Abstract:
A pair of pliers which is automatically and continuously self-adjusting. In the approach phase, a mobile branch ( 2 ) is guided by a cradle with two intermediate ( 4 ) and rear ( 32 ) supports.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an adjustable pair of pliers that is operable with only one hand. 
     2. Description of the Related Art 
     EP-A-0 218 760 describes pliers of this type, in which the mutual guidance of the branches during the closure phase of the pliers is obtained by means of an articulated arm which passes through the space situated between the two handles. The closure phase is to be understood as meaning the step, in the use of the pliers, wherein, with the two jaws not in contact with an object that is to be grasped, forces are exerted on the handles in suitable directions that tend to bring the jaws closer together. 
     The main disadvantages of an articulated arm such as this are that there is a risk that the user will trap his fingers, that it is exposed to shock and dirt, and that any freedom of angular movement of the branches with respect to one another is eliminated. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide an adjustable pair of pliers that is operable one-handedly, of relatively simple design, and which affords improved comfort, flexibility and safety in use, while at the same time allowing excellent control over the closure phase. 
     To this end, the subject of the invention is an adjustable pair of pliers of the aforementioned type. 
     The adjustable pliers according to the invention may have one or more of the characteristics described in the dependent claims taken in isolation or in any technically feasible combination. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will now be described with reference to the appended drawings, in which: 
     FIG. 1 is a schematic view of an adjustable pair of pliers according to the invention, in the position of rest and during the closure phase; 
     FIG. 2 depicts, on a larger scale, a detail of FIG. 1; 
     FIG. 3 is a similar view of the pliers of FIG. 1, while an object is being clamped; 
     FIGS. 4 and 5 are similar views of two alternative forms of the pliers of FIGS. 1 to  3 ; and 
     FIG. 6 is a similar view of a second embodiment of the pliers according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The adjustable pliers  1  depicted in FIG. 1 consist of two branches  2  and  3 , of an articulation member or finger  4 , of a bearing element  5  and of an opening spring  6 . 
     The branch  2 , or moving branch, consists of a solid metal component which defines, from front to rear, that is to say from left to right when considering FIG. 1, a moving jaw  7 , an intermediate articulation region  8 , a rear bearing region  9  and a handle  10 . A sheath grip  11  may be attached to the latter, as depicted. 
     The jaws  7  have a toothed upper face  12  for gripping an object  13 . The face  12  comprises roughly flat and coplanar end regions  12 A, 12 B, separated by a region  12   c  in the form of a very open V. 
     The bearing region  9  comprises a convex lower surface  14  in the shape of a circular arc, the center O of which is a virtual point situated distinctly outside the contours of the tool, above the latter. The upper surface  15  of the branch  2 , in the same region, is straight, and approximates to the cord subtended by the circular arc  14 . 
     The handle  10  is curved, with its convex face facing upward. 
     The branch  3 , or fixed branch, defines, from front to rear, a fixed jaw  16 , attached to the main part of the branch by rivets, an intermediate articulation region  17 , a rear bearing region  18  and a handle  19  clad with a sheath  20 . 
     The jaw  16  comprises, on its lower face, a set of teeth  21  with two zones  21 A, 21 B, which are more or less planar and coplanar, flanking a zone  21 C in the form of a very open V. As depicted in the drawing, in the V zones of the jaws, only the rear part of the zone  12   c  and the front part of the zone  21 C are toothed. 
     The region  17  has an arched overall shape of center O. It is delimited by plain upper and lower surfaces  22  and  23  in the form of circular arcs of center O, and comprises an arched slot  24 . This is delimited by a plain upper surface  25  and by a sawtooth lower surface  26  forming a rack. Each of the surfaces  22  to  25  and the average line of the surface  26  are circular arcs of center O. The jaws  7  and  16  are entirely outside the circle of largest radius  22 . 
     The articulation member  4  (FIG. 2) is a component of elongate shape articulated freely more or less mid-way along its length by a pivot  27  on the region  8  of the branch  2 . This component comprises: 
     a concave upper surface  28  which is circular and has the same radius as the surface  25 ; 
     a lower surface which exhibits, at the rear, a set of sawtooth locking teeth  29  designed to engage with the set of teeth  26  and, at the front, a boss  30 . 
     In its bearing region  18 , the fixed branch  3  also comprises a blind housing  31  opened to the top and in which a slider  32  is accommodated. The latter is pushed upward by a spring  33  which in this instance is a helical compression spring, as far as a rest position as depicted, in which position the slider bears against a stop (not depicted) secured to the branch  3 . The slider  32  at its upper part comprises a bearing protrusion  34  for the bearing surface  14  of the branch  2 . 
     The opening spring  6 , which is far weaker than the spring  33 , is a tension coiled spring stretched between a point  35  on the branch  3  near the housing  31  and a point  36  on the branch  2  near the pivot  27  of the member  4  and situated between the circular arcs  22  and  26 . 
     In FIG. 1, the moving branch is depicted in fine line in its rest position and in bolder line during the closure. 
     At rest, under the effect of the spring  6 , the jaw  7  is pulled into its position of maximum separation from the jaw  16 . To reach this position, the surface  14  slides along the protrusion  34  of the slider  36 , until the member  4  comes into abutment against the rear end (the right-hand end in FIG. 1) of the slot  24 . Of course, as an alternative, other stop means could be provided for limiting the opening of the two jaws. 
     To grip an object  13 , a closure phase is first of all carried out by exerting a closing force F on the two handles as illustrated by the arrows. 
     Because of the relative stiffnesses of the two springs  6  and  33 , this force first of all causes the branch  2  to rock slightly about the protrusion  34 , until the upper surface  28  of the finger  4  presses against the upper surface  25  of the slot  24 . 
     Continuing this same force causes the surface  14  to slide to the left over the protrusion  34  and, at the same time, causes the surface  28  of the finger  4  to slide along the surface  25 , there being a small clearance between the finger and the set of teeth  26 . The two bearing points—intermediate  28  and rear  34 —form a cradle guiding the closing movement of the branch  2 . 
     Thus, throughout closing, the point  34  is fixed with respect to the branch  3 . In some instances, a sharp force exerted on the handles may cause slight compression of the spring  33 , but the latter immediately returns to its original length. The point  34  is therefore always fixed or practically fixed with respect to the branch  3 . 
     Throughout closing, the normals N 1  and N 2  to the points of contact  28 , 34  of the guide surface  25  and bearing surface  14  form a V, the point of which faces upward, that is to say away from the jaws. This V may have an angle slightly smaller than 90°, as depicted, or, as an alternative, an angle roughly equal to 90°. 
     This closing movement, which is performed against the action of the spring  6 , continues until the two jaws come into contact with the object  13 , then contact of the boss  30  with the set of teeth  26  causes the finger  4  to rock about its pivot  27  and brings the teeth  29  into contact with the set of teeth  26  (FIG.  3 ). 
     The point of contact of the moving jaws  7  with this object therefore defines a center of rotation, and continual application of the closing force on the two handles causes the branch  2  to rock about this center. 
     This movement, which is allowed by compression of the rear spring  33 , causes the teeth  29  to engage and become locked in the set of teeth  26 , this forming a new center of rotation for the branch  2 . Continuing to apply the force to the two handles tends to cause the branch  2  to rock about this new center, which gives the effect of clamping the object  13 . In this phase, the finger is braced between the set of teeth  26  and the surface  25 . When the force exerted on the two handles is released, the teeth  29  disengage from the bottom of the set of teeth  26  under the effect of the spring  33 . As the opposite end of the finger has remained in contact with the surface  25 , this upward movement causes the finger to rock about its pivot  27 . The finger thus quickly returns to its initial position of guidance on the surface  25 , and the spring  6  then returns the entire branch backward until the jaws are wide open. 
     The pliers thus described have a relatively simple design and are very smooth and precise during the closure phase. In addition, the concave overall shape of the intermediate region of the tool, which is obtained by virtue of the surfaces  23  and  15 , allows the front part of the pliers to be slipped into places which are difficult to access, for example behind a pipe. Likewise, the arched shape of the lower surface  22  gives the tool a particularly slender overall profile. 
     It should also be noted that by virtue of its arched shape, the slot  24  can easily comprise a rear part, the orientation of which approaches that of the moving handle  10 . This reduces the force that has to be exerted on the handles in order to start closing, by comparison with the customary scenarios in which the slot is straight as in the aforementioned EP-A-0 218 760. 
     Furthermore, nothing extends between the rear parts of the two branches, and this protects the user&#39;s fingers. 
     A projecting stud  37  is provided on the branch  2 , to the rear of the jaw  7 . Once the handles have been opened to a certain extent, this stud butts up against the surface  22 , thus limiting the opening of the handles. 
     The alternative form in FIG. 4 differs from thee previous one in the following respects: 
     the slot  24  is straight, as is the lower surface  22 . The surfaces  22 ,  25  and the average line of the surface  26  are mutually parallel; 
     the upper surface  23  is approximately straight, with an orientation diverging toward the rear with respect to that of the slot  24 ; the branch  3  has, facing this surface  23 , a lower surface  23 A roughly parallel to the former surface; 
     the bearing surface  14  is straight and roughly parallel to the upper surface  15 ; 
     this surface  14  bears, in rolling and/or in sliding, against a roller  38  borne by the upper end of the slider  32 ; and 
     the distal zone of the handle  19 , adjacent to the bearing region  18 , has a recess  39 . 
     Because of the recess  39 , the lower surface of the handle  19  closest to the jaws defines two bearing zones, proximal  40  and distal  41 , the respective average lines  42  and  43  of which form a certain angle between them. Thus, with respect to the average interior line  44  of the fixed jaw  16 , the line  42  makes an angle x 1  of between 45 and 55° and preferably of 50°, while the line  43  makes an angle x 2  markedly larger than x 1 , of the order of 75 to 90°. 
     The handle  10  furthest away from the jaws has a convex upper surface, and this defines a proximal zone  45  and a distal zone  46 , the respective average lines  47  and  48  of which form a certain angle between them. With respect to the average interior line  49  of the moving jaw  7 , the line  48  makes an angle y 1  of 45 to 55° and preferably of 50°, while the line  47  makes a larger angle y 2 , of the order of 75 to 90°. 
     The pair of surfaces  41  and  45  make the pliers&#39; closure phase described above easier by virtue of the orientation of the closing force F 1  exerted on them. The pair of surfaces  40  and  46  make the force of clamping the gripped object easier by virtue of the orientation of the force F 2  exerted on them. 
     The alternative form in FIG. 5 is similar to that in FIG. 4, except in the following two respects: 
     on the one hand, the slot  24  is arched, that is to say that its surface  25  and the average line of its surface  26  are circular arcs of center O; 
     on the other hand, the bearing surface  14  is also a circular arc, but its center O′ is distinct from the point O. 
     The embodiment in FIG. 6 operates in a similar way to the way described above, but with a structure modified as follows with respect to the embodiment in FIGS. 1 to  3 . 
     The slot  24  is omitted. The rack  26  is formed on the upper surface  23  of the intermediate region  17  of the fixed branch, and the jaw  7  exhibits, at the rear and at the bottom, a rearward facing nose  50 . The rack  26  is extended rearward by a plain bearing surface  114 . 
     The rack  32  is borne by the moving branch  2 , facing the surface  114 , and is urged downward by the spring  33  as far as a limit position predetermined by a stop, not depicted. 
     The points  35  and  36  of attachment of the opening spring  6  are located respectively at the rear end of the handle  19  and slightly to the rear of the slider  32 . 
     The finger  104  is articulated, by means of the pivot  27 , to the branch  2  so that the teeth  29  are a distance away from the nose  50  which is greater than the thickness of the part  17 , this being under the action of a spring  51  which keeps the front surface  30  of the finger in contact with the rear face of the intermediate part  17  of the fixed branch  3 . 
     At rest, the spring  6  keeps the two jaws in the wide open position, this position being determined by appropriate stops (not depicted) for the two branches. 
     When the two handles start to be brought together, the branch  2  pivots slightly in the clockwise direction about the point of contact between the slider  32  and the surface  114 , and this moves the pin  27  away from the rack  26  and brings the nose  50  into contact with the surface  22 . 
     Continued closing force applied to the two handles causes the slider  32  to move forward along the surface  114  and, at the same time, the nose  50  to move along the surface  22 , until the two jaws come into contact with the object  13  (FIG.  6 ). Here again we have the V with the point uppermost and with an acute angle formed by the normal N 1  and N 2 , as described above. 
     If the two handles continue to be closed, the branch  2  pivots first of all about its point of contact with the object  13 , compressing the spring  33 , until the teeth  29  of the finger  104  lock in the rack  26 . This engagement then defines a new center of rotation for the branch  2 , which allows the object  13  to be clamped as before. By virtue of the action of the spring  51 , the teeth  29  disengage from the rack  26  when the handles of the pliers are released.