Abstract:
A tool ( 1 ) comprising a head ( 4 ) having at least two engaging surfaces ( 10 ) for driving the screwing member by its at least partially matching shape and a device ( 5 ) for driving the head rotation. The head globally behaves as a single-piece part when the screwing member is driven in rotation. The head includes a zone ( 7 ) linking the engaging surfaces and parts ( 9 ) transmitting to the engaging surfaces a rotation force applied on the driving device. The linking zone is located between the force-transmitting parts and the engaging parts. The head is designed such that the action of the rotational driving device on the force-transmitting parts tends to deform the shape of the head so as to bring the engaging surfaces closer to each other when a rotational driving force is applied via the driving device on the screwing member. The present invention is, for example, applicable to flat open-end wrenches.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a driving tool for turning a screwthreaded member, particularly a hand tool, of the type comprising a head having at least two contact surfaces for driving the screwthreaded member by at least partial complementarity of form, and driving means for turning the head. The head behaves overall as a single piece when turning a screwthreaded member. The head includes a connecting region between the contact surfaces and the parts that transmit, to the contact surfaces, a turning force applied to the driving means. The connecting region is situated between the force transmitting parts and the contact surfaces. 
     The present invention applies, for example, to flat open-ended wrenches. 
     The head of such a wrench has two rigid open jaws, each of which has a contact surface for a screwthreaded member such as a nut. The two contact surfaces are opposite each other. 
     When a wrench of this kind is used to transmit a turning force to a nut, the jaws deform in such a way that the contact surfaces move apart. The nut therefore turns relative to the jaws. This modifies the pressure points between the nut and the jaws such that the force vectors (which are theoretically parallel) corresponding to the turning force move toward each other. This means that, for a given turning force, the magnitude of the corresponding forces increases. This increase leads in turn to an increase in the bending of the jaws. The phenomenon is self-amplifying and, above a certain value, there is total rotation of the nut in the jaws, often with destruction of the latter. The nut can then be said to have become in effect a cam, causing the wrench to burst. 
     The phenomenon therefore limits the turning forces that can be transmitted by any such flat open-ended wrench. This phenomenon is present in a general way in tools in which, unlike vices, for example, the clamping force of the contact surfaces is not independent of the turning force. 
     It is an object of the present invention to solve this problem by providing a tool of the aforementioned type capable for example of exerting increased turning forces on a screwthreaded member. 
     SUMMARY OF THE INVENTION 
     To this end, the subject of the present invention is a tool of the aforementioned type, characterized in that the head is designed so that the action of the driving means on the force transmitting parts tends to deform the geometry of the head such that the contact surfaces move toward each other when a driving force for turning a screwthreaded member is applied through the driving means. 
     In various particular embodiments, the tool can include one or more of the following characteristics, taken in isolation or in any of the technically possible combinations: 
     the head is designed so that the action of the driving means tends to deform the head elastically, 
     the driving means for turning the head comprise an actuating member for actuating the head, 
     the actuating member of the head is able to move relative to the latter in order to tend to move the contact surfaces toward each other, by lever action or by cam action on the force transmitting parts, when a driving force is applied to the actuating member to turn a screwthreaded member, 
     the head has a generally H configuration and comprises two arms connected by a central web, a distal region of each arm having one of the contact surfaces and the proximal regions of the arms forming said force transmitting parts, the two arms are able to move with respect to each other by deformation of the central web in order to move the contact surfaces toward each other by separation of proximal regions of the arms, and a distal region of the actuating member is positioned between the proximal regions of the arms in order to push them apart, by lever action or by cam action, when a driving force is applied to the actuating member to turn a screwthreaded member, 
     the actuating member is connected to the head by a flexible connection, 
     the flexible connection comprises a deformable part formed integrally with the head and the actuating member, 
     the actuating member and the head are separated or separable, 
     the tool comprises removable means connecting the head to the actuating member, 
     the actuating member can pivot with respect to the head, 
     the actuating member is part of a torque-measuring tool, 
     the tool comprises means for adjusting the tendency of the head to deform under the action of the driving means, 
     the head comprises two open jaws, each of which has at least one of the contact surfaces, and 
     the flexible connection is made of elastomer. 
     Here, the expression “head having at least two contact surfaces for turning a screwthreaded member by at least partial complementarity of form” denotes a head capable of driving such a member due to the fact that their respective shapes, which may be for example polygonal shapes, do not allow relative rotation. 
     In the present invention, the head also behaves functionally overall as a single piece of sufficient stiffness that, when in use, the functional geometry of the head remains essentially unchanged, except under the effect of deformation under load and the compensation of the latter according to the invention as will be described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A clearer understanding of the invention will be gained from reading the following description which is given purely by way of example and refers to the accompanying drawings, in which: 
     FIG. 1 is a schematic plan view of a flat open-ended wrench according to the present invention, ready to turn a nut; 
     FIG.  2  and FIG. 3 are views similar to FIG. 1, illustrating the wrench when a force is applied to its handle to tighten or loosen the nut, respectively; 
     FIG. 4 is an enlarged plan view of the head of the wrench of FIGS. 1 to  3 , illustrating schematically the action on the head of a relative rotation of the wrench handle; 
     FIG.  5  and FIG. 6 are enlarged top views showing the head and distal end of the handle in two variants of the wrench of FIGS. 1 to  4 ; 
     FIG. 7 is a schematic perspective view of a tool in another embodiment of the invention; and 
     FIG. 8 is a view similar to FIG. 1 illustrating yet another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a flat open-ended wrench  1  ready to turn a nut  2 . 
     The wrench  1  essentially comprises a head  4  and a separate handle  5 . 
     The head  4 , which can be made from a material with poorer properties than steel and in particular a modulus of elasticity of less than 150 gigapascals, has an H shape and comprises two straight arms  6  which are longitudinal with respect to a central axis X—X. The arms  6  are connected to each other by a central transverse web  7 . Each arm  6  has on either side of the web  7  a distal end region  8  (on the left in FIG.  1 ), and a proximal end region  9 . The web  7 , which is formed integrally with the arms  6 , is relatively thin and elastically deformable at least in flexion. 
     The distal end regions or jaws  8  each have a plane surface  10  for contact with the nut  2 . The contact surfaces  10  are turned toward the inside of the head  4  and are opposite each other. 
     As illustrated in exaggerated form in FIG. 4, the web  7 , being able to be deformed, forms a means of turning the arms  6  with respect to each other. 
     Thus, the arms  6  can be rotated with respect to each other in the plane of FIGS. 1 and 4, to each side of a rest position, as shown in solid lines in FIG.  1  and in dashes in FIG.  4 . 
     This rest position corresponds to no force being applied to the arms  6 . In this position the arms are parallel with each other and parallel with the axis X—X. 
     The distal and proximal end regions  8 ,  9  can therefore be moved toward and away from each other respectively by the flexural deformation of the web  7 . 
     In particular, the arms  6  can be moved between their rest position and a position in which their distal end regions  8  are closer together (FIG. 4) while their proximal end regions  9  are further apart. 
     When a screwthreaded member  2  is inserted between the distal end regions  8  of the arms  6  of the head  4 , the mobility of the arms  6  is thereby limited. 
     The handle  5  is an elongate bar of axis Y—Y and has a slightly shorter transverse dimension than the gap between the two proximal end regions  9  of the arms  6 . 
     The distal end region  12  of the handle  5  fits with a slight looseness between the proximal end regions  9  of the arms  6 . 
     In the rest position shown in FIG. 1, the longitudinal axis X—X of the head  4  coincides with the longitudinal axis Y—Y of the handle  5 . 
     The nut  2  is a hexagonal nut that fits between the distal end regions  8  of the arms  6 . The contact surfaces  10  of the head  6  are alongside two opposite sides of the nut  2 . The contact surfaces  10  of the head  4  make the latter partially complementary in shape to the nut  2 . 
     The handle  5  can be rotated with respect to the head  4  in the plane of FIG. 1, to each side of its rest position, between two positions of separation of the arms  6 , one shown in FIG.  2  and the other in FIG.  3 . 
     In FIG. 2, the handle  5  has pivoted with respect to the head  6  in the direction  14  in which the nut  2  is tightened. The distal end region  12  of the handle  5  is now pressing on a point  15  on the free end of the lower arm  6  (as viewed in FIG. 2) of the head  4 , and on a point  16  close to the web  7  on the other arm  6 . Points  15  and  16  are separated from each other longitudinally along the axis X—X. The axes X—X and Y—Y are therefore also inclined with respect to each other. 
     In the other position of separation, illustrated in FIG. 3, the handle  5  has pivoted with respect to the head  4  in the direction  18  in which the nut  2  is loosened. The distal end region  12  of the handle  5  is now pressing on a first point  15  on the upper arm  6  (as viewed in FIG. 3) of the head  4  and on a second point  16  on the other arm  6  of the head  4 . The pressure points  15  and  16  therefore have a relative longitudinal position analogous to that of points  15  and  16  in FIG.  2 . The axes X—X and Y—Y are therefore also inclined with respect to each other. 
     Operation of the wrench  1  is as follows. 
     When the nut  2  is to be tightened, a force  20  is applied, as illustrated in FIG. 2, to the proximal end region  21  of the handle  5 , tending to pivot the latter in direction of rotation  14 . 
     The handle  5  thus arrives at the position shown in FIG.  2  and turns the head  4  in direction  14 . A tightening torque is therefore applied to the nut  2  because of the partial complementary form between the head  4  and the nut  2 . The proximal end regions  9  thus form parts that transmit the force from the handle  5  to the contact surfaces  10  and therefore to the nut  2 . 
     Simultaneously, the handle  5  is acting, via the two longitudinally offset pressure points  15  and  16 , as a first-order lever and tends to drive apart the proximal end regions  9  of the arms  6  of the head  4 . 
     In this way the distal end regions  8  of these arms  6  tend to move toward each other. This effect therefore tends to compensate for the tendency of the distal end regions  8  of the arms  6  to move apart and so limit the relative rotation of the nut  2  with respect to the head  4 . 
     Conversely, relaxation of the force  20  on the handle  5  allows the distal end regions  8  of the arms  6  to return to the rest position. 
     In the same way, when a force  24  is applied to the proximal end  21  of the handle  5  to loosen the nut  2 , the handle  5  moves to the position shown in FIG.  3  and tends on the one hand to drive the nut  2  in direction of rotation  18 , and on the other hand to push together the distal end regions  8  of the arms  6  by lever action. 
     The lever action produced by the handle  5  thus tends to oppose the separation of the contact surfaces  10  by the nut  2 . 
     As before, relaxing the force  24  on the handle  5  allows the distal end regions  8  of the arms  6  to return to the rest position. 
     It will thus be observed that, in both driving directions, the wrench  1  limits rotation between the nut  2  and the head  4  and also limits the risk of the head  4  breaking. 
     Consequently the wrench  1  is capable of transmitting larger turning forces than a conventional flat open-ended wrench, and yet the wrench  1  can access a screwthreaded member as easily as a conventional open-ended wrench. 
     By varying the dimensions and shape of the head  4 , it is possible either only to compensate for or to limit the tendency of the contact surfaces  10  to separate, but also to overcome this tendency by a relatively large effect of closing-up of these contact surfaces  10  under the action of the handle  5 . Consequently, for certain geometries of the wrench  1 , within certain ranges of turning forces transmitted to a nut  2 , an effect of increased clamping by the contact surfaces  10  on the nut  2  is observed when a force is applied to the handle  5 . 
     The wrench  1  in FIG. 5 differs from that in FIGS. 1 to  4  in that the head  4  and the handle  5  are not separated but are connected by a longitudinal blade  26  formed integrally with the web  7  of the head  4  and the distal end region  12  of the handle  5 . 
     This blade  26  can deform, for example in flexion, such that it forms, between the head  4  and the handle  5 , a flexible link allowing the latter to pivot with respect to the head  4  into the positions shown in FIGS. 2 and 3. 
     The proximal end regions  9  of the head  4  include four internal beads  27  arranged in pairs on these regions  9 . The beads  27  of a given region  9  are spaced out and are located opposite the beads  27  of the other region  9 . These beads  27  form reliefs where the handle  5  presses on the proximal end regions  9  when the handle  5  is moving, with respect to the head  4 , to the positions shown in FIGS. 2 and 3. It will be seen that in the rest position shown in FIG. 5, the four beads  27  are practically in contact with the handle  5 . 
     In a variant, which is not illustrated, the blade  26  need not be formed integrally with both the head  4  and the handle  5 , but welded to the head  4  and/or to the handle  5 . 
     In a variant, which is not illustrated, the blade  26  is replaced by an additional elastomeric part, attached to both the head  4  and the handle  5  by means known per se (mechanical means or injection overmolding, for example). 
     In the variant shown in FIG. 6 the head  4  comprises reliefs where the handle  5  presses against the proximal end regions  9  of the arms  6 , namely a pair of beads  28  and a pair of pins  29 . These reliefs project from the arms  6  toward the distal end region  12  of the handle  5 . 
     Both the beads  28  and the pins  29  are opposite each other. However, in other variants the beads  28  and the pins  29  may be arranged differently. 
     The beads  28  are each formed integrally with the proximal end region  9  of an arm  6  and are further from the central web  7  than the pins  29 . 
     The pins  29 , which are cylindrical, are each housed in a recess  30  formed in the proximal end region  9  of an arm  6 . 
     The head  4  has two pairs of recesses  30  that can house the pins  29  and are spaced apart along the axis X—X. 
     The spacing along the axis X—X between the pins  29  and the beads  28  can thus be modified. 
     The beads  28  and the pins  29  define the pressure points of the handle  5  on the head  4  so that it fulfills its lever function. By modifying the position of the pins  29 , the magnitude of the tendency of the surfaces  10  to come together when a turning force is applied to a nut  2  through the handle  5  can thus be adjusted. 
     Thus, the smaller the spacing between the bead  28  and the pin  29  on which the handle  5  is pressing, the greater this tendency will be. 
     FIG. 7 illustrates another tool  1  according to the invention which differs from the wrench of FIGS. 1 to  4  in that the handle has been replaced by a T-shaped actuating member  5 , which thus comprises a torque-transmitting bar  32  extended by a hand grip  33 . 
     The distal end region  34  of the actuating member  5  fits slightly loosely between the proximal end regions  9  of the arms  6 . As in FIG. 5, the proximal end regions of the head  4  have four beads  27  where the region  34  of the actuating member  5  presses on the head  4 . 
     This region  34  is rectangular in section and contains a transverse bore  36 . 
     A transverse hinge pin  37  passes through both arms  6  and through the bore  36 . 
     This hinge pin  37  connects the actuating member  5  to the head  4 , allowing the actuating member  5  to pivot with respect to the head  4  about the axis of the hinge pin  37 . 
     The bar  32  can thus be positioned out of the plane of the head  4 , e.g. obliquely or at right angles to this plane as shown in FIG.  7 . 
     This ability to pivot makes it possible to adapt to varied conditions of use, e.g. for tightening nuts that are difficult to access. 
     The user then adapts the force that he is applying in order to always obtain a turning force on the screwthreaded member. 
     In addition, the play between the bore  36  and the hinge pin  37  is sufficiently great so that when, in the position shown in FIG. 7, a turning force is applied through the hand grip  33  to a nut, the bar  32  can be rotated about its longitudinal axis with respect to the head  4 . The region  34  of the bar  32  then presses on the beads  27  and thus tends to push the regions  9  of the arms  6  apart by a cam action and so tends to close up the contact surfaces  10  as before. 
     In a variant, the hinge pin  37  can be removed to allow the head  4  and the member  5  to be separated. This allows heads  4  of different sizes and shapes to be connected to the actuating member  5 . 
     In another embodiment shown in FIG. 8, the handle  5  of the wrench seen in FIGS. 1 to  4  has been replaced by the output end  40  of a torque wrench  41 . 
     Although the above description is appropriate to a flat open-ended wrench, the invention can be applied to other types of tools.