Abstract:
A swivel attachment device comprising a pair of rings able to rotate freely with respect to one another around an axis of rotation defined by a central pivot-pin. At least one of the rings is in the form of a hook delineating a lateral access space. A removable closing part, composed of a spacer through which a fixing screw passes, is able to close said space performing partial take-up of the tensile forces.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a swivel attachment device comprising a pair of rings able to rotate freely with respect to one another around an axis of rotation defined by a central pivot-pin, at least one of the rings being in the form of a hook delineating a space for lateral access. 
     STATE OF THE ART 
     A known swivel of the kind mentioned comprises two rings able to rotate around a central pivot-pin, wherein each ring is formed by end-to-end assembly of the ends of two U-shaped parts. Two screws are necessary to close each ring. In the assembled position of the ring, the two screws are sunk in the body of the ring, and are not visible from the outside. In the case of incomplete closure with a single screw, or of insufficient tightening, the visible state of the ring appears normal, but to the detriment of its mechanical strength. 
     Other known attachment products concern shackles able to rotate around a closed ring. These devices have large dimensions and are not very practical to use. If the shackle is not well suited to the load, the tractive force can be applied on the edge of the shackle and is therefore not centred on the axis of rotation of the swivel assembly. 
     Instead of shackles, snap-hooks also exist coupled with rotation to a ring by a pivot-pin. Snap-hooks have pivoting fingers with automatic closing able to be latched. The large dimensions of the latter do not make handling operations easy, and the load take-up by the closed finger is insufficient. Such a swivel system is described in the document U.S. Pat. No. 5,634,246. 
     OBJECT OF THE INVENTION 
     The object of the invention consists in providing an openable swivel of smaller dimensions, and having a closing system that is resistant and dependable while at the same time being compatible with different uses and connection equipment. 
     The attachment device according to the invention is characterized in that a closing part is designed to close said space performing partial take-up of the tractive forces, said closing part comprising a removable fixing screw extending in substantially parallel manner to the central pivot-pin in the closed state. 
     According to an example embodiment, the closing part is composed of a spacer through which the fixing screw passes, the assembly being able to be dismantled. 
     The bottom of the hook preferably presents a rounded shape arranged in such a manner that application of a tensile load takes place in the direction of the axis of rotation of the swivel. 
     Such a device presents compact dimensions with a closing system that is resistant and permanently visible, thereby giving the latter an enhanced dependability. 
     According to one feature of the invention, the hollow base of one of the rings comprises an annular positioning surface collaborating with a rim of the other ring while leaving a predefined clearance for free rotation of the rings. The base of the ring is provided with a housing for receiving a bearing which is inserted between the head of the pivot-pin and the rim of the other ring. 
     The closing parts can naturally be formed by simple bolts extending in substantially parallel direction to the central pivot-pin. The end surfaces of the hook are advantageously parallel and extend substantially orthogonally to the axis of rotation. 
     According to a first embodiment, the two rings are openable by means of two screws having opposite tightening and loosening directions in the axial direction of the axis of rotation. 
     According to a second embodiment, only one of the rings is openable, the other not being provided with a closing part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages and features will become more clearly apparent from the following description of an embodiment of the invention given for non-restrictive example purposes only and represented in the appended drawings, in which: 
         FIG. 1  is a perspective view of the swivel attachment device according to the invention with two openable rings; 
         FIG. 2  shows an exploded view of the device of  FIG. 1 ; 
         FIG. 3  represents a cross-sectional view of  FIG. 1 ; 
         FIG. 4  illustrates an exploded perspective view of the top ring after the spacer has been removed from the lateral space; 
         FIGS. 5 and 6  are similar views to  FIGS. 1 and 2  of an alternative embodiment with a single openable ring. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIGS. 1 to 3 , a swivel attachment device, denoted by the general reference numeral  10 , comprises a pair of rings  11 ,  12  able to rotate freely with respect to one another around a common axis of rotation  13 . The two rings  11 ,  12  are made for example from aluminium alloy or from any other metallic material. 
     Each ring  11 ,  12  is composed of a C-shaped open hook and a closing part designed to close the lateral space  16 ,  17  of the corresponding hook. Each closing part for example comprises a spacer  14 ,  15  through which a fixing screw  20 ,  23  passes. Space  16 ,  17  is arranged between the two flat and parallel end surfaces  11   a ,  11   b ;  12   a ,  12   b  of the hook to enable insertion of a strap loop or a rope in ring  11 ,  12  after the corresponding closing part has been removed. 
     In  FIG. 4 , one of the surfaces  11   a  of top ring  11  is provided with a first threaded blind hole  18 , and the other surface  11   b  of the same ring  11  is provided with a second hole  19  that is pass-through and not threaded. The two holes  18 ,  19  are aligned substantially in a direction parallel to the axis of rotation  13  to enable a screw  20  to pass through. 
     The whole of this assembly can be inclined with respect to the axis of rotation  13  to improve the shape or the space occupation of the swivel. 
     The same is the case for the other bottom ring  12  which is inverted with respect to first ring  11 . Surface  12   a  is provided with a third threaded blind hole  21 , and the other surface  12   b  is equipped with a fourth hole  22  that is pass-through and not threaded. The two holes  21 ,  22  are aligned substantially in a direction parallel to the axis of rotation  13  to enable another screw  23  to pass through. 
     Spacer  14 ,  15  of each closing part has a substantially cylindrical shape, and has a bore  24 ,  25  axially drilled therein for passage of screws  20 ,  23 . The axial length of the spacer corresponds to the interval of lateral space  16 ,  17 , and the diameter of the bore  24 ,  25  is slightly larger than that of screws  20 ,  23 . 
     The base of top ring  11  comprises an annular housing  26  designed for fitting a ball-bearing or rollers  27 . The bottom end of the base is open delineating an annular positioning surface  28 . 
     The top of bottom ring  12  is equipped with a rim  29  which fits into annular positioning surface  28  for axial centring of the two rings  11 ,  12 . A pivot-pin  30  is used to constitute the axis of free rotation  13  of the two rings  11 ,  12 . Head  31  of pivot-pin  30  presses on the bearing cage  27 , and its shank  32  passes through bearing  27  and is secured in an aperture  33  of ring  12 . The assembly formed by bearing  27  and pivot-pin  30  is configured so as to leave a clearance J of small thickness between the base and the top of the two rings  11 ,  12  to enable rotational movement thereof in both directions. 
     Preferably, the two spacers of closing parts  14 ,  15  are made from metallic material and are arranged to avoid any dangerous catching points inside rings  11 ,  12 . They can have a coating of different hook. A single screw  20 ,  23  is necessary to close each ring  11 ,  12 , and the corresponding spacer remains perfectly visible from the outside in the assembled position. The strap loop or rope remains captive in ring  11 ,  12  with total safety, while at the same time remaining angularly mobile due to the rounded or continuous inner surfaces. 
     When the swivel is tensioned, these strap loops or the rope automatically position themselves in the rounded hollow of hook  11 ,  12  coinciding with the axis of rotation  13  of the swivel assembly. 
     To open one of the rings  11 ,  12 , the corresponding screw  20 ,  23  simply has to be unscrewed by means of a spanner (not represented), and spacer  14 ,  15  be removed to release lateral space  16 ,  17 . It is then possible to replace one rope loop by another, or by any other attachment means. 
     The two screws  20 ,  23  extend in substantially parallel manner to the axis of rotation  13  of pivot-pin  30 , and are fitted in the reverse direction to one another for fixing of the two closing parts  14 ,  15 . 
     It is clear that screws  20 ,  23  and spacers  14 ,  15  can be replaced by bolts or any other removable fixing means designed for partial take-up of tractive forces. Screws  20 ,  23  can also be inclined with respect to axis of rotation  13  without departing from the scope of the invention. 
     In the alternative embodiment of  FIGS. 5 and 6 , only one of rings  11  is openable. Swivel attachment device  100  is similar to that  10  of the previous figures, but ring  12  is totally closed being devoid of any lateral space  17  and of its spacer. The same reference numerals will be used to denote identical or similar parts. Ring  11  is identical to the one described in the foregoing.