Abstract:
Locking grips ( 1 ) designed so that their latch lock mechanism ( 8 ) cannot travel beyond a point of alignment of its three points but locks, slightly set back with respect to this alignment, by the snap-fastening of a relief ( 30 ) of a catch ( 28 ) borne by a lever ( 10 ) behind a tooth ( 19 ) of a front end of a link ( 13 ). The catch ( 28 ) forms a trigger ( 28 A) which allows the locking grips to be opened in a controlled way after the lever ( 10 ) has been released.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to locking grips of the type that allow a strong clamping force to be exerted for a long period of time, without intervention from the operator, on an object, or more frequently on two objects which need to be held together. 
     In order to give the tool a stable clamped position, a conventional latch lock or toggle mechanisms are designed to travel slightly beyond alignment at the end of clamping, relying for this on the elasticity of the parts. This leads to a serious drawback i.e. unclamping that of the locking grips leads to a sudden release of the elastic energy stored up during clamping, and this sudden release may cause an impact, which may be violent and dangerous, in the operator&#39;s hand. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to eliminate this drawback by providing locking grips of simple and ergonomic design that the operator can open while maintaining perfect control over this opening. In particular, if clamping has been achieved with just one hand, the operator will be able to open the locking grips with just one hand. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described with reference to the appended drawings, in which: 
     FIG. 1 is a view in longitudinal section of locking grips in accordance with the invention, in the wide-open position, and adjusted to clamp an object of minimum thickness; 
     FIG. 2 is a corresponding exterior view of the stationary handle; 
     FIG. 3 is a view similar to FIG. 1 showing the locking grips in the clamped position; 
     FIG. 4 is a view similar to FIG. 3 of an alternative form of the locking grips, in their position for clamping an object the thickness of which is close to a maximum value; 
     FIG. 5 is a view similar to FIG. 2 but corresponding to the adjustment of FIG. 4; 
     FIG. 6 is an exterior view of an alternative form equipped with an indicator that indicates the amount of clamping; 
     FIG. 6A is a partial view of an alternative form; 
     FIGS. 7 to  9  are partial views illustrating the use of the clamping indicator of FIG. 6; 
     FIG. 10 is a view similar to FIG. 3 relating to another embodiment of the locking grips according to the present invention; and 
     FIG. 11 is an exterior view of an alternative form of the locking grips of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The locking grips  1  depicted in FIGS. 1 to  3 , which are of a flat overall shape, consist of a stationary assembly  2  and a movable assembly  3 . 
     The stationary assembly  2  has the overall shape of a very elongate S which has a distal or front end part  4  constituting a stationary jaw, a proximal or rear end part  5  which is more or less parallel to the part  4  and constitutes a first handle or stationary handle, and an intermediate connecting part  5 A. In the normal position of use depicted, the jaw  4  is lower down than the handle  5 . 
     The movable assembly  3  comprises a movable or moving jaw  6  of triangular overall shape, and a toggle or latch lock mechanism S equipped with an adjusting device  9 . The lower rear vertex of the moving jaw  6  is articulated to the root of the stationary jaw by a pivot  7 . 
     The latch lock mechanism  8  comprises an operating lever  10 , the front end of which is articulated to the upper rear vertex of the moving jaw by a pivot  11 , and the rear end of which forms a second, movable or moving handle  12  situated beneath the stationary handle  5 . 
     The mechanism  8  also comprises a link  13 , the front end of which is articulated at an intermediate point along the lever  10  by a pivot  14 , and the rear end of which carries a pivot  15 . This pivot passes through elongate slots along the overall axis of the handle  5 , and these slots are provided in the two legs of a clevis piece  16 , which forms part of an adjusting device  9 . About mid-way along its length, the link  13  has a U-shaped protrusion  17  directed towards the handle  12 , which forms a slit  18  at its base. At its front end, this link has a single nesting tooth  19 , the front face of which forms an upper arc of a circle  19 A that is centered on pivot  14 , a lower arc of a circle  19 B of smaller radius, and a radial face  19 C, pointing downwards, connecting these two arcs. The face  19 C, which constitutes the nesting face, is more or less radially extending with respect to the pivot  14 . 
     The adjusting device  9  comprises a nut  20  fixed in the handle  5 , a screw  21  which passes through the nut, and an operating knob  22 . The front end of the screw passes, able to rotate freely, through the web of the clevis piece  16  and, within it, is equipped with a head against which the rear end of the link  13  can rest. The rear end of the screw  21  forms a square or a hexagon  23  slidably received within a matching recess in a sleeve  25 . The knob  22  is fixed to the sleeve in such a way that an internal flange  26  of the handle  5  is trapped between the knob and an external flange  27  of the sleeve  25 . Thus, the operating knob is mounted so that it can be rotated, but is incapable of translational movement, at the rear end of the handle  5 . 
     The mechanism  8  also comprises a locking/unlocking catch  28  articulated to the lever  12  by a pivot  29  close to the pivot  14 . On its inner side, pointing towards the handle  5 , the catch  28  has a recess delimited at the top by an upper triangular tooth  30  which forms a single nesting tooth, and at the bottom by a lower triangular stop tooth  31 . The upper edge  31 A of the latter is radial with respect to the pivot  29 . Furthermore, at its front end, close to the tooth  30 , the catch  28  has a protrusion  32 . In the example of FIGS. 1 to  3 , that part of the catch which bears the teeth  30  and  31  and the protrusion  32  consists of a separate attached component. For example, this component may be made of metal and the rest of the catch of plastic. 
     The mechanism  8  also comprises a multipurpose spring  33 . This spring comprises a helical rear part  34  hooked under tension onto the link  13  near to the pivot  15 , then a straight part  35  which extends, more or less along the overall axis of the stationary handle  5 , as far as the pivot  11 , then a hairpin-shaped part  36  which runs around the pivot  11  by one and a half turns. The hairpin shaped part  36  comes to bear on the protrusion  32  of the catch  28 , tending to make this catch rotate in the clockwise direction about the pivot  29 . 
     The way in which the locking grips, thus described, work is as follows. 
     To start off with, the locking grips are in their wide-open position depicted in FIG. 1, in which the face  19 C of the link is resting against the face  31 A and the tooth of the catch  30  is resting against the face  19 A of the link. This prevents the two handles from moving further apart from one another. This engagement is sustained thanks to the resting of the end  36  of the spring  33  and to the tension in its helical part  34 , which urges the moving jaw  6  open. The rear part  28 A of the catch  28  forms a trigger which protrudes slightly beneath an intermediate part of the lever  10 . 
     When the adjusting device  9  is in the state depicted, the screw  21  is screwed forward almost to its maximum extent. This is made visible, if there is no sheath covering this part, by the fact that the ends of the pivot  15  are guided in two longitudinal slots  37 (FIG. 2) in the handle  5  and lie almost at the front end of these slots. This setting corresponds to the clamping of an object  38  of minimum thickness, for example 1 mm thick, as depicted in FIG.  3 . 
     In order to grip the object  38 , the operator, using all four fingers, pulls up the handle  12  to bring it closer to the handle  5  (direction F in FIG.  1 ), which is wedged firmly in the palm of the operator&#39;s hand. The angle  11 - 14 - 15  gradually widens, and the moving jaw  6  moves closer to the stationary jaw  4 , tensioning the part  34  of the spring  33 , until the object  38  is gripped. At the same time, the tip of the tooth  19  moves closer to that of the tooth  30 , and contact between the tip of the tooth  30  and the arc  19 A, and between the tip of the tooth  31  and the arc  19 B being permanently sustained thanks to the part  36  of the spring. Throughout this movement, the catch  28  is immobilized with respect to the lever  10 , which means that the trigger  28 A also forms a purchase for the operator&#39;s index finger. 
     By continuing to move the two handles closer together, the operator increases the angle of the latch lock mechanism a little more and causes the tooth  30  to snap-fasten behind the tooth  19 , as depicted in FIG.  3 . The upper face of the tooth  30  is then more or less radial with respect to the pivot  14 , and the stresses due to clamping tend to widen the angle formed by the pin  29 , the tip of the tooth  30  and the pin  14 . The tip of the tooth  30  then butts against the surface  19 B of the link and prevents such widening. The tool has now reached its stable clamped position, for which the angle  11 - 14 - 15  is slightly less than 180°, and typically on the order of 170 to 175°. In this position, the trigger protrudes further beneath the lever  10 . The snap-fastening can thus be felt by the operator&#39;s index finger. 
     The front end of the link  13  then urges the part  35  of the spring  33  towards the handle  5  (upwards in FIG.  3 ), so that this part  35  presses the teeth  19  and  30  against one another with a force which is more or less at right angles to the straight line  11 - 15 . If the operator continues to bring the handle  12  up, the lever  10  will butt against the protrusion  17  of the link  8  before the points  11 ,  14  and  15  come into alignment. This guarantees that movement never goes beyond this point of alignment. Once the operator has released the handle  12 , the tool returns to its stable clamped position, because of the action of the spring  33 . 
     The device  9  can be set in two types of ways. For relatively gentle clamping, the snap-fastening  19 - 13  occurs before the slit  18  of the link is closed, which means that it is the latter&#39;s compressive longitudinal elasticity, predetermined by the geometry of its U-shaped protrusion, which defines the amount of clamping. This varies only little throughout the corresponding range of adjustment. 
     By contrast, for stronger clamping, corresponding to greater advancement of the screw  21 , the slit  18  closes up before snap-fastening  19 - 30  occurs, and this makes it possible for the object  38  to be clamped far more firmly. 
     To release the object  38 , the operator takes hold of the locking grips, brings their handles slightly closer together until 10 17 abutment is achieved. With the operator&#39;s index finger, he presses on the trigger  28 A and this disengages the tooth  30  from the tooth  19 , he then lets go of the handle  12  to allow the locking grips to open by themselves. This opening takes place under the action of the part  35  of the spring  33 , which pushes on the middle point  14  of the latch lock mechanism and its part  34 , which brings the ends closer together. The wide-open position is defined by the surface  19 C of the link and face  31 A of the catch coming into abutment with one another. 
     Thus, the elastic energy stored up upon clamping is released while the operator is gripping the locking grips tightly, and this prevents any explosive reaction in his hand. 
     In special conditions regarding the accessibility of the workpieces to be clamped, the operator may use the grips upside down with his palm on the branch  12 , two to four fingers on the branch  5 , and his thumb on the trigger  28 A. 
     FIG. 4 depicts an alternative form which differs from the previous one only in the following aspects: 
     the screw  21  is simply secured to the knob  22 , which means that the latter is a variable distance away from the rear end of the handle  5 , depending on the setting chosen; 
     the spring  33  has been split into three springs, each one fulfilling one of the functions described above: a spring  34 , wound around the pivot  7 , for moving the moving jaw away from the stationary jaw; a leaf spring  35  fixed in the handle  5  for urging the front end of the link away from this handle in the clamped position; and a hairpin-shaped spring  36  surrounding the pivot  11  for urging the front end of the catch  28  towards that of the link; 
     the catch  28  is made of one piece; and 
     the link  13  is rigid, that is to say that the slit  18  is omitted. 
     This alternative form works in the same way as the previous one, except that because of the rigidity of the link, there is no easy-to-obtain gentle clamping range unless, of course, flexibility is created in some other tensioned part of the grips. 
     FIG. 4 depicts the tool in its stable position for clamping an object  38  of maximum thickness (in practical terms, a few centimeters). In this case, the screw  21  is almost fully unscrewed, that is to say it is unscrewed far enough that the pivot  15  is brought close to the rear end of the slots  37 , as depicted in FIG.  5 . 
     FIG. 6 depicts an alternative form of the locking grips of FIG. 4, equipped with an indicator that indicates the amount of clamping. For that, the lever  10  has a protrusion  39  that projects towards the handle  5  and is pierced with a hole  40 . When the operator, effortlessly, brings the handle  12  closer to the handle  5  and grips the object  38  without exerting any appreciable clamping force, the protrusion  17  of the link becomes visible to a greater or lesser extent through the hole  40 , and this visibility can be changed by turning the knob  22  in one direction or the other. Accordingly, the emptier the hole  40 , the stronger the final clamping. 
     It will not be possible to see the indicator  40 - 17  unless the following two conditions are simultaneously satisfied: 
     1) jaws  4  and  6  are in contact with the workpiece; and 
     2) a very gentle force is applied to the handles  5  and  12 , i.e. just enough force to overcome the spring and keep the jaws in contact with the workpiece. 
     The indicator indicates, even though the workpiece has not yet been clamped, how much clamping force will be obtained after the clamping operation has been carried out to reach the stable position in which the teeth  19  and  30  are snap-fastened together. 
     The hole  40  may be provided in protrusions  39  situated on both sides of the protrusion  17 , so that the indicator will be clearly visible from both sides of the grips. These protrusions  39  then form the two perforated legs of a clevis piece receiving the protrusion  17 . 
     Thus, the indicator can be looked at by a left-handed or by a right-handed individual. It can also be looked at when the grips are being used in the upside-down position, with the operator&#39;s thumb on the trigger. 
     The example of FIGS. 6,  7 ,  8  and  9  shows a protrusion  17  of circular shape and a hole of circular shape. As an alternative, the indicator may consist of a protrusion  17  and a hole  40  of varying shapes. 
     Thus, another example is illustrated in FIG. 6A, with different shapes and a marking  40 A indicating the decreasing nature of the resulting tension, as has been explained with reference to FIGS. 7,  8  and  9 . 
     By way of example, FIGS. 7 to  9  illustrate three scenarios, but all the intermediate or extrapolated degrees of clamping can be obtained by turning the screw  22  to greater or lesser extent. 
     In FIG. 7, the hole  40  is almost clear, and final clamping will be firm; 
     In FIG. 8, the hole  40  is about half filled by the protrusion  17 , and final clamping will be moderate; and 
     In FIG. 9, the hole  40  is almost completely filled by the protrusion  17 , and final clamping will be light. 
     FIG. 10 depicts the application of the invention to locking grips the overall configuration of which is the opposite of the previous arrangement. In particular, the stationary jaw  4  is in line with the handle  5 , and the moving jaw  6  is on the same side of the straight line connecting the pivots  7  and  15  as the lever  10 . Furthermore, the screw  21  extends forwards, in the handle  5 , from the pivot  15  (possibly with the use of a clevis piece as before), and the nut  20  is a cylindrical knurled knob mounted so that it can rotate but is incapable of translational movement, more or less at a mid-way point along the stationary parts  2 . 
     The screw thread on the screw  21  and the nut  20  may be a single thread or a double thread, known per se. 
     The way in which this embodiment works and its properties are the same as what has been described earlier with reference to FIGS. 1 to  3 . 
     The invention can be extended to cover any type of locking grips, for example such as those disclosed in FR-A-2,237,730. 
     It should be noted that in each embodiment, the locking grips can be stored closed, simply by bringing the handles together, without it being necessary to operate the adjusting screw. The grips can therefore be closed for storage using just one hand, whereas for conventional grips two hands are needed, one to turn the adjusting screw and the other to close the grips. 
     What is more, the grips can be closed for storage more quickly, in a single action, because there is no need to turn the adjusting screw. 
     Locking grips in general, and the locking grips according to the invention in particular, can be made of cut, stamped, pressed then assembled sheet metal. Thus, the handles especially, are usually provided with sheaths made of synthetic resin (plastic) to make them comfortable and ergonomic during clamping. 
     Locking grips are often used for bringing together workpieces and holding them with a view to welding them. In such scenarios, there are showers of weld or welding slag which is still hot and the plastic sheath becomes encrusted with these; this soon causes the sheath to deteriorate, but more importantly may cause injury to the operator&#39;s hand in a subsequent operation. 
     The embodiment of FIG. 11, on the other hand, uses cast aluminium-alloy or aluminium sheaths: 
     which cannot become encrusted with showered weld material; 
     which do not deteriorate when they come into contact with hot workpieces; 
     and which despite everything, are still fairly light. 
     The upper sheath  41 , pushed over the handle  5  as far as where it joins the intermediate part  5 A, protects the mechanism (latch lock, spring, teeth  19  and  30 ) as far as the parts right next to the jaws, laterally and over the top of the tool. 
     The lower sheath  42 , pushed over the handle  12  may additionally have upwardly projecting reliefs which engage between the metal sheets of the handle  5  to fulfil functions such as: 
     clamping indicator (hole  40 ), on one leg  43 ; 
     stop  44 , interacting with the link as before, to prevent the latch lock mechanism from going beyond the point of alignment upon clamping. 
     As depicted, the sheath  42  may have a hole  45  so that the tool can be hung up.