Patent Publication Number: US-2011056334-A1

Title: Dynamometric tool with removable head

Description:
TECHNICAL FIELD 
     This invention relates to the field of medical equipment and relates to a dynamometric tool of longitudinal axis AA, capable of providing a tightening torque comprising:
         a head provided with a first housing arranged along the longitudinal axis and a second circular housing arranged along a transverse axis, perpendicular to the longitudinal axis, the head being designed to receive a dowel in the second housing;   a sleeve designed to be placed in the first housing, the sleeve being adapted to assume a working position wherein a first one of the ends thereof is located in the second housing for engaging with the dowel.       

     Such a tool is particularly used in surgery as a wrench, usually called sextant wrench, particularly in the dental field for implants. 
     STATE OF THE ART 
     Sextant wrenches are well known by the skilled person in the art and are widely used for the application of tightening torques. Some models are equipped with torque limiters and/or indicators designed to give a numerical value to the user during the tightening step. 
     Generally, this type of wrench consists of a head where a tightening dowel and a sleeve are housed, the latter working with the dowel during the tightening step. These wrenches may comprise a spring which acts on the sleeve end position when rotating the wrench in the opposite direction of tightening. 
     The main drawback of the known systems is that, once positioned, the sleeve is not partially, or not at all, removable from the head of the device, thereby making it difficult to clean the set, which is particularly important in the medical field. 
     Moreover, the tightening dowel must be easily removable and replaceable. However, in the tools of the prior art, it is not blocked satisfactorily according to the transverse axis when the sleeve is engaged in the head and may therefore be induced to drop from the device that is being used. 
     This invention proposes to provide a dynamometric tool free of the above drawbacks. It is particularly advantageous in an application as a sextant wrench. 
     DISCLOSURE OF THE INVENTION 
     More particularly, the invention relates to a dynamometric tool as mentioned above, wherein the head and the first end of the sleeve are arranged and sized so that the head and the sleeve can assume a first relative orientation wherein the sleeve can slide freely with respect to the head so that the head is removable from the sleeve, and a second relative orientation wherein bearing members are arranged so as to maintain the sleeve in working position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics of this invention will become more evident by reading the description which follows with reference to the accompanying drawings, wherein: 
         FIG. 1  shows a detailed view of the arrangement of the sextant wrench end, once mounted and an additional cross-sectional view along the indicated axis. 
         FIGS. 2 ,  3 ,  4 , and  5  show various steps of the assembly of a tool according to the invention, with indexed views, a, in cross-section along longitudinal axis AA, and indexed views, b, in cross-section along the indicated axes. 
     
    
    
     EMBODIMENT(S) OF THE INVENTION 
       FIG. 1  presents a sextant wrench  1  according to the invention, ready to be used. The wrench defines a longitudinal axis AA and a transverse axis BB, shown in the drawings. 
     The wrench  1  has a sleeve  2  having a general shape of a stirrer bar. It has a lower surface  25  and an upper surface  29  parallel to axis AA. The sleeve also defines a first end formed with a concave wall  26  the general direction of which is substantially perpendicular to the upper surface  29 , completed at its base with a protrusion  21  extending the lower surface  25 . The protrusion  21  has a curved sidewall  211  and a substantially straight sidewall  212 . The right sidewall  212  is located in the extension of the lower surface  25  of the sleeve  2 . 
     The upper surface  29  of the sleeve  2  has a groove  22  defining a first edge  23  and a second edge  24 . The second edge  24  is located on the opposite side of the first end and has an indentation  26  at the end thereof, the role of which will become evident below. The upper surface  29  also has a bowl  27  designed for receiving a spring  6 , the utility of which will also be explained further down. The sleeve  2  further has an elongated cavity  28  positioned in its lower part and an axis parallel to the surface  25 . 
     The wrench  1  also comprises a head  3  comprising a semicircular part  31  extended by a part with a trapezoidal  32  shape. The inner head  3 , which is formed by a first housing  35  (see  FIG. 2 ), with a longitudinal axis AA, is located at the trapezoidal part  32  of the head  3  and outlets to the outside, thus forming an opening  33  (see  FIG. 3 ). The housing  35  has a lower wall  321 , finishing by a substantially perpendicular surface  311  ( FIG. 2 ) the role of which will be explained further down, and an upper wall  322 . The upper wall  322  is parallel to longitudinal axis AA. It has a lug  312 , typically located at two-thirds of the length thereof from the opening  33 . The lower wall  321  of cavity  35  is inclined with respect to longitudinal axis AA in such a way so that the two walls  321  and  322  diverge towards the interior of the cavity  35 . 
     The inner head  3  is also formed by a second housing  34 , cylindrical of axis BB, located at the end  31  of the head  3 . It is in connection with the first housing  35 . Preferably, the housing  34  is concentric with the area  31 . 
     The wrench  1  also has a tightening dowel  4 , equipped at its surface with grooves  41  separated among them by the parts  42 . It is inserted into the housing  34  of the head  3  and arranged along axis BB. When the dowel is positioned in the housing  34 , the grooves are oriented also along axis BB. As shown in cross-section AA of  FIG. 1 , the grooves  41  have not been machined over the entire height of the dowel  4 , but simply on a part not exiting on either of the two ends of the dowel  4 . The grooves  41  thus have a length lower than the total height of the tightening dowel  4 . The dowel  4  is placed so that one part of the grooves  41  is located opposite to the end of the housing  35 . 
     The first end of the sleeve  2  and the opening  33  are sized so that the head  3  is freely removable from the sleeve  2 , while defining a secure working position, wherein the head and sleeve are integral in translation. More particularly, it is planned to introduce the sleeve  2  in the head  3  by arranging these two elements according to a first relative orientation. Thus, the introduction is carried out by placing the lower surface  25  of the sleeve  2  in contact with the lower wall  321  of the housing  35 , in a parallel manner to the latter. The height of the end of sleeve  2  between the lower surface  25  thereof and the upper surface of the edge  23  is lower than the height defined by the opposing surfaces  321  and  322 , in a perpendicular manner to the surface  321 . Thus, when the sleeve is oriented by reference to the head, in a parallel manner to the surface  321 , it is possible to make it translate until the protrusion  21  abuts against the surface  311 . 
     The lug  312  and the groove  22  are positioned and sized so that when the protrusion  21  abuts against the surface  311 , the edge  23  has passed through the lug  312 . In addition, and advantageously, the lug  312  and the groove  22  are arranged so that when the protrusion  21  abuts against the surface  311 , the sleeve  2  can be rotated so that the lug  312  engages in the groove  22 . The indentation  26  of the edge  24  is particularly shaped in order to allow this rotation, without letting the edge  24  to come into contact against the wall  322  of the head  3 . The dimensional ratios between the lug and throat provide blocking of the sleeve  2  in translation along longitudinal axis AA, forwards and backwards. The surface  25  of the said sleeve  2  is in contact with the wall  321  only by a bearing surface  323  at the outlet end of the wall  321 . This support surface  323 , on the one hand, the lug  312  and the groove  22 , on the other hand, form bearing members that allow defining the working position of the sleeve, wherein the protrusion  21  is likely to engage with the grooves  41  of the dowel  4 . 
     Thus, given the structure of the grooves  41  described above, the tightening dowel  4  is blocked in translation along axis BB, while the sleeve  2  is in its working position. 
     It is understood that, for the disassembly of the sextant wrench  1 , it is the reverse operation, which is performed by tilting the sleeve  2  until the surface  25  is parallel to, and in contact with, the inner wall  321  of the cavity  35 . It will therefore be sufficient to translate the sleeve  2  along this wall to finish the extraction and completely separate the head and the sleeve. 
     The spring  6 , positioned in the bowl  27 , is designed to come into contact with the wall  322  of the housing  35 . This spring  6  takes action when the wrench  1  is rotated in the opposite direction of the tightening (anticlockwise) and exerts pressure on the sleeve  2  which allows the return of the protrusion  21 , present at the end of the sleeve  2 , in the following groove of the tightening dowel  4 , once the part  42  separating the two successive grooves is crossed. 
     The wrench  1  also has a flexible rod  5  of which one of the ends is inserted into the cavity  28  of sleeve  2 . The other end of the said flexible rod  5  is free and can evolve opposite to a graduated scale, thus indicating the applied torque. The user can therefore act on the rod  5  when it is desired to exert a controlled torque and will act directly on the sleeve  2  when it is desired to exert two maximum torques. 
     The rod  5  is secured to the sleeve  2  by means of a pin not shown in the drawing. The lug is arranged in order to maintain in position the flexible rod  5  by engaging with an annular groove contained by the rod  5 . This avoids any modification of the mechanical characteristics of the rod  5 , since the latter does not undergo either thermal or mechanical stress treatment. 
       FIGS. 2 ,  3 ,  4  and  5  show a method of assembling the sextant wrench  1 , with views  2   a ,  3   a ,  4   a  and  5   a  along longitudinal axis AA and cross-sectional views  2   b ,  3   b ,  4   b  and  5   b  along the indicated axes. More particularly, they show the method of assembly of the head  3  and the sleeve  2  of the sextant wrench  1  described above. In these figures, the dowel  4  is partially shown in dotted lines because it is normally placed after the step, corresponding in  FIG. 5 . 
     Firstly the sleeve  2  and head  3  are arranged in their first relative position. Then the first end of the sleeve  2  is inserted into the first housing  35  through the opening  33  and is translated within the housing  35  by retaining the first relative orientation of the sleeve  2  and of the head  3 . When the translation is completed, that is to say, when the first end  21  abuts against the surface  311 , the sleeve  2  and the head  3  are arranged in their second relative position, so that the sleeve  2  is placed in its working position. Advantageously, when the sleeve  2  is tilted so that the latter and the head  3  are placed in their second orientation, they are positioned directly to allow the bearing members to maintain the working position. More particularly, when the sleeve is placed in abutment against the surface  311  and then the sleeve and the head are placed in their second relative orientation, the lug  312  is inserted into the groove  22  through these operations. 
     Subsequently, extraction of the sleeve  2 , for maintenance or sterilisation, will be carried out by following the previous steps in the reverse direction. 
     Thus, a dynamometric tool is obtained, the head of which, is very simply and easily removable from the front, that is to say from the side of the first end of the sleeve, while ensuring maintaining perfectly the working position of the sleeve, with reference to the head and by securing the implementation of the dowel in the tool while it is being used. 
     Although the above description has been made with reference to a wrench sextant, it may be applied to other dynamometric tools. The above example is not exhaustive or limiting and the skilled person of the art may consider other embodiments within the reach of the latter, without however departing from the scope of this invention.