Abstract:
The snap hook of the invention comprises a snap hook body closed by two closure fingers pivoting in opposite directions. The two closure fingers are separated by an insertion space. The insertion space has a width sufficient to allow the insertion of a loop oriented perpendicularly to the mean direction of the closure fingers. The insertion space becomes progressively narrower in the direction of the second end of the closure fingers. As a result, a loop may be inserted between the closure fingers, around the second end of the snap hook body, and pushing the loop, automatically inserts it into the snap hook, which thereafter remains locked.

Description:
TECHNICAL FIELD OF THE INVENTION  
       [0001]     The present invention concerns safety snap hooks requiring two separate actions to open them.  
         [0002]     The snap hooks usually employed in mountaineering, potholing, and when working overhead in the construction and other industries generally comprise an open ring snap hook body having facing first and second ends separated by an opening, with a closure finger having two ends, articulated by its first end to the first end of the body to pivot toward the interior of the snap hook between a closed position in which its second finger end is in contact with the second end of the body and an open position in which its second finger end is offset from the second end of the body, return spring means spring-loading the closure finger toward the closed position.  
         [0003]     Clearly, in the absence of additional safety means, the closure finger may accidentally pivot toward the open position when loaded, for example by a force applied by a tie such as a rope that enters the snap hook.  
         [0004]     Safety snap hooks having additional locking means to prevent accidental pivoting toward the open position have long been envisaged.  
         [0005]     For example, the locking means may comprise a threaded ring straddling the second end of the finger and the second end of the body in the closed position, or a spring ring that is pushed back into the straddling position, or a lever bearing against the closure finger to prevent it pivoting. All these means lock the closure finger against rotation.  
         [0006]     The problem is that the locking action necessitates intentional action by the user, for example rotation of the locking ring. As a result, locking is not certain, as the user may forget to carry out the action necessary to obtain locking. As a result, safety requirements are not always complied with.  
         [0007]     The document FR 2 766 884 describes a safety snap hook in which safety is automatically assured by providing two closure fingers that pivot in two opposite directions. Thus, a force exerted in one of these directions could open one of the two fingers, but necessarily holds the second finger in the closed position, with the result that the snap hook remains closed.  
         [0008]     In the above document, the snap hook comprises an open ring snap hook body having facing first and second ends separated by an opening. An exterior closure finger is articulated by passing its first end through the first end of the snap hook body to pivot in a first direction toward the exterior of the snap hook. An interior closure finger is articulated by its second end to the first end of the snap hook body and is able to pivot in a second direction toward the interior of the snap hook. In several embodiments, the closure fingers consist of an elastically flexible material wire that is bent to form an elongate loop whose curved ends are engaged in respective offset transverse holes in the snap hook body.  
         [0009]     In the closed position, the two closure fingers have their second ends in contact with the second end of the snap hook body, and the two closure fingers are parallel to each other and close together, the overall transverse dimension of the closure fingers being substantially equal to the transverse dimension of the metal wire forming the snap hook body.  
         [0010]     Safety is correctly assured with this kind of prior art snap hook structure with two closure fingers. However, inserting a tie such as a rope into the snap hook necessitates a two-fold maneuver: a first maneuver consists in moving the exterior closure finger toward the exterior of the snap hook, followed by engaging the tie such as the rope between the two closure fingers; a second maneuver consists in pushing the interior closure finger toward the interior of the snap hook and moving the tie such as the rope toward the interior space of the snap hook. The two closure fingers are then returned to the closure position by the return spring means. An opposite two-fold operation is necessary to remove the tie such as the rope from the snap hook.  
         [0011]     These operations, in particular for inserting a tie such as a rope into the interior of the snap hook, are relatively complex, and generally necessitate the use of both the user&#39;s hands, one to hold the snap hook or the exterior finger to be opened, and the other to hold the tie such as the rope to be inserted. As a result, it is not possible to operate this kind of safety snap hook with only one hand, in contrast to basic snap hooks with no safety feature, into which a rope may be inserted by simply pressing the rope radially toward the interior of the snap hook against the closure finger.  
         [0012]     The document U.S. Pat. No. 5,480,202 A discloses a crane hook for lifting loads of several tonnes, comprising a J-shaped hook body with an upper first end having an attachment hole, and whose curved lower portion may be closed by an interior closure plate and an external closure plate.  
         [0013]     Both the closure plates are articulated at their first end to an intermediate region of the hook body, at a significant distance from the first upper end with the attachment hole.  
         [0014]     In the closed position, the exterior closure plate has an intermediate region bearing on the second end of the hook body. The two plates diverge progressively in the direction of their free second end. The object of these means is to prevent untimely snagging of the crane hook on fences, electrical cables or other construction elements. Apart from the fact that the device does not relate to closed-ring safety snap hooks, the document does not mention the problem of using a snap hook with only one hand, and the means described do not provide for such use. Moreover, the second end of the exterior plate, which projects significantly away from the second end of the hook body, constitutes a bulky member that would not provide satisfactory safety if applied to a snap hook: a rope inserted into the hook but able to slide along it could abut against the second end of the exterior plate and enter the interior of the hook a second time and thereby escape from the interior of the latter of its own accord.  
       SUMMARY OF THE INVENTION  
       [0015]     The problem addressed by the present invention is that of designing a new safety snap hook structure, that assures as good automatic safety as a prior art snap hook with two opposed closure fingers, and that simultaneously allows easier maneuvering to insert a tie such as a rope into the snap hook, enabling the tie such as the rope to be inserted with only one hand.  
         [0016]     To achieve the above and other objects, the invention proposes a safety snap hook for attaching a tie, comprising: 
        an open ring snap hook body having a first end and a second end facing each other and separated by an opening,     an exterior closure finger with two ends, articulated at its first end to the first end of the snap hook body to pivot relative to the snap hook body in a first direction toward the exterior of the snap hook, between a closed position in which its second end is in contact with an exterior surface of the snap hook body and an open position in which its second end is offset from the second end of the snap hook body, and with return spring means for spring-loading the exterior closure finger toward its closed position, and     an interior closure finger with two ends, articulated at its first end to a point at or near the first end of the snap hook body to pivot relative to the snap hook body in a second direction toward the interior of the snap hook, between a closed position in which its second end comes into contact with an interior surface region of the snap hook body, and an open position in which its second end is offset from the second end of the snap hook body, with return spring means for spring-loading the interior closure finger toward the closed position,     an insertion space is formed between the two closure fingers,     the insertion space has a width sufficient to allow the insertion of the tie formed into a loop oriented perpendicularly to the mean direction of the closure fingers,     the insertion space becomes progressively narrower in the direction of the second end of the closure fingers, and     the interior surface region and the exterior surface region are set back from the second end of the snap hook body, said second end of the snap hook body forming an insertion nose that projects into the insertion space.        
 
         [0024]     Increasing the width of the insertion space necessarily increases the overall bulk of the snap hook. Now, this overall bulk must often be maintained within relatively small values, as is the case for mountaineering and potholing, and/or for attachments that are easily movable. It is therefore preferable to choose an insertion space width that is just sufficient to allow the insertion of the above kind of loop formed by curving a tie of the kind routinely used, advantageously a rope of the usual diameter.  
         [0025]     In practice, when the snap hook is to be used for attaching running lines such as mountaineering or potholing ropes, the loop has a diameter from approximately 2.5 cm to approximately 4 cm, frequently approximately 3 cm. For this reason it is advantageous for the width of the insertion space to be not very different from the diameter of the loop.  
         [0026]     Greater dimensions are nevertheless possible and advantageous for snap hooks used in industry, for example, or for fixed attachments that it is not required to move frequently and where easier maneuvering is a requirement.  
         [0027]     The insertion nose advantageously has an end section that is offset from both the closure fingers, forming two gaps between the insertion nose and the exterior closure finger and the interior closure finger, respectively.  
         [0028]     In one practical embodiment, the interior closure finger is formed of an elastically flexible material wire bent to form an elongate loop whose curved ends are engaged in two respective transverse holes offset from the first end of the snap hook body to constitute the articulated first end of the interior closure finger, the elasticity of the wire forming the interior closure finger returning it to the closed position.  
         [0029]     One option is for the exterior closure finger to be a generally cylindrical rod articulated to the first end of the snap hook body.  
         [0030]     In this case, it is advantageous if the first end of the exterior closure finger comprises an interior arm inside the interior space of the snap hook and to which the interior closure finger is articulated, said interior closure finger being formed of an elastically flexible material wire bent to form a loop whose curved ends are engaged in respective offset transverse holes in the interior arm to constitute the first articulated end of the interior closure finger, the inherent elasticity of the wire forming the interior closure finger then returning the two closure fingers to the closed position.  
         [0031]     Another option is for the exterior closure finger to be formed of an elastically flexible material wire bent to form an elongate loop whose curved ends are engaged in two respective offset transverse holes in the first end of the snap hook body to constitute the articulated first end of the exterior closure finger, the inherent elasticity of the wire forming the exterior closure finger returning it to the closed position. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]     Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments, given with reference to the appended drawings, in which:  
         [0033]      FIG. 1  is a side view of a first embodiment of a snap hook according to the present invention, shown closed;  
         [0034]      FIG. 2  is a side view of a second embodiment of a snap hook according to the present invention, shown closed;  
         [0035]      FIG. 3  is a perspective view of the  FIG. 2  snap hook, shown closed;  
         [0036]      FIG. 4  is a perspective view of the  FIG. 3  snap hook during insertion of a loop into the insertion space; and  
         [0037]      FIG. 5  is a perspective view of the  FIG. 3  snap hook during penetration of the loop into the snap hook. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     Both embodiments of a safety snap hook according to the invention shown in the figures comprise an open ring snap hook body  1  having facing first and second ends  2 ,  3  separated by an opening  4 .  
         [0039]     An exterior closure finger  5  has a first end  6  and a second end  7 . The exterior closure finger  5  is articulated by its first end  6  to the first end  2  of the snap hook body  1  to pivot in a first direction toward the exterior of the snap hook, as shown by the arrow  8 , between a closed position shown in  FIG. 1  or  FIG. 2  in which its second end  7  is in contact with an exterior surface region  3   a  of the snap hook body  1  in the vicinity of its second end  3 , and an open position in which its second end  7  is offset from the second end  3  of the snap hook body  1 .  
         [0040]     Return spring means, to be described later, spring-load the exterior closure finger  5  toward the closed position.  
         [0041]     An interior closure finger  9  has two ends  10  and  11 . The interior closure finger  9  is articulated at its first end  10  to the snap hook body  1  to pivot in a second direction  12  toward the interior of the snap hook between a closed position shown in  FIGS. 1 and 2  in which its second end  11  is in contact with an interior surface region  3   b  of the snap hook body  1  and an open position in which its second end  11  is offset from the second end  3  of the snap hook body  1 .  
         [0042]     Return spring means spring-load the interior closure finger  9  toward its closed position.  
         [0043]     In both the embodiments shown in  FIGS. 1 and 2 , and as seen better in  FIG. 3 , the interior closure finger  9  has a structure known in the art comprising an elastically flexible wire conformed into an elongate loop, the two ends  91  and  92  of the wire constituting the first end  10  of the interior closure finger  9  and for this reason being oppositely curved at 90° in order to be engaged in two offset transverse holes forming the articulation of the interior closure finger  9 . The wire may advantageously be steel wire with a diameter from approximately 1 mm to approximately 2 mm.  
         [0044]     The elastic wire is formed so that its inherent elasticity tends to return the interior closure finger  9  toward the closed position, so that no other return spring means are needed.  
         [0045]     In the first embodiment, shown in  FIG. 1 , the two curved ends  91  and  92  of the wire enter two transverse holes provided in the first end  2  of the snap hook body  1 .  
         [0046]     In the second embodiment, shown in  FIG. 2 , the two curved ends  91  and  92  of the wire are engaged in two transverse holes provided in a short interior arm  50  of the exterior closure finger  5 , and are therefore in the vicinity of the first end  2  of the snap hook body.  
         [0047]     In the embodiment shown in  FIG. 1 , the exterior closure finger  5  is also formed by an elastically flexible material wire bent to form an elongate loop whose curved ends  51  and  52  are engaged in two respective offset transverse holes in the first end  2  of the snap hook body  1  to constitute the articulated first end  6  of the exterior closure finger  5 . The inherent elasticity of the wire also returns the exterior closure finger  5  to the closed position.  
         [0048]     In the second embodiment, shown in  FIG. 2 , the exterior closure finger  5  has a conventional generally cylindrical and slightly curved rod structure, and return spring means must be provided to return it to the closed position. One option is to provide conventional return spring means, in the form of a compression spring engaged in an axial housing of the closure finger to bear on a tongue fastened to the snap hook body  1 . A second option is to exploit the spring return force of the interior closure finger  9 , using the arrangement shown in  FIG. 2 : in this case, the first end  6  of the exterior closure finger  5  comprises an interior arm  50  inside the interior space of the snap hook and to which the interior closure finger  9  is articulated. The inherent elasticity of the wire constituting the interior closure finger  9  then returns the two closure fingers  5  and  9  to the closed position.  
         [0049]     In all the embodiments shown in the figures, the snap hook further comprises an insertion space  13 , between the two closure fingers  9  and  5 , and of sufficient width L to allow the insertion of a loop  16  (see  FIGS. 4 and 5 ), as described later. In practice, the greatest width L of the insertion space  13  may be from approximately 2.5 cm to approximately 4 cm in snap hooks of the kind usually employed for mountaineering and potholing, this width L being adapted for the insertion of a loop  16  of rope of the usual diameter. The width L may advantageously be approximately 3 cm.  
         [0050]     The insertion space  13  becomes progressively narrower in the direction of the second end  11  or  7  of the closure fingers  5  or  9 , as may be seen in  FIGS. 1 and 2 . In practice, the exterior closure finger  5  is slightly convex toward the exterior, giving the snap hook an exterior contour similar to the contours of the prior art snap hooks usually employed. Conversely, the interior closure finger  9  is strongly convex toward the interior of the snap hook. To allow sufficient opening movement, as indicated by the arrow  12 , the two lateral branches  9   a  and  9   b  of the elastic wire are separated from each other, as shown in  FIG. 3 , by a distance slightly greater than the diameter of the wire forming the snap hook body  1 , so that, in the open position, the two lateral branches  9   a  and  9   b  of the wire can pivot on either side of the central branch of the snap hook body  1 .  
         [0051]     Advantageously, as shown in  FIGS. 1 and 2 , the interior surface region  3   b  and the exterior surface region  3   a  on which the respective second ends  11  and  7  of the closure fingers  9  and  5  bear in the closed position, are set back from the second end  3  of the snap hook body  1 . As a result, the second end  3  of the snap hook body  1  forms an insertion nose  14  that projects into the insertion space  13 .  
         [0052]     The insertion nose  14  may advantageously have an end section that is offset from both the closure fingers  5  and  9 , forming two gaps  20  and  21  between the insertion nose  14  and the exterior closure finger  5  and the interior closure finger  9 , respectively. The end section of the insertion nose  14  may also have a width L1, in the general plane of the snap hook, that becomes narrower toward the end of the insertion nose  14  or the second end  3  of the snap hook body  1 .  
         [0053]     The end section of the insertion nose  14  may advantageously have a length L2 (see  FIG. 2 ) greater than or equal to the radius of the tie  100  forming the loop (see  FIGS. 4 and 5 ).  
         [0054]     The manner in which a safety snap hook according to the invention may be used is described next with reference to  FIGS. 4 and 5 .  
         [0055]     In  FIG. 4 , the snap hook is closed, as in  FIG. 3 . The insertion space  13  is sufficiently wide to allow the user to insert a loop  16  formed of the tie  100  that is to be inserted into the snap hook. For example, the loop  16  is formed in a rope  100  whose diameter D is appropriate to the intended use. For example, the diameter D is of the order of 6 to 11 mm. As a result, the loop  16  has a diameter D1 from approximately 2.5 cm to approximately 4 cm, as a function of the diameter of the rope. The width L of the insertion space  13  is chosen to be only slightly different from the diameter D1 of the loop  16  in the tie such as the rope  100  to be used.  
         [0056]     The user is therefore able to insert the loop  16  into the insertion space  13 , holding the loop  16  in a plane substantially perpendicular to the mean direction I-I of the closure fingers  5  and  9 .  
         [0057]     Then, as shown in  FIG. 5 , the user is able to push the loop  16  by applying a longitudinal force F in the mean direction I-I of the closure fingers  5  and  9 , while holding the loop  16  in a plane perpendicular to the direction I-I. As a result, the loop  16  is engaged in the progressively narrower space, and, if the snap hook comprises an insertion nose  14 , the loop  16  is engaged around the insertion nose  14  in the gaps  20  and  21  (see  FIGS. 1 and 4 ). As it moves in the direction of the force F, the loop  16  simultaneously pushes the two closures fingers  5  and  9  back toward their open positions, with the result that one strand  16   a  of the loop  16  is inserted into the interior space of the snap hook, while the other strand  16   b  of the loop  16  lies outside the snap hook. Finally, the tie  100  such as the rope passes through the interior space of the snap hook, which is what was intended. In this position, the tie  100  may no longer escape from the snap hook, regardless of the force exerted in the closure fingers  5  and  9 , one of the fingers being always abutted in the closure position regardless of the direction of the force.  
         [0058]     The penetration movement of the loop  16  into the snap hook, shown in  FIGS. 4 and 5 , may be executed with only one hand, which considerably facilitates using the snap hook.  
         [0059]     Clearly the insertion nose  14  with its end section offset from both of the closure fingers  5  and  9  facilitates positioning the loop  16  on either side of the second end  3  of the snap hook body  1 . Nevertheless, a snap hook in accordance with the invention may be designed that operates relatively satisfactorily even with no space between the end section of the insertion nose  14  and one or the other of the closure fingers  5  and  9 .  
         [0060]     The present invention is not limited to the embodiments that have just been described explicitly, but encompasses variants and generalizations thereof within the scope of the following claims.