Abstract:
A lifting ring for a load, comprising a carrying loop, a pivoting body and a smooth cylindrical pin, a peripheral groove being formed near the free end of this pin, and an expandable retainer ring being inserted in said groove. The pin is engaged and locked axially in a cylindrical housing integral with the body of the load, this cylindrical housing comprising a peripheral channel opposite the groove of the pin, in which the expandable retainer ring is inserted.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to lifting rings, especially for heavy loads.  
           [0002]    The lifting ring of the invention is more specifically intended for hanging loads requiring precise manoeuvres of positioning and orientation, such as industrial injection moulds, etc.  
         DESCRIPTION OF PRIOR ART  
         [0003]    Conventional pivoting lifting rings comprise a pivoting body supporting a shackle and an anchor element consisting of a threaded rod.  
           [0004]    Such rings are disclosed in particular in WO 90/10803 and GB 2 303 682.  
           [0005]    Practice reveals that these rings raise a series of problems. Their weak point (rupture zone) is not usually the ring but the junction between the threaded part and the bearing face where the ring is placed against the load. This observation is found to be true with one-piece rings as well as articulated rings (it becomes worse if the ring is not perfectly in contact with the bearing face).  
           [0006]    Besides this, users of tooling (particularly in the case of plastic injection moulds) often find the rings difficult to deal with as they leave little room for the lifting hook to be inserted, to such an extent that the various connectors, unions and pipelines become torn during handling, more especially when the handled parts are being turned over.  
           [0007]    There is therefore a real need to safely increase the distance between the point of application of the hook and the surface of the moulds, but also a separate problem of safety, because very often users will resort to ad-hoc arrangements and other hazardous solutions with rings mounted on extension pieces to provide more distance between the point of application of the hook and the bearing face of the load.  
         SUMMARY OF THE INVENTION  
         [0008]    The invention solves the above problems by providing rings with smooth shanks, with a retention system as set out in the technical report given below, and also makes possible, owing to the extra room achieved, the addition of a base whereby rings can have a large clearance combined with exceptional strength.  
           [0009]    The subject of the invention is a lifting ring for a load, comprising a carrying loop, a pivoting body and an element that anchors in the body of a load in which the anchor element is a smooth cylindrical pin. A peripheral groove is formed near the free end of this pin, and an expandable retainer ring is inserted in said groove. The pin is engaged and locked axially in a cylindrical housing integral with the body of the load by the retainer ring. The cylindrical housing comprises a second peripheral groove opposite the groove in the pin, in which the expandable retainer ring is inserted.  
           [0010]    The expandable retainer ring is preferably a split spring ring, or comprises a spring part exerting an outward force on rollers or segments so as to engage them in the channel.  
           [0011]    The loop may be an integral part of the body of the ring. Alternatively it passes through an eye incorporated in the body of the ring.  
           [0012]    In an advantageous embodiment, the cylindrical housing in which the pivoting body is mounted is formed in a base fixed to the body of the load.  
           [0013]    The top of this base may have a large clearance forwards of the surface of the load, thus facilitating hanging operations.  
           [0014]    If so, it is advantageous to have the cylindrical housing pass through the base.  
           [0015]    The cylindrical housing then advantageously comprises a section of larger diameter towards the back of the base, with an annular holder being inserted along this section, between the base and the pin, to keep the retainer ring or its components in place.  
           [0016]    The pin may project beyond the back of the base into a cavity of corresponding diameter formed in the body of the load, thus improving its centring and its retention.  
           [0017]    The invention also relates to a body for a lifting ring as described above, which comprises a loop, and a smooth cylindrical pin, a peripheral groove being formed near the free end of this pin and an expandable retainer ring being inserted in said groove.  
           [0018]    A clamping collar advantageously keeps the retainer ring compressed and in position before the smooth pin is inserted in an appropriate housing.  
           [0019]    One advantage of the invention is that the strength of the shank can be increased because, for example, a smooth pin with a diameter of 48 mm is stronger than an M 48 thread, especially at the junction with the ring. It is easy to increase strength by increasing the diameter from Ø48 to Ø56, which will increase the strength by about 1.8, thus offering a capacity for use in traction at 90° close to that of axial traction. As a rule, the loss of efficiency at 90° is of the order of 40% compared with axial traction, owing to the weakness at the point of junction with conventional rings in both one-piece and articulated designs.  
           [0020]    The cost of a smooth shank Ø56 is less than that of a threaded shank Ø48, despite the smaller diameter.  
           [0021]    Another advantage is that the invention solves the problem of tightening (or forgetting to tighten): a ring cannot only half snap or lock into position. Moreover, the capacity at the connection of the rod with the ring is reinforced.  
           [0022]    The lifting ring according to the invention gives the manufacturer guaranteed values, corresponding to the drive for standardization, particularly from the major customers in the plastics industry, but also in other industries. 
       
    
    
     SHORT DESCRIPTION OF THE DRAWINGS  
       [0023]    Other features and advantages of the invention will become clear in the following description of certain particular embodiments, reference being made to the appended drawings, in which  
         [0024]    [0024]FIG. 1 is a side view of one embodiment of the ring housed in a load (in cross section)  
         [0025]    [0025]FIGS. 2 and 3 are side views of an embodiment in which the loop is a different shape  
         [0026]    [0026]FIGS. 4 a  to  4   d  are sectional views of details of the embodiment of the locking system of the pin  
         [0027]    [0027]FIG. 5 is a side view of a ring with base  
         [0028]    [0028]FIGS. 6 and 7 are combined views in lateral cross section and from beneath, respectively, of a ring with base with an axial clearance  
         [0029]    [0029]FIG. 8 is a sectional side view of a ring as in FIG. 6, with a lengthened pin. 
     
    
       [0030]    The figures are not drawn to scale. Generally, identical components are denoted by the same reference numerals in the figures.  
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0031]    [0031]FIG. 1 is a general view of the lifting ring of the invention composed of a carrying loop  2  which here forms one piece with the pivoting body  4 . This body  4  is extended rearwards by a smooth pin  6 .  
         [0032]    The axes x and y define the directions of the lateral and axial stresses.  
         [0033]    A peripheral groove  8  is formed in this pin  6 , generally near the free end.  
         [0034]    The pin  6  is inserted into a cylindrical housing  10  in the body of the load  12 . A channel  14  encircles the cylindrical housing  10  at a depth from the plane of the surface  16  of the load  12  corresponding to the position of the groove  8  on the pin  6 .  
         [0035]    An expandable retainer ring  18  is placed in the groove of the pin  6 . Here, the retainer ring  18  is a split spring-steel ring  19  treated to make it hard and with a profile designed to assist insertion and avoid the risk of closing up on itself during use.  
         [0036]    Prior to insertion, the retainer ring  18  is kept compressed by a clamping collar (not shown). When the pin  6  is pushed into the cylindrical housing  10 , the retaining ring  18 , which is slightly conical, begins to enter this housing  10  because of its elasticity. The clamping collar slides back and, once the retainer ring is inside the housing  10 , can be withdrawn. The ring  1  is then simply pushed fully into its housing  10  until the retainer ring, arriving level with the channel  14 , relaxes into it and so locks the ring  1 .  
         [0037]    The respective positions of the channel and groove are calculated to give the bearing face  20  of the ring  1  sufficient play to permit free rotation of the ring  1  relative to the body of the load  12 .  
         [0038]    The diameter of the smooth pin is of course calculated in such a way that even its thin part still has sufficient strength under axial tension.  
         [0039]    [0039]FIGS. 4 a  to  4   d  show in further detail a number of different possible embodiments of the expandable retainer ring. FIG. 4 a  shows the split spring ring  19 .  
         [0040]    When the diameter of the pin is small, the split ring  19  may not have sufficient elasticity. In this case a leaf spring  22 , wound into a spiral of more than one revolution, is used, as shown in FIGS. 4 b,    4   c  and  4   d.  This leaf  22  is positioned underneath rollers  24  (FIGS. 4 b,    4   c ) or segments  26 , which it pushes outwards. To prevent any return towards the centre, the development of the leaf  22  is calculated so that its extremities come end to end after expansion. The rollers  24  or segments  26 , engaged and held in the bottom of the channel  14 , are made of very hard steel and work in shear in the case of axial tension.  
         [0041]    [0041]FIGS. 2 and 3 show that the ring may, without departing from the scope of the invention, have loops  2  of various forms.  
         [0042]    In FIG. 2, the loop  2  is in the form of a closed hoop  28  passing through an eye  30  incorporated in the body  4  of the ring. Traction can occur in any direction between x and y.  
         [0043]    In FIG. 3, an intermediate link  32  is fitted between the eye  30  and the closed hoop  28 . The hoop  28  can be oriented and hooked in the appropriate direction so that a hook swings in a plane parallel to the bearing face  16 .  
         [0044]    If the body of the load is thin-walled, it may be difficult or even impossible to insert the pin directly into it. In this case the cylindrical housing  10  is formed in a base  33 , which in turn is fixed either directly to the wall of the load, or to the back of the wall, as shown in FIG. 5.  
         [0045]    [0045]FIGS. 6, 7 and  8  show an embodiment in which the loop, mounted on a base  34 , has a large clearance away from the bearing face of the load.  
         [0046]    This embodiment is made possible by the great strength conferred by the smooth pin and by the gain in axial extension, due to the absence of any loop pivoting mechanism, since the body of the ring  1  is itself able to pivot.  
         [0047]    Despite the large bending moment created by the clearance of the ring, the unit still has high strength.  
         [0048]    The top views (FIG. 7) illustrate the possibility of making bases  34  with a large spread, bolted to the bearing face of the load. As shown, the bearing plate  6  of the base  34  may, depending on the total dimensions desired, be round or square in shape.  
         [0049]    The pin  6  is retained either by a split retaining ring  18  or by rollers  24 , or by very hard steel segments  26  working in shear.  
         [0050]    The cylindrical housing  10  may, as shown in FIG. 6, pass through the entire length of the base  34  and include a larger-diameter section  40 , which enables an annular holder  40  to be inserted through the back of the base  34  to keep the retainer ring  18  or its components (rollers  24 , segments  26 ) in place.  
         [0051]    In FIG. 8, the ring with base is bolted down over a cavity formed in the body of the load. The diameter of this cavity is calculated so that a centring ring  44  can be inserted to give additional safety in the case of traction in the direction y.  
         [0052]    It will be observed that the cavity may be a tapped hole in the base  34 , thus allowing a conventional lifting ring to be secured in the same position if desired.  
         [0053]    The ring and its tail are made in one piece forming a compact monolithic unit.  
         [0054]    The clearance base is fixed to the load in such a way that it cannot pivot and in such a way as to form a whole integral with the load, creating a new bearing force taking the place of the initial offset force.