Abstract:
An electrically weldable spring hinge comprising a housing having a cavity, in particular a cylindrical recess, into which cavity a hinge element can be inserted. A supporting body can be inserted into the cavity to block deformation of the housing at a location along the housing where electrical welding is performed. The hinge element may include a spring in the recess and the supporting body may be on the spring.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to an electrically weldable spring hinge including a housing with a cavity therein for receiving a hinge element. 
   Spring hinges of this type are known. They are used as hinges for ear pieces of spectacles and are fastened to the ear pieces of the spectacles by means of an electric welding process. During the electric welding, the spring hinge is pressed firmly against an ear piece of the spectacles. The applied pressure is within a range of, for example, 70 to 700 N. As soon as the pressure forces are applied, a welding current of 2000 A to 8000 A is conducted via the housing and the ear piece. Welding projections are provided in the contact region between the spring hinge and the ear piece of the spectacles, which heat up and melt at the high currents. This produces a firm connection between the spring hinge and the earpiece of the spectacles. It has been found that, at the high pressure forces, deformation of the housing of the spring hinge, in particular of the cavity provided inside the housing, may occur. This cavity accommodates a hinge element. The latter is displaced inside the cavity during use of the spring hinge. During the electric welding, material displacements which impair optimum functioning of the spring hinge may also occur: it is possible for material to be displaced into the interior of the housing, namely into the cavity, so that a protrusion is produced there. If deformation of the housing and thus of the cavity takes place or if material is displaced into the cavity during the welding, the mobility of the hinge element relative to the housing is impaired and thus the functioning of the spring hinge is impaired. Such deformations of the housing occur in particular in small spring hinges, which are being increasingly used. 
   SUMMARY OF THE INVENTION 
   The object of the invention is therefore to provide a spring hinge of the type mentioned at the beginning which, despite very small dimensions, can be attached to an ear piece of spectacles in an optimum manner in an electric welding process. 
   To achieve this object, a spring hinge is proposed which is distinguished by the fact that the housing of the spring hinge has a cavity into which a supporting body can be inserted at least during the electric welding. This offers the advantage that the supporting body prevents undesirable material displacements caused by the electric welding process and that the supporting body stabilizes the housing during the welding and ensures an optimum flow of force. 
   A preferred embodiment of the spring hinge which is distinguished by the fact that the supporting body is designed as a separate part and can be removed from the cavity. This permits repeated use of the supporting body in the production process. 
   A further preferred exemplary embodiment is distinguished by the fact that the supporting body is part of a hinge element which can be inserted into the housing. This permits the smallest possible dimensioning of the cavity and thus of the spring hinge and saves two process steps during the production process, namely the insertion and removal of the supporting body. 
   A further preferred exemplary embodiment is distinguished by the fact that the supporting body is part of a spring element of the hinge element. In addition to a compact design of the spring hinge, this permits a simple construction with few parts and thus efficient manufacture of the spring hinge. 
   A further preferred exemplary embodiment is distinguished by the fact that the supporting body is designed as a guide element for the hinge element. In this case, a part of the spring hinge which is required anyway is designed in such a way that it additionally fulfills the function of the supporting body, a factor which ultimately reduces the number of individual parts of the spring hinge and thus permits cost-effective manufacture. 
   A further preferred exemplary embodiment is distinguished by the fact that the spring hinge can be attached to an ear piece of spectacles by means of an electric welding process. This permits a fixed connection between the spring hinge and the ear piece of the spectacles, which connection can be readily automated and can be carried out at defined temperature conditions. 
   A further preferred exemplary embodiment is distinguished by the fact that the housing of the spring hinge has at least two welding projections. This offers the advantage that, on account of the dimensioning and positioning of the welding projections, the welding currents and thus the flow behavior and the softening of the material can be established exactly. 
   A further preferred exemplary embodiment is distinguished by the fact that the supporting body is arranged in the region of a welding projection. Thus the applied pressure introduced via the welding projection and required for the welding can be absorbed by the supporting body and undesirable deformations of the housing of the spring hinge can also be prevented as a result. 
   A further preferred exemplary embodiment is distinguished by the fact that the hinge element can be inserted as a pre-assembled unit into the housing. This offers the advantage of an optimized and efficient manufacturing process. 
   A further preferred exemplary embodiment is distinguished by the fact that the spring hinge has a bead and/or latching elements for fixing the hinge element in the housing. In the production process, either the hinge element is inserted into the housing and latched there and/or the hinge element is inserted into the housing and fixed there by means of a bead to be incorporated. This offers the advantage of simple-to-produce and reliable fixing of the hinge element in the housing of the spring hinge. 
   A further preferred exemplary embodiment is distinguished by the fact that the bead is surrounded by a welding projection. This offers the advantage that the welding projection and the bead can be provided on the housing in the immediate vicinity of the supporting body. 
   A further preferred exemplary embodiment is distinguished by the fact that the supporting body has a groove and advantageously remains in the cavity of the housing. This offers the advantage that the bead can engage in the groove for fixing the supporting body. 
   A further preferred exemplary embodiment is distinguished by the fact that material displaced in a defined manner during the electric welding process fixes the hinge element in the housing. This offers the advantage that no latching elements or beads need be provided during the manufacturing process of the individual parts of the spring hinge, since the deformations occurring due to the welding process fulfill this function. 
   A further preferred exemplary embodiment is distinguished by the fact that the material displaced during the electric welding process engages in the groove of the supporting body. This offers the advantage that the supporting body is fixed in the housing during the process step of the welding and can serve as a stop for the spring element. 
   A further preferred exemplary embodiment is distinguished by the fact that the housing can be produced by means of MIM technology (Metal Injection Molding). In the MIM technology, relatively complicated shapes of the housing of the spring element can be realized in a similar manner to an injection molding process. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in more detail below with reference to the drawing, in which: 
       FIG. 1  shows a longitudinal section of a housing with supporting body; 
       FIG. 2  shows a plan view of the end face of the housing; 
       FIG. 3  shows a plan view of the end face of the housing in the welded state with an ear piece of spectacles; 
       FIG. 4  shows a further exemplary embodiment of the housing in the same view as  FIG. 2 ; 
       FIG. 5  shows a housing as in  FIG. 4  in the welded state with an ear piece of spectacles; 
       FIG. 6  shows a partial longitudinal section of a spring hinge; 
       FIG. 7  shows a bottom view of the spring hinge shown in  FIG. 6 ; 
       FIGS. 8  to  10  show further exemplary embodiments of the spring hinge shown in  FIG. 6 ; 
       FIG. 11  shows a bottom view of the spring hinge shown in  FIG. 10 , and 
       FIGS. 12  to  14  show further exemplary embodiments similar to the spring hinge shown in FIG.  6 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a longitudinal section of a spring hinge  1  for spectacles, having a housing  2  and a supporting body  3 . It can be seen that the housing  2  has a cavity, which is designed here as a cylindrical recess  5  into which the supporting body  3  can be inserted. The housing  2  comprises a first welding projection  9  and a second welding projection  11  which serve to electrically weld the housing  2  to an ear piece (not shown here) of spectacles. During the welding, forces which are indicated by two arrows  13 ,  13 ′ occur at the welding projections  9  and  11 . Depending on the design of the housing  2 , the forces could lead to an undesirable deformation of the housing  2 . It can be seen that the supporting body  3  is inserted into the housing  2  in the region of the first welding projection  9 . That force acting during the welding which is indicated by the arrow  13  is therefore transmitted via a housing wall  15  directly to the supporting body  3 . Undesirable deformations of the housing  2  in the region of the housing wall  15  are thus virtually ruled out. Adjoining the end of the recess  5  is a supporting region  17  which is made of solid material and serves to absorb those forces transmitted during the welding which are indicated by the arrow  13 ′. The supporting body  3  and the supporting region  17  thus give the housing  2  the necessary stability for the welding process. After the welding operation, the supporting body  3 , which is fastened here to a rod  19 , can be removed from the recess  5  by means of the rod  19 . A hinge element can thus be put into the recess  5  after the welding. 
     FIG. 2  shows a plan view of the end face of the housing  2 . The same parts are provided with the same reference numerals, so that reference is made to the description relating to FIG.  1 . 
   The supporting body  3  with the rod  19  can be seen, the supporting body  3  being located in the cylindrical recess  5  in the region of the first welding projection  9  and a further first welding projection  9 ′. It can also be seen that the housing  2  is a closed housing which has only one opening, which is formed by the recess  5 . 
     FIG. 3  shows the housing  2  as in  FIG. 2  with the difference that it is welded to an ear piece  21  of spectacles. Material displaced during the welding can be seen, this material, in the form of bulges  23 , being located laterally at the transition  25  between the housing  2  and the ear piece  21  of the spectacles. The supporting body  3  bears against the inside of the housing wall  15  and supports the latter. In addition to the supporting function, this offers the advantage that material softened during the welding operation cannot pass into the recess  5 , so that malfunctions of the spring hinge are reliably avoided. On account of the supporting effect of the supporting body  3 , deformations of the inner surface of the recess  5  are virtually ruled out. 
     FIG. 4  shows a further exemplary embodiment of the housing  2  in the same view as shown in  FIGS. 2 and 3 . The same parts are provided with the same reference numerals, so that reference is made in this respect to the description relating to the preceding figures. 
   The essential difference from  FIG. 2  consists in the fact that a center welding projection  27  is provided instead of the first welding projections  9 ,  9 ′. On account of the arrangement of the supporting body  3  in the region of the center welding projection  27 , it is possible for the housing  2  to remain undeformed despite the forces which occur during the electric welding. Furthermore, it is ensured that material softened during the welding operation cannot pass into the cylindrical recess  5  and lead there to undesirable bulges. 
     FIG. 5  shows the housing  2  shown in  FIG. 4  of the spring hinge  1  with the ear piece  21  of the spectacles. The same parts are provided with the same reference numerals, so that reference is made in this respect to the description relating to the preceding figures. 
   The essential difference from  FIG. 3  consists in the fact that the welding operation causes no undesirable lateral bulges  23 . This is due to the fact that the welding projection  27  is arranged centrally, so that regions of the welding projection  27  which are softened by the welding operation cannot spread up to the outer surfaces of the housing  2 . That region of the housing wall  15  which lies in the center, in the immediate vicinity of the center welding projection  27  and of the supporting body  3 , is also softened during the welding operation. In this case, the supporting body  3  ensures that undesirable deformations of the inner surface of the cylindrical recess  5  are ruled out. 
     FIG. 6  shows a partial longitudinal section of a spring hinge  1  having a housing  2  and a hinge element  31  which projects into the cylindrical recess  5  of the housing  2  of the spring hinge  1  and is fixed there by means of a top bead  33  and a bottom bead  35 . The hinge element  31  essentially has a bearing body  39  having a hole  41  and a spring pin  43  having a spring element, designed here as a helical spring  45 , and a spring stop  47 . The spring stop  47  is firmly connected to the spring pin  43  of the hinge element  31  or is formed by this spring pin  43 , for example by shaping the end of the spring pin. The helical spring  45  is guided by the spring pin  43  and is located between the spring stop  47  and the top bead  33  and the bottom bead  35  of the housing  2 . The two beads  33  and  35  constrict the free interior space of the recess  5  in such a way that they act as a stop for the helical spring  45 . If a tensile force is exerted on the hinge element  31  during use of the spring hinge  1 , deformation of the helical spring  45  takes place in such a way that restoring forces are built up, and these restoring forces pull the hinge element or its spring pin  43  back into the interior of the recess  5 . In the representation according to  FIG. 6 , restoring forces acting to the right are thus exerted on the hinge element  31  by the helical spring  45 , so that the bearing body  39  forming a hinge lug is pulled against a bearing surface  49 , which is formed by the left-hand front side of the housing  2  of the spring hinge  1 . The basic function of the spring hinge  1  is known in principle, so that it is only dealt with briefly here: a center-part hinge, which is fastened to the center part of spectacles, is attached to the hinge element  31 , for example by means of a screw which passes through the hole  41 . When the ear pieces of the spectacles are swung out, the spring hinge  1  being attached to said ear pieces, tensile forces are exerted on the hinge element  31 , and the helical spring  45  counteracts said tensile forces. The center-part hinge has bearing surfaces which bear against the bearing surface  49  and ensure defined basic positions of the ear pieces relative to the center part. In this way, the ear pieces are held firstly in the swung-in position and secondly in the swung-out position by the spring hinge  1 . 
   The helical spring  45  has a reinforced region  51  which, in the exemplary embodiment shown here, consists of two blocked spring coils. The reinforced region  51  lies in the immediate vicinity of the welding projection  37 . The reinforced region  51  of the helical spring  45 , as supporting body  3 , thus counteracts undesirable deformations of the housing  2  during a welding operation. 
   In this exemplary embodiment, the welding projection  37  and a second central welding projection  11 ′ of the housing  2  have annular recesses  53  which run directly next to the welding projections  37 ,  11 ′ and serve to accommodate material displaced during the welding operation. That is to say that material softened and displaced during the welding operation is channeled by means of the recesses  53 . Thus the material softened during the electric welding is collected and bulges, as are explained with reference to  FIG. 2 , are avoided. 
     FIG. 7  shows a bottom view of the spring hinge  1  shown in FIG.  6 . The same parts are provided with the same reference numerals, so that reference is made in this respect to the description relating to the preceding figures. 
   The housing wall  15 , with the surrounding welding projection  37  and the second welding projection  11 ′, and the hinge element  31  with the hole  41  (indicated here by dotted line), can be seen in the bottom view. In this view, it becomes clear that the welding projection  37 , which surrounds the bead  35 , and the second welding projection  11 ′ are provided centrally on the housing wall  15  as viewed in the longitudinal direction. Located in the center of the welding projection  37  is the bottom bead  35 , which fixes the helical spring  45  and thus the hinge element  31  in the cylindrical recess  5  of the housing  2 . A groove  55 , in which the hinge element  31  engages, can be seen in the housing wall  15 . The groove  55  forms a sliding bearing and thus a guide for the hinge element  31 , this guide preventing rotation of the hinge element  31  about the center axis of the spring pin  43 . 
     FIG. 8  shows a further exemplary embodiment of the spring hinge  1  shown in FIG.  6 . The same parts are provided with the same reference numerals so that reference is made in this respect to the description relating to the preceding figures. 
   The essential difference from  FIG. 6  consists in the fact that the spring hinge  1  has a supporting body  3 ′ with a groove  57  open on one side. In this case, the supporting body  3 ′ serves as a guide for the spring pin  43  and as a spring stop for the helical spring  45 . On account of the spring forces of the helical spring  45 , the supporting body  3 ′ is pressed against the bottom bead  35 , which projects into the free interior space of the recess  5  and thus fixes the hinge element  31  in the recess  5  of the housing  2  via the supporting body  3 ′ and via the helical spring  45 . The functional principle, already described with respect to  FIG. 6 , of the spring hinge  1  is obtained on account of the spring forces of the helical spring  45 , which act on the one hand on the spring stop  47  and on the other hand via the supporting body  3 ′ and the bottom bead  35  on the housing  2 . 
   The supporting body  3 ′ thus runs against the bottom bead  35  in such a way that it is located in the immediate vicinity of the welding projection  37 . Thus, as already described beforehand, the supporting body  3 ′, during an electric welding operation, prevents undesirable displacements of material and possible deformations of the housing  1 . 
     FIG. 9  shows a further advantageous exemplary embodiment of the spring hinge  1 . The same parts are provided with the same reference numerals, so that reference is made to the description relating to the preceding figures. 
   A supporting body  3 ″ can be seen, this supporting body  3 ″, unlike the supporting body  3 ′, having an encircling groove  59  with two lateral boundary flanks. The bottom bead  35  of the housing  2  engages in the groove  59  and thus fixes the supporting body  3 ″ in the cylindrical recess  5  of the housing  2 . In this case, the supporting body  3 ″ is arranged in the cylindrical recess  5  of the housing  2  in such a way that it lies in the immediate vicinity of the welding projection  37 . The supporting body  3 ″ thus acts firstly—as already described—as a supporting body, secondly as a guide for the spring pin  43  and thirdly, by means of the encircling groove  59  and the bottom bead  35 , as fixing for the hinge element  31  in the housing  2 . 
     FIG. 10  shows a further exemplary embodiment of the spring hinge  1 . The same parts are provided with the same reference numerals, so that reference is made in this respect to the description relating to the preceding figures. 
   The central welding projection  27 —as viewed in the longitudinal direction of the housing  2 —and the likewise central welding projection  11 ′ can be seen. The top bead  33  of the housing  2  engages in the encircling groove  59  of the supporting body  3 ″. In this embodiment, it is especially advantageous that material of the housing wall  15  is displaced into the recess  5  of the housing  2  during the electric welding. In this case, the supporting body  3 ″ and the welding projection  27  are arranged in such a way that the displaced material of the housing wall  15  engages in the encircling groove  59  of the supporting body  3 ″. 
   In this exemplary embodiment, the material displaced into the recess  5  of the housing  2  serves as additional fixing for the supporting body  3 ″. This offers the advantage that the process step of incorporating the bottom bead  35  described with respect to the preceding figures can be omitted. If need be, the top bead  33  may also be dispensed with in this case, so that an operation—incorporating the bead  33 —is omitted. 
     FIG. 11  shows a bottom view of the spring hinge  1  shown in FIG.  10 . The same parts are provided with the same reference numerals, so that reference is made in this respect to the description relating to the preceding figures. 
   The central welding projection  27  and the second central welding projection  11 ′ can be seen. The central welding projection  27  has an elongated shape which runs transversely to the longitudinal direction of the housing  2  and which ensures a specific displacement of material into the groove  59  of the supporting body  3 ″ during the welding operation. 
   In particular, the following becomes clear: beads may be provided in order to fix the hinge element in the interior of the housing of the spring hinge. In this case, there may in each case be a single bead at the top and bottom, or else there may also be two beads, one at the top and one at the bottom. In addition to or instead of the beads, wall regions of the housing which have been deformed by the electric welding operation may be provided, these wall regions projecting into the recess in the housing and thus fixing the hinge element. The term “fixing” here is merely intended to mean that the hinge element cannot be pulled completely out of the housing. The free mobility of the hinge element must be retained in order to ensure the basic function of the spring hinge. When the hinge element is fixed, it is therefore merely ensured that an abutment is formed for the spring element designed as a helical spring. Thus the restoring forces produced when the hinge element is being pulled out can be built up. 
     FIG. 12  shows a further advantageous embodiment of the spring hinge  1  having a latching element  61 . The same parts are provided with the same reference numerals, so that reference is made in this respect to the description relating to the preceding figures. 
   Unlike the preceding exemplary embodiments, the housing  2  has a groove  63  which is open at the bottom and intersects the cylindrical recess  5  of the housing  2  at the top and bottom. As a result, steps  65  and  65 ′, in which the latching element  61  engages, are formed. The latching element  61  has an opening, through which the spring pin  43  passes. 
   In  FIG. 12 , the latching element  61  is in the latched state, that is to say in bearing contact with the steps  65 ,  65 ′, and forms a stop for the helical spring  45 . Here, the latching element  61  may at the same time serve as a guide for the spring pin  43  of the hinge element  31 . The hinge element  31  is held in the cylindrical recess  5  of the housing  2  via the latching element  61  by means of the spring forces, already described, of the helical spring  45 . 
   The spring hinge  1  has a supporting body  3 ′″ which is located in the immediate vicinity of the welding projection  9 . The exemplary embodiment shown here has four welding projections arranged in pairs, of which only the welding projection  9  and the welding projection  11  can be seen here. The supporting body  3 ′″ here serves as a guide for the spring pin  43  and thus for the hinge element  31  along the center axis of the guide rod  43  and serves to stabilize the housing  2  during a welding process. It can also be seen that the housing wall  15  is interrupted by the groove  63  and by the groove  55  and is thus open at the bottom. 
     FIG. 13  shows a further exemplary embodiment of the spring hinge  29  with the supporting body  3 ″ and the bottom bead  35 , which is arranged between the first welding projection  9  and the first welding projection  9 ′, which cannot be seen here. The same parts are provided with the same reference numerals, so that reference is made in this respect to the description relating to the preceding figures. 
   In this advantageous exemplary embodiment of the invention, four welding projections are provided on the spring hinge  1  for connecting to an ear piece of spectacles, of which welding projections the first welding projection  9  and the second welding projection  11  can be seen here. The bottom bead  35  is incorporated in the housing wall  15  of the housing  2  in such a way that it lies between the first welding projection  9  and the first welding projection  9 ′ (not shown here) lying in front of the cutting plane. The bead  35 , on the inside of the cylindrical recess  5  of the housing  2 , engages in the encircling groove  59  of the supporting body  3 ″, as a result of which the supporting body  3 ″ is fixed in the cylindrical recess  5  of the housing  2 . Thus the supporting body  3 ″—as already described—acts as a stop for the helical spring  45  and thus at the same time fixes the hinge element  31  in the housing  2  of the spring hinge  1 . 
   In addition to the fixing by the bottom bead  35 , material of the housing wall  15  of the housing  2  which has been softened and displaced during the welding can be displaced into the interior of the cylindrical recess  5 . In the exemplary embodiment shown here, the first welding projections  9 ,  9 ′, in a similar manner to the exemplary embodiment described in  FIG. 10 , are arranged in such a way that they are located in the immediate vicinity of the encircling groove  59  of the supporting body  3 ″. This means that the material displaced into the interior of the housing  2  engages in the groove  59  and thus fixes the supporting body  3 ″ in addition to the fixing of the latter by the bottom bead  35 . It becomes clear that, on account of the material displaced during the electric welding, the bead  35  may be readily dispensed with. 
     FIG. 14  shows a further advantageous exemplary embodiment of the spring hinge  29  having a latching element  61 ′. The same parts are provided with the same reference numerals, so that reference is made in this respect to the description relating to the preceding figures. 
   It can be seen that the groove  63  open at the bottom extends only up to about the center axis of the cylindrical recess  5  of the housing  2 . This results in the step  65 ′, in which the latching element  61 ′ engages. In the latched state, the latching element  61 ′ engages in the step  65 ′. In the process, it serves as a stop for the helical spring  45  and is pressed against a supporting region  67  of the housing  2  on account of the spring forces of the helical spring  45 . The latching element  61 ′ has a suitable opening (not shown here), through which the spring pin  43  passes, the latching element  61 ′ additionally bearing against the spring pin  43  and thus being stabilized. 
   On the basis of the examples shown here, it becomes clear that the shape and type and attachment of the supporting body may be varied. Thus it is conceivable to provide the supporting body on the hinge element  31 , to design it as a cube or to design it in any desired shape. However, the external shape of the supporting body is preferably adapted to the inner contour of the recess  5 . It is then also conceivable, instead of the cylindrical recess, to provide a rectangular recess or a cavity of any desired configuration in the housing of the spring hinge  1 . It is also possible to provide a plurality of insertable supporting bodies of any desired configuration and/or removable supporting bodies designed as a separate part for a plurality of welding projections. It is essential in this case that the supporting body is arranged in the region of welding projections and directs or influences material possibly displaced during a welding process in a desired manner and increases the stability of the housing of the spring hinge during the welding process and/or during subsequent use of the spring hinge. In addition, it is possible to provide any desired fixing elements, such as latching or spring elements, beads or the like, for fixing the hinge element in the housing and to apply the restoring forces for the hinge element by any desired spring elements, such as, for example, helical springs, meander springs, torsion springs or the like. 
   The housings  2  of the spring hinges  1  are preferably designed in such a way that the currents occurring during the electric welding are conducted through the housing  2  at a distance from the spring element, that is to say the helical spring  45  in this case. Excessive heating and weakening of the spring element is thus avoided, as is tacking of the helical spring  45  to the housing  2 . The currents can be influenced by different wall thicknesses of the housing  2 , but also by an electrically conductive supporting body being provided, as has been described here. This electrically conductive supporting body is then preferably arranged in the region of the welding projections in order to realize an especially low electric resistance here. The electric currents are thus conducted through the housing and the supporting body into the welding projections, which thus melt and provide the material required for the welding operation. It becomes clear that the welding projections can thus not only be arranged on the housing underside, which faces the ear piece, but can also be arranged on the ear-piece top side. The welding projections present on the ear piece can then interact with a spring hinge  1  to be attached, or with its housing. However, care is to be taken in this embodiment to ensure that the spring hinge is attached to the welding projections in such a way that the supporting body can reliably absorb the forces occurring during the electric welding. It is therefore found that the exemplary embodiments explained here with reference to the figures are to be preferred, because the welding projections can then be arranged exactly in the desired regions. 
   A common feature of all the exemplary embodiments shown here is that the hinge element may be designed as a pre-assembled module and inserted into the housing  2 .