[ 0026 ] fig1 shows a lounge chair articulation mechanism 1 in a perspective view in its position of use . this lounge chair articulation mechanism 1 comprises a center part 2 , a head part 3 as well as a leg part 4 ; in this connection , the term leg part refers to the support leg of a lounge chair . the center part 2 is comprised of two shaped elements 5 , 5 ′; in the illustrated embodiment , they are shaped sheet metal pieces . these shaped sheet metal pieces 5 , 5 ′ comprise inner shells 7 , 7 ′ and form a socket 5 * by means of an elongate area . the head part 3 is comprised of two shaped elements 6 , 6 ′, also embodied as shaped sheet metal pieces comprising each an outer shell 8 wherein the elongate sections of the shaped sheet metal parts 6 , 6 ′ form a socket 6 *. the outer shell 8 is provided with several impressions which form inwardly oriented projections 9 ; they will be discussed in more detail in connection with the other figures . the inner shells 7 , 7 ′ and the outer shell 8 are arranged concentrically to one another . a rivet 11 extends through a central bore in each one of these shells ; the rivet 11 forms the axis of rotation or pivot axis for the center part 2 and the head part 3 forming the articulation . the leg part 4 comprises wall parts at its upper end ; fig1 only shows one wall part 13 connected by means of a rivet 12 like a hinge to the center part 2 formed of the shaped sheet metal parts 5 , 5 ′. in order to ensure locking of the leg part 4 in the position of use , the outer shell 8 is provided with an outwardly projecting embossment 14 having essentially the shape of a circle sector wherein the arc surface of the embossment 14 cooperates with a glide contour 15 provided on the wall part 13 having a curvature matched to the radius of the circle sector . it can be seen that the leg part 4 can be pivoted toward the center part 2 only when the head part 3 is folded inwardly and , in this way , the embossment 14 is positioned outside of the pivot area of the wall part 13 . [ 0028 ] fig2 shows an exploded view of the articulation mechanism 1 . this figure shows that the shaped sheet metal parts 5 , 5 ′ form therebetween a hollow space into which a slide 25 and a spring 23 are inserted . the spring 23 is positioned in a socket 5 * formed by the shaped sheet metal parts 5 , 5 ′ and is supported with the outer end on a spring stop 24 that is a monolithic part of the shaped sheet metal parts 5 , 5 ′. the inner shells 7 , 7 ′ are provided with slot - shaped openings 30 , 30 ′, 31 , 31 ′ through which teeth project that are provided on the slide 25 and act as looking members 26 , 28 . the slide 25 has a bent section 27 having at its forward end the looking members 26 provided with a straight leading edge 35 . the spring 23 is acting on a section 34 of the slide 25 , and in the vicinity of this section two lateral teeth are provided which act as looking members 28 . the slide 25 is inserted with the looking members 26 into the openings 30 , 30 ′ and with the looking members 28 into the openings 31 , 31 ′. on the inner shell 7 , the opening 31 has a section 31 ″ on which a step 31 * is formed behind which the locking members 28 can be hooked . it may be advantageous to provide in addition to this hooking function on a lateral edge of the slide 25 an additional tooth 29 . this tooth engages a guide slot 32 of the inner shell 7 ′ and reaches in a certain position of the slide a section 32 ′ of the guide slot 32 behind a step 32 * so that the slide 25 can no longer be moved . the two inner shells 7 , 7 ′ have depressions 18 which are circular and are positioned at a certain spacing relative to the rims 17 , 17 ′. the spaced arrangement creates an annular surface 19 . the two shaped sheet metal parts 5 , 5 ′ rest against one another by means of the open edges of the rims 17 , 17 ′ and form a closed hollow space between the inner shells 7 , 7 ′. in the depressions 18 of the inner shells 7 , 7 ′, the outer shells 8 , 8 ′ of the shaped sheet metal parts 6 , 6 ′ are arranged . they have inwardly oriented projections 9 , 10 , 38 , 39 cooperating with the locking members 26 and 28 . the engagement of the locking members 26 , 28 in the intermediate spaces between the projections 9 and 10 can be seen in particular in fig5 . as is also illustrated in fig2 a first group of projections comprises several projections 9 as well as a projection 38 and a projection 46 ; a second group of projections positioned diametrically opposite to the first group comprises projections 10 and includes a projection 39 . the shape of the projections of the respective group is selected such that between them intermediate spaces result which form identical locking surfaces and glide surfaces — with the exception of projection 38 . the function of the projections 38 and 39 will be explained in more detail in connection with fig6 and 7 . the outer shells 8 , 8 ′ have at their periphery a circumferentially extending flange 33 which covers the annular surface 19 of the inner shells 7 , 7 ′ and in this way prevents the penetration of dirt into the recess 18 . as can be seen in fig2 the outer shells have central bores 20 , 20 ′ and the inner shells 7 , 7 ′ have central bores 21 , 21 ′ through which the rivet 11 extends that provides a pivot axis for the shaped sheet metal parts of the center part and of the head part pivotable relative to one another . bores 22 , 22 ′ are provided on the shaped sheet metal parts 5 , 5 ′ which are congruent to one another . the leg part 4 has at its upper end the already mentioned wall part 13 and a parallel extending wall part 13 ′, wherein the two wall parts 13 , 13 ′ are provided with congruent bores 16 , 16 ′. the leg part 4 engages with its wall parts 13 , 13 ′ the center part 2 and the rivet 12 extends through the bores 16 , 16 ′, 22 , 22 ′ so that the axis of rotation ( pivot axis ) for the hinge - like articulation mechanism between the center part 2 and the leg part 4 is formed . the configuration of the embossment 14 and of the gliding contour 15 has been described already in connection with fig1 . in addition , fig2 also shows that a projecting member 45 is formed as a monolithic part of the outer shell 8 ′ and extends radially and axially outwardly . its function will be explained in the following in connection with fig3 . on the leg part 4 support edges 44 are formed ; they rest in the position of use of the lounge chair articulation mechanism against the outer circumference of the shaped sheet metal parts 5 , 5 ′. [ 0033 ] fig3 shows a side view of the lounge chair articulation mechanism 1 in the folded state . the sockets 5 * and 6 * are parallel to one another , i . e ., the head part 3 is pivoted onto the center part 2 . the leg part 4 is also pivoted onto the center part 2 and extends also essentially parallel to the center part 2 . the projecting member 45 formed on the outer shell 8 ′ is positioned against a locking edge 41 of the wall part 13 ′ so that it is prevented that the head part 3 can be folded out as long as the leg part 4 has not yet been pivoted by a predetermined angle about the rivet 12 . in this way , a sequence for manipulating the lounge chair is ensured , i . e ., the leg part 4 must be pivoted first before pivoting of the head part 3 is enabled . the configuration of the wall part 13 ′ illustrated in fig3 has a transitional portion 42 adjoining a driver section 43 so that the leg part 4 must be moved at least with its transitional portion 42 past the projecting member 45 in order to enable movement of the head part 3 relative to the center part 2 . if the leg part 4 has not been completely folded out , the movement of the head part 3 relative to the center part 2 generates the residual pivoting action of the leg part 4 by means of force introduction of the projecting member 45 onto the driver section 43 . for identical parts , the reference numerals in fig3 match those of fig1 and 2 . [ 0034 ] fig4 shows a side view of the lounge chair articulation mechanism 1 with completely folded - open leg part 4 but with the head part 3 still in the folded position . in addition to the illustration of fig3 fig4 shows in dashed lines the position of the slide 25 and of the spring 23 acting on it . [ 0035 ] fig5 shows a section along the line v - v of fig4 . this illustration shows that the rims 17 , 17 ′ of the inner shells 7 , 7 ′ rest against one another and in this way form a hollow space within the inner shells which is closed off to the exterior . on the outer sides the inner shells 7 , 7 ′ are covered by the outer shells 8 , 8 ′ wherein the flange 33 rests against the annular surface 19 and in this way prevents the penetration of dirt . the slide 25 is in the end position into which it is moved against the force of the spring 23 so that the looking members 26 and 28 are moved out of the intermediate spaces between the projections 9 and 10 . fig5 also shows that the looking members 26 and 28 project so far into the hollow space formed by the outer shells 8 , 8 ′ that upon engagement between the projections 9 and 10 a locking action against pivoting of the head part 3 relative to the center part 2 is achieved . [ 0036 ] fig6 through 8 show the inner side of the center part 2 and the head part 3 in different operational positions of the articulation mechanism . since in the folded state according to fig4 the slide 25 is in the position in which it is moved against the spring 23 and secured in this position in an immobile way , upon folding open the articulation mechanism , i . e ., pivoting the head part 3 relative to the center part 2 — in the example of fig6 in the clockwise direction — no locking action is effected because the projections 9 and 10 are outside of the movement path of the looking members 26 , 28 . when the head part 3 reaches the position illustrated in fig7 the projection 39 comes to rest against the slide 25 , in particular on the additional tooth 29 , and in this way moves the slide 25 , i . e ., its teeth 28 and 29 , out of engagement behind the projections 31 *, 32 * into a position in which the locking members and the additional tooth are no longer secured ; the slide 25 is now movable longitudinally . when the head part 3 is pivoted from this position in a counterclockwise direction , as illustrated in fig8 the leading edge 35 of the slide 25 glides along the slanted surfaces 36 on the projections 9 and the slide 25 is moved against the spring 23 to such an extent that the locking members 26 and 28 are moved past the projections 9 and 10 , respectively , and then lock behind them as a result of the action of the spring 23 . accordingly , in the desired position the locking surface 37 of the projection 9 rests against the locking member 26 and the diametrically oppositely positioned projection 10 rests against the locking member 28 . when a more upright position of the head part 3 is desired , a movement is possible in a counterclockwise direction , as described above . for lowering the head part 3 , the slide 25 must be moved into a position in which the locking members 26 , 28 cannot engage the projections 9 and 10 . for this purpose , a long side 40 is provided on the projection 38 by which the slide 25 can be moved against the spring 23 until the locking member 28 or the additional tooth 29 reaches the sections 31 ″ and 32 ′ of the guide slots so that the area 34 of the slide 25 is pushed by the spring into a position behind the projections 31 *, 32 *. in this way , the slide is no longer movable in the longitudinal direction in this position . [ 0040 ] fig9 shows an alternative configuration of the center part 2 and of the head part 3 where the inner shells 7 are components of the head part and the outer shells 8 components of the center part . this configuration requires that the spring 23 is arranged in the socket 6 * of the head part . otherwise , the arrangement is identical . while specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles , it will be understood that the invention may be embodied otherwise without departing from such principles .
an articulation mechanism has a central part and a head part each made of a pair of shaped elements . the pairs of shaped elements form inner and outer shells . the inner shells are positioned inside the outer shells . the pairs of shaped elements are pivotable relative to one another and lockable relative to one another in several positions in one pivot direction . the outer shells have inwardly oriented projections and the inner shells have openings . a slide is moveably arranged inside the inner shells . the slide has locking members projecting through the openings of the inner shells and engaging intermediate spaces of the projections . a spring acts on the slide in an engagement direction of the locking members relative to the projections . the projections are shaped such that the locking members automatically reach a locking position in a first pivot direction of the head part .