  13   b  on the actuating member  7  so that the jaw  5   a  may be actuated by the actuating member  7 . The recess  14  and the projection  13   b  are arcuate in cross-section to permit pivotal motion of the jaw  5   a  around about the projection  13   b . The keeper part  6   a  has a recess  15  adjacent the rib  11  for clearance of the projection  13   a  on the arm  12   a  of the actuating member  7  in the keeper part  6   a . When the actuating member  7  is inserted in the keeper part  6   b , the projection  13   b  engages in the recess  14  so that the top surface of the projection  13   b  is flush with the top surface of the actuating portion  9 . 
     The pull rod  3  is also attached to the actuating member  7  so that the pull rod  3  may actuate the actuating member  7 . The actuating member  7  may have a threaded bore and the pull rod  3  may be threaded so that the pull rod  3  and actuating member  7  can be connected together by means of the interengaging threads. Alternatively, the actuating member  7  may be moulded around serrations adjacent the end of the pull rod  3 . 
     FIGS. 2 and 3 show the actuating member  7  arranged in the keeper part  6   a . The jaw  5   a  is also arranged on the keeper part  6   a . The opposing jaw  5   b  (not shown) is arranged on the keeper part  6   b  in a similar manner. The actuating portion  9  of the jaw  5   a  is laterally offset from the actuating portion of the jaw  5   b  so that the actuating portions of the jaws  5   a  and  5   b  are located side by side in the keeper  6 . When the jaws  5   a ,  5   b , the actuating member  7  and the pull rod  3  are assembled in the keeper  6 , the tube  4  is: slid over the keeper  6  to hold the assembly together and constrain radial movement of the components in the keeper  6 . It is also desirable to constrain axial movement of the assembled components. The keeper parts  6   a  and  6   b  illustrated in the embodiment shown in FIGS. 1 to  3  have a groove  16  around their outer surface. When the tube  4  has been placed over the assembled components, the tube may be deformed around the groove  16  so that axial movement of the assembled components may be constrained. Alternatively, the outer surface of the keeper  6  may simply be bonded to the inner surface of the tube  4  to constrain axial movement of the keeper. It is also possible to include a resilient element on the keeper  6 , for example, a pip or spring-loaded ball catch which engages a through hole in the tube  4 , or vice versa, to constrain axial movement of the assembled components. 
     FIG. 2 shows one half of the assembly when the jaw  5   a  is in a closed position. In the closed position the pull rod  3  and actuating member  7  are in a retracted position. The jaw  5   a  rests on the rib  11  so that the jaw extends substantially parallel to the plane of separation of the jaws A—A. When the pull rod  3  is actuated so that it and the actuating member  7  move translationally within the keeper part  6   a  towards the jaw  5   a , the projection  13   b  on the actuating member  7  pushes the jaw  5   a , causing it to pivot about the rib  11  in a clockwise direction so that the jaw  5   a  opens (see FIG.  3 ). The pull rod  3  may be actuated by a variety of means, for example, by means of the actuator disclosed in UK patent application No. 9902647.8. It will be appreciated that the opposing jaw  5   b  (not shown) is pivoted in a similar manner in an anti-clockwise direction. The jaws  5   a  and  5   b  can be closed again by actuating the pull rod  3  and thus the actuating member  7  in the opposite direction so that they return to the retracted position. 
     FIGS. 4 and 5 show respectively the position of the jaws  5  in the open and closed positions. It will be seen that even in the open position there are no components, with the exception of the jaws  5   a  and  5   b  themselves, protruding beyond the diameter of the tube  4 , and the outer surface of the jaws is smooth. The risk of the tool catching on tissue of the patient is, therefore, minimised. 
     It will also be seen that the components are arranged in the tube  4  in such a way that it is very difficult for fluids and other matter to enter the tube  4 . Although the tool of the present embodiment is designed to be disposable, it may also be used as a re-usable tool. 
     It is thus desirable for the fluids and other matter entering the tube  4  to be kept to a minimum to aid re-sterilisation. 
     The mechanical advantage of the tool is substantially constant over the range of movement of the jaws. The fact that the recess  14  and notch  10  are located on opposite sides of the plane of separation of the jaws means that the mechanical advantage of the tool is also maximised. 
     The components of the tool may be made of a variety of materials. For example, the tube may be made of stainless steel or titanium alloy, whereas the jaws may be made of plastics or metal. 
     Different jaws may be used for different applications. For example the jaws may be forceps, where gripping is required. However, the jaws may also be scissors or spreaders respectively where cutting and spreading is required. Although the tool has been described in the context of surgical use, it will be appreciated that the tool may be used in many other fields where delicate handling of materials is required, for example in the electronics industry, botany or entomology.