Abstract:
The invention concerns an elastic hinge for specticles frame comprising two fixed ( 5 ) and mobile ( 7 ) hinge elements, articulated about an axis of rotation (R) by a pivoting head ( 7 A) of one ( 7 ) of the elements inserted in a pivoting head ( 5 A) of the other element ( 5 ) and by a link ( 9 ) housed in succession in an inner passage ( 5 D,  7 D) of the two elements emerging into the pivoting heads. The invention is characterized in that each pivoting head ( 5 A,  7 A) has at the opening of the passage ( 5 D,  7 D) a stop member (B 1,  B 2 ) on the outer side of the frame forming by the matching shape of one (B 1 ) with the other (B 2 ) a pivoting interface about a second axis of rotation (R′), the link ( 9 ) being arranged between the two axes of rotation (R, R′) when the bow is in a normal opening position. The hinge has two stable closing and opening positions as well as an additional unstable opening position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of International Application PCT/IB00/00932 filed Jul. 10, 2000, which claims priority of French Patent Application No. 99.09299 filed Jul. 13, 1999. International Application PCT/IB00/00932 was published in French under PCT Article 21(2) and is now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an elastic spectacle-frame hinge, and more particularly to a hinge which comprises two elements, a fixed element and a mobile element, which are connected to a front and to a side-piece of the frame respectively. 
     The two elements are articulated in relation to one another about an axis of rotation by a pivoting head on one of the elements, which head is inserted in a pivoting head on the other element, and by a link which is disposed inside two elements and passes successively through the pivoting heads. 
     2. Description of the Related Art 
     A hinge of this type is known, in particular, from Patent Application FR 2 698 121, which was published on May 20, 1994. The pivoting heads are spherical in shape and pivot about an imaginary axis passing through the centre of the two spheres. 
     The two hinge elements are perforated by an internal duct so as to permit the successive passage of a strand which is anchored in each duct by one end. The tensile force exerted by the fixed element on the mobile element is proportional to the deformation of the strand in the event of the latter being, by nature, elastic. If the strand is non-extensible, the tensile force is proportional to the deformation of a spring mounted between the mobile element and the point at which the strand is anchored. 
     When the side-piece of the frame is in the normal opening position, the strand extends parallel to the direction of axial alignment of the two elements, while at the same time being offset in relation to the axis of rotation on an outer side of the frame. “Outer” is understood to mean the region which is not contained between the front and the two side-pieces in the normal opening position. Conversely, the region contained between the front and the two side-pieces forms the inside of the frame. 
     When the frame is closed, the strand is offset progressively from one side to the other in relation to the axis of rotation. The tensile force generates a return torque which is cancelled when the middle fibre of the strand passes vertically across the axis of rotation. This results in a bistable effect which ought to endow the hinge with a closing position and a normal opening position which are stable. 
     It is found to be the case, however, that nothing permits the opposing of the tensile force in the normal opening position, in which the strand is straight. Being offset outwards in relation to the axis of rotation, the strand exerts, on the mobile element, a torque which leads to pivoting of the side-piece towards an extra opening position. 
     In other words, in the known hinge, although the bistable effect leads to a stable closing position, it seems to lead, on the other hand, not to a stable normal opening position, but in fact to a stable over-opening position. It is clear that a situation of this kind does not make the frame comfortable to use, and reduces its stability when worn. 
     BRIEF SUMMARY OF THE INVENTION 
     One of the objects of the invention is to improve a type of elastic hinge by using a link to join together the elements connected to the front and side-piece, so as impart a stable character to the closing and normal opening positions, and an unstable character to the extra opening position. 
     To that end, the subject of the invention is an elastic spectacle-frame hinge comprising two hinge elements, a fixed element and a mobile element, which are connected to a front and to a side-piece of the frame respectively and are articulated in relation to one another about an axis of rotation by a pivoting head on one of the elements, which head is inserted in a pivoting head on the other element, and by a link which is successively accommodated in an internal duct in the two elements which opens into the pivoting heads and is offset, in relation to the axis of rotation, from an inner side to an outer side of the frame when the side-piece pivots, in relation to the front, from a closing position to a normal opening position, characterised in that each pivoting head possesses a stop at the mouth of the internal duct on the outer side of the frame, which stops form, as a result of complementarity of shape of one with the other, an interface for pivoting about a second axis of rotation, the link being disposed between the two axes of rotation when the side-piece is in the normal opening position. 
     When the side-piece is in the normal opening position, the two complementary stops make it possible to neutralise the torque that tends to make the side-piece pivot outwards into an over-opening position. In other words, the normal opening position is a stable position. 
     The stops are arranged, as a result of complementarity of shape at a pivoting interface, so as to enable the side-piece to pivot from the stable normal opening position to an extra outward opening position. In the course of over-opening, the pivoting heads move apart from one another and the male and female knuckles reduce their contact surface. 
     The stops are formed at the mouth of the duct on the outer side of the frame so that the link passing successively through the pivoting heads remains offset inwards in relation to the second axis of rotation. In this way, the tensile force of the link creates a torque for returning the side-piece that tends to oppose the pivoting of the latter into over-opening. This return torque is counterbalanced only when the pivoting heads are inserted in one another again and when the male knuckles are in contact with a guide surface connecting the two female knuckles, that is to say in the normal opening position. In other words, the over-opening position is unstable. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages of the invention will become apparent on reading the description of a mode of embodiment which is illustrated by the drawings. 
     FIG. 1 is a view, in longitudinal section, of a side-piece belonging to a spectacle frame, which side-piece is articulated on a front lug by a hinge according to the invention. 
     FIG. 2 a  shows, in the longitudinal sectional plane in FIG. 1, a hinge element which is connected to the front. 
     FIG. 2 b  is a top view of FIG. 2 a.    
     FIG. 3 a  shows, in the longitudinal sectional plane in FIG. 1, a hinge element which is connected to the side-piece. 
     FIG. 3 b  is a top view of FIG. 3 a.    
     FIG. 4 a  is a view, in longitudinal section, of the hinge in FIG. 1 when the side-piece is in the normal opening position, that is to say substantially perpendicular to the front of the frame. 
     FIG. 4 b  is a view, in longitudinal section, of the hinge in FIG. 1 when the side-piece is in the closing position, that is to say substantially parallel to the front. 
     FIG. 4 c  is a view, in longitudinal section, of the hinge in FIG. 1 when the side-piece is in the extra opening position, that is to say substantially oblique towards the outside of the frame vis-à-vis the front. 
     FIG. 5 is a graph indicating effort as a function of the angular position of the side-piece vis-à-vis the front and comparing an ordinary hinge with a hinge according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the rest of the description, an identical element bears an identical reference in the various figures. 
     The elastic hinge according to the invention is intended for any spectacle frame which comprises, in known manner, two lenses connected to one another by a bridge to form a substantially flat front, and two lateral side-pieces which are each articulated on the front by a hinge. Represented in FIG. 1 is a side-piece  3  of the frame, which side-piece is articulated on a front lug  1  by a hinge  10 . The lug is bent practically at right angles, so that it has a longitudinal direction L which is substantially perpendicular to the front, which is not represented. 
     The lug is perforated in the longitudinal direction L by a blind hole, so as to accommodate therein a fixed hinge element  5  which is connected to the front. The side-piece  3  is likewise perforated by a blind hole in a direction substantially parallel to the side-piece, so as to accommodate therein a mobile hinge element  7  which is connected to the said side-piece. The two hinge elements each have a pivoting head  5 A,  7 A which tops an intermediate body  5 I,  7 I and a cylindrical body  5 B,  7 B. The latter extends in an axial direction A 1 , A 2 . 
     The cylindrical body  5 B of the fixed hinge element  5  is inserted in the blind hole in the front lug  1  until it abuts against the latter via a projection  5 C. The cylindrical body  7 B of the mobile hinge element  7  is likewise inserted in the blind hole in the side-piece  3  until it abuts against the latter via a projection  7 C. The heads  5 A and  7 A consequently project in relation to the blind holes in the front lug  1  and side-piece  3  in which the hinge elements are accommodated. 
     The pivoting head  7 A of the mobile hinge element  7  comprises—FIGS. 3 a - 3   b —two identical, cylindrical male knuckles  7 E which extend parallel and in a symmetrical manner in relation to the axial direction A 2  of the said hinge element. The two knuckles  7 E are inscribed, over a sector with an angle α of about 230 degrees, in a diagram cylinder whose axis constitutes an axis of rotation R 2  of the hinge element  7 . 
     The pivoting head  5 A of the fixed hinge element  5  possesses—FIGS. 2 a - 2   b —two identical female knuckles  5 E which extend parallel and in a symmetrical manner to the axial direction A 1  of the said hinge element. The two female knuckles are connected by a guide surface S which forms the bottom of a cavity which is open on the side opposite the intermediate body  51 . The guide surface S follows, over a sector with an angle β of about 150 degrees, the lateral wall of a diagram cylinder whose axis constitutes an axis of rotation R 1  of the hinge element  5 . 
     The two hinge elements  5  and  7  are each perforated by an internal duct  5 D,  7 D which extends in the axial direction A 1 , A 2  of the cylindrical body  5 B,  7 B and which opens into the head  5 A,  7 A of the hinge elements. The internal ducts are intended to accommodate a link passing successively through the hinge elements and the male and female knuckles so as to join them to one another like a pivot. 
     The guide surface S—FIG. 2 a —is set off towards the inside of the frame in relation to the duct  5 D. In other words, the axis of rotation R 1  is offset inwards in relation to the axial direction A 1  of the duct  5 D. The two male knuckles  7 E are likewise set off—FIG. 3 a —towards the inside of the frame in relation to the duct  7 D. In other words the axis of rotation R 2  is offset inwards in relation to the axial direction A 2  of the duct  7 D. As will be indicated further on, the axis of rotation R 2  merges with the axis of pivoting of the side-piece between the closing position and the normal opening position. 
     As illustrated by FIG. 4 a , at the hinge element  5  connected to the front, the link  9  is crimped in a cylindrical socket  11  which possesses a diameter substantially equal to that of the cylindrical body  5 B and against which the said socket abuts. At the mobile hinge  7 , the link  9  is crimped in a cylindrical socket  13  which possesses a diameter substantially equal to that of the cylindrical body  7 B. 
     In the mode of embodiment chosen to illustrate the invention, the link  9  is flexible and non-extensible, that is to say is able to follow a curve without becoming significantly longer compared to its straight length when at rest. In this case, the link  9  is threaded inside a helical spring  15  before being crimped in the cylindrical socket  13  at the hinge element connected to the side-piece. The length of the link between the two sockets  11  and  13  is chosen so as to force the helical spring  15  to become compressed. As a result of this arrangement, the spring abuts, on the one hand, against the cylindrical body  7 B and, on the other, against the cylindrical socket  13 . According to another mode of embodiment of the invention, which is not illustrated in the drawings, the link is, by nature, elastic, that is to say lengthens in a manner proportional to a tensile force exerted at one of its ends. In this case, the cylindrical socket  13  at the mobile hinge element abuts directly against the cylindrical body  7 B, the link being stretched between the two sockets, compared with its length when at rest. The intention is still to fit a spring, even with a link which is, by nature, elastic. 
     When the two knuckles are joined together with the aid of the link, the head  7 A of the side-piece knuckle is inserted in the head  5 A of the front knuckle. At the same time, the male knuckles  7 E come into contact with the guide surface S of the head  5 A, by inserting themselves between the female knuckles  5 E. The distance between the two female knuckles  5 E is slightly greater than the distance between the two male knuckles  7 E in order to permit insertion. The radius of the guide surface S is the same as the radius of the cylindrical male knuckles  7 E, so that the axes of rotation R 1  and R 2  of the female and male knuckles coincide. The guide surface S thus allows the mobile hinge element  7  to pivot, in relation to the fixed hinge element  5 , about an axis of rotation R which designates the axis of rotation R 1  or the axis of rotation R 2 , without distinction. 
     When the frame is assembled—FIG.  1 —the two hinge elements  5  and  7  are first of all joined together by inserting the link  9  and by crimping the latter in the sockets  11  and  13 , after threading the said link into the helical spring  15 , in the case of a non-extensible link. The two elements which have been joined together are then in the condition illustrated in FIG. 4 a . The hinge element  5  and the cylindrical socket  11  are then inserted, together, in the blind hole in the front lug  1 , and the hinge element  7 , the helical spring  15  and the cylindrical socket  13  are inserted, together, in the blind hole in the side-piece  3 . The hinge elements are interlocked with the lug and side-piece, for example by bonding or force fitting. 
     FIG. 4 a  illustrates a normal opening position of the side-piece in relation to the front of the frame. In this position, the hinge elements  5  and  7  are in alignment, that is to say the axial directions A 1  and A 2  coincide with one another in a single axial direction A. The link  9  is straight and parallel to the axial direction A. 
     FIG. 4 b  illustrates a closing position of the side-piece in relation to the front of the frame. In this position, the two hinge elements are at right angles, that is to say their axial directions A 1  and A 2  are substantially perpendicular. The link  9  is curved in the region of insertion of the pivoting heads  5 A and  7 A so as to follow the change in direction of the axial directions A 1  and A 2 . 
     In order to open or close the side-piece of the frame, the mobile hinge element connected to the said side-piece pivots about the axis of rotation R in relation to the fixed hinge element connected to the front. The region contained between the front and the two side-pieces is referred to, by convention, as the “inside” of the frame. In this way, closure corresponds to rotation of the side-piece towards the inside of the frame, and opening, to rotation towards the outside. 
     When the side-piece pivots from the normal opening position—FIG. 4 a —into the closing position—FIG. 4 b —the link  9  is offset from an outer side to an inner side in relation to the axis of rotation R. The return torque created by the tensile force of the link is cancelled when the middle fibre of the link is plumb with the axis of rotation. This results in a bistable effect which tends to return the side-piece to the closing position or to the normal opening position, according to whether the link is on the inside or outside in relation to the axis of rotation. 
     When the side-piece is in the normal opening position—FIG. 4 a —the middle fibre of the link  9  extends parallel to the common axial direction A, and is offset towards the outside of the frame in relation to the axis of rotation R. The hinge element  5  then exerts on the hinge element  7 , via the link  9 , a tensile force which creates a torque that tends to cause the side-piece to pivot outwards into an over-opening position. 
     According to the invention, the female pivoting head  5 A possesses, at the mouth of the duct  5 D, a stop B 1  which forms, as a result of complementarity of shape with a stop B 2  at the mouth of the duct  7 D in the pivoting head  7 A, an interface for pivoting about a second axis of rotation R′. The stops B 1  and B 2  are formed on the outer side of the frame. 
     When the side-piece is in the normal opening position—FIG. 4 a —the link  9  is straight and is disposed between the two axes of rotation R and R′. The two complementary stops B 1  and B 2  make it possible to neutralise the torque that tends to cause the side-piece to pivot outwards into an over-opening position. In other words, the normal opening position is a stable position. 
     The stop B 1  on the pivoting head  5 A is inscribed—FIG. 2 a —over a sector with an angle of about 120 degrees, in a diagram cylinder whose axial direction constitutes a second axis of rotation R′ 1  parallel to the first axis of rotation R 1 . The two axes of rotation R 1  and R′ 1  are aligned in a direction L 1  substantially perpendicular to the axial direction A 1  of the hinge element  5  and are spaced apart from one another in such a way that the guide surface S connecting the two female knuckles  5 E is tangent to the stop B 1 . 
     The stop B 2  on the pivoting head  7 A likewise follows—FIG. 3 a —over a sector with an angle γ of about 120 degrees, a diagram cylinder whose axial direction constitutes a second axis of rotation R′ 2  parallel to the first axis of rotation R 2 . The two axes of rotation R 2  and R′ 2  are aligned in a direction L 2  substantially perpendicular to the axial direction A 2  of the hinge element  7  and are spaced apart from one another in such a way that each of the male knuckles  7 E is tangent to the stop B 2 . 
     The stop B 1  is set off towards the outside of the frame in relation to the duct  5 D in the hinge element  5 . In other words, the second axis of rotation R′ 1  is offset towards the outside of the frame in relation to the axial direction A 1 . The stop B 2  is likewise set off towards the outside of the frame in relation to the duct  7 D in the hinge element  7 . In other words, the second axis of rotation R′ 2  is offset towards the outside of the frame in relation to the axial direction A 2 . 
     When the two knuckles are joined together with the aid of the link  9 , the stops B 1  and B 2  come into contact with one another. These stops have the same radius of curvature, so that the second axes of rotation R′ 1  and R′ 2  coincide when the pivoting heads are joined together by the link  9 . The stop B 1  allows the hinge element  7  to pivot, in relation to the hinge element  5 , about the second axis of rotation R′ which designates the axis of rotation R′ 1  or R′ 2 , without distinction. 
     The stops B 1  and B 2  are arranged as a result of complementarity of shape at a pivoting interface so as to allow the side-piece to pivot from the stable normal opening position to an extra outward opening position which is illustrated in FIG. 4 c.    
     In the course of over-opening, the pivoting heads  5 A,  7 A move apart or are uncoupled from one another and the male knuckles  7 E and female knuckles  5 E reduce their contact surface. 
     The link  9  passes successively through the pivoting heads  5 A and  7 A and is supported on the stop B 1  on the outer side of the frame. In this way, it remains offset inwards in relation to the second axis of rotation R′ formed by the interface for the pivoting of the stops B 1  and B 2 . 
     As a result of this arrangement, the tensile force of the link creates a torque for returning the side-piece that tends to oppose the pivoting of the latter in relation to the second axis of rotation R′. This return torque is counterbalanced only when the pivoting heads are inserted in one another again and when the male knuckles are in contact with the guide surface S connecting the two female knuckles, that is to say in the normal opening position. In other words, the over-opening position is unstable. 
     It should advantageously be noted that the spring  15  acts as an over-opening stop when it is compressed as far as possible. 
     The duct  7 D—FIG. 3 a —preferably opens into the pivoting head  7 A via a wind-round surface V 2  which is formed in the intermediate body  7 I and is turned towards the inside of the frame, that is to say has a vector of curvature U 2  which is directed towards the inside of the frame in accordance with the convention defined above. 
     The duct  5 D also preferably opens—FIG. 2 a —into the pivoting head  5 A via a wind-round surface V 1  which is formed in the intermediate body  5 I and is turned towards the inside of the frame, that is to say has a vector of curvature U 1  which is directed towards the inside of the frame. 
     As a result of these arrangements, the link  9  is deformed by following the wind-round surfaces V 1 , V 2  when the side-piece pivots about the axis of rotation R into its closing position. The curvature of the wind-round surfaces V 1  and V 2  is advantageously the same and is, for example, circular in order to accompany the winding-round of the link. 
     According to a variant of embodiment of the invention, the female knuckles  5 E have an internal wall  5 F which is slightly inclined, for example by 15 degrees, in relation to the axial direction A 1 . The male knuckles  7 E can thus be displaced in the direction of inclination of the female knuckles  5 E. This results in a possible swaying movement of the side-piece in relation to the front, in a plane perpendicular to the plane of pivoting. 
     In FIG. 5, a graph shows a comparison between a hinge according to the invention and an ordinary elastic spring hinge using a hinge element which is shaped in the form of a cam and is mobile in rotation about an axis of rotation. 
     Plotted in the form of an arbitrary linear unit on the ordinate of the graph is the modulus of the effort which a user has to apply in order to make the side-piece pivot in relation to the front of the frame. This effort is measured at the same distance from the axis of rotation of the hinge in both cases. The angle of rotation of the side-piece in relation to the front is plotted on the abscissa. The abscissa F corresponds to the closing position of the side-piece, the abscissa O to the normal opening position, and the abscissa T to an extra opening of the side-piece of about 30 degrees in relation to the abscissa O. The curves corresponding to the hinge according to the invention are shown in thick lines, and those corresponding to the hinge for comparison purposes, in thin lines. The continuous lines indicate opening of the frame, and the dotted lines indicate closing. 
     The curve  21  indicating the effort for opening the hinge according to the invention shows that the effort for opening the side-piece is lower than the effort for opening the ordinary hinge. This results in a sense of ease of opening of the side-pieces which favours the hinge of the invention. 
     When the side-piece is closed—curve  22 —the closing effort is very low, which brings a sense of lightness, a simple impact being sufficient to close the frame. By comparison, closure of the ordinary hinge—curve  32 —requires a greater effort. It will also be noted that the angle of compensation, that is to say the angle in respect of which the return torque created by the tensile force is cancelled, is of the order of 60 degrees in the case of a hinge according to the invention, whereas it is 45 degrees in the case of a cam-type hinge. As this angle corresponds to the triggering of automatic closure, the side-piece of the hinge according to the invention does not have to be accompanied for such a long time in order to close the frame. 
     In the extra opening position—curve  23 —the effort rises sharply as a result of the threshold effect so as to reach a plateau. This results in a sense of flexibility in extra opening. By comparison, the extra opening effort of the ordinary hinge—curve  33 —rises sharply then increases in a linear manner with the angle of pivoting, a fact which creates a sense of resistance in constant increase. 
     The fixed element  5  and mobile element  7  of the hinge are advantageously manufactured by a plastic material injection process or a metal powder injection moulding process. 
     The elastic hinge according to the invention permits both a stable closing position and a stable opening position, and an unstable over-opening position. The pivoting heads achieve these three positions without recourse to an articulating screw, a fact which eliminates the risk of unscrewing and of the screw being lost. The link joining the two pivoting heads together is accommodated in the ducts, in such a way that it is invisible from the outside of the frame. The pivoting heads are inserted in one another in the longitudinal direction of the side-piece in a continuous profile and lend an integrated aesthetic quality to the hinge.