Title: "Method of Joining Metal Parts"

Description of Invention

THE PRESENT INVENTION relates to a method of joining metal parts, particularly metal plates or metal parts which are plate-like in the regions to be joined, such parts being hereafter referred to, for convenience, as metal plates.

It is known to join two metal plates by a method commonly referred to as clinching and in which the two metal plates to be joined are placed between a punch member and a die member which are brought together so that, in the region of the punch and die, the material of the superimposed plates is drawn into the die and subsequently deformed or upset in the die to lock the two plates together. It is an object of the present invention to provide an improved method of joining metal parts which is of particular utility where, for example, one of the plates to be joined together is of significantly harder material than the other.

According to one aspect of the invention there is provided a method of joining a first vehicle seat component, comprising a first metal plate and a second vehicle seat component, comprising a second metal plate, comprising forming the first plate with an integral boss projecting from one side thereof, forming the second plate with a hole, fitting the plates together with said boss extending into said hole and deforming or upsetting one or both of said plates in the region of said boss and hole to fix said boss securely in said hole and thus secure the plates together.

In some embodiments of the invention, said boss is pre-formed with a flaring or undercut peripheral wall so that the boss increases in width with distance from the body of the plate with which it is integral and wherein said hole is initially of a size to allow passage of widest part of said boss and wherein, in said forming or upsetting step, the material of said second plate is caused to spread inwardly with respect to the hole, behind the widest part of the boss, to occupy the undercut region around said boss.

In other embodiments, the peripheral wall of said hole increases in diameter or flares so that the hole increases in diameter from the side of the second plate which is to be nearest the first plate and wherein, in said deforming or upsetting step, the material of the boss is caused to spread outwardly to occupy the full width of the hole and prevent subsequent withdrawal of the boss from the hole.

According to another aspect of the invention there is provided a method of joining a first vehicle seat component, comprising a first metal plate and a second vehicle seat component, comprising a second metal plate, where the first metal plate is of a material significantly harder than the material of the second plate, the method comprising forming the first plate with an integral boss projecting from one side thereof, said boss having a flaring or undercut peripheral wall, pressing the first plate against the second plate between opposing dies so as to force said plates together whilst projecting said boss into the material of the second plate, and thereafter causing the material of the second plate to spread into the region behind the widest part of the boss, to occupy the undercut region around said boss.

According to another aspect of the invention there is provided a method of joining a first vehicle seat component, comprising a first metal plate and a second vehicle seat component, comprising a second metal plate, comprising forming said first plate with an integral boss projecting from one

side thereof, supporting said first plate on the other side thereof by a first press member, providing a second press member with a die opening complementary with, and opposing, said boss, locating said second plate between said first plate and said second press member and bringing the first and second press members together so that the boss acts as a punch and co-operates with said die opening to punch a hole in the second plate which hole is occupied by the boss as the first and second plates are brought together, either the boss or the material of the second plate around the boss, or both, being subsequently upset or deformed to secure the first and second plates together.

According to yet another aspect of the invention there is provided a method of joining a first vehicle seat component, comprising a first metal plate and a second vehicle seat component, comprising a second metal plate, where the second metal plate is of a material significantly harder than the material of the first plate, the method comprising forming the second plate with a hole or recess extending from one face thereof, said hole having a flaring or undercut peripheral wall, such that the hole widens away from said one face, pressing the first plate against the second plate between opposing dies of which the die engaging the first plate has a projection engaging the first plate positioned and shaped and dimensioned to correspond with said hole in the second plate, whereby the material of the first plate adjacent the hole is drawn or extruded into said hole to form a projection or boss within said hole and thereafter causing the material of said projection or boss to spread laterally to occupy the widest part of the hole or recess including the undercut or flaring region of said hole.

In carrying out the invention, a plurality of such bosses and holes or recesses receiving the same may be formed in the two metal plates, with the material of one or both of said plates being deformed or upset in the region of said bosses and holes to fix the bosses securely in the holes and thus secure the plates together.

Preferably at least one guiding projection is additionally provided on one of said plates and a respective corresponding complementary hole or recess is provided on the other of said plates such that as the plates are brought together into the relative positions in which they are to be secured together, by the method of the invention, the or each said guiding projection enters the or its complementary hole or recess to ensure correct positioning of the plates with respect to each other.

One envisaged application of the invention is to secure together respective components of a vehicle seat recliner mechanism or of a vehicle seat anti-whiplash mechanism.

The invention also extends to a vehicle seat incorporating components comprising metal plates joined by the method of the invention.

Embodiments of the invention are described below by way of example with reference to the accompanying drawings in which:

Figure 1 and Figure 2 are fragmentary sectional views which show respective portions, to be connected together, of two metal plates,

Figure 3 is a corresponding fragmentary sectional view showing the corresponding parts of the two plates when connected together by a method embodying the invention,

Figure 4 is a fragmentary sectional view illustrating, in the left-hand part of the Figure, a first stage in forming a boss or projection in a plate portion similar to that illustrated in Figure 2, Figure 4, illustrating, on the right-hand side, a second phase in the production of the same boss or projection, Figure 5 is a fragmentary sectional view illustrating the plate portion shown in Figure 4 after the first forming step of Figure 4, and

Figure 6 is a view, similar to that of Figure 4, illustrating the same plate portion after the second forming step of Figure 4,

Figures 7, 8 and 9 are respective sectional views illustrating final forming steps of a joint between two plates according to respective variants of the invention,

Figure 10 is a fragmentary sectional view illustrating, in the left-hand side of the drawing, a first stage in a method, according to a further embodiment of the invention, of connecting two metal parts and showing, in the right-hand side of the drawing, a second stage in the same method, whilst Figure 11 illustrates a further final stage in the same method,

Figure 12 illustrates the two metal parts of Figures 10 and 11 at the beginning of the joining method of Figures 10 and 11 , without the press members or dies shown in Figures 10 and 11 ,

Figure 13 illustrates the final joint resulting from the method of Figures 10 and 11 , again without the press members or dies,

Figures 14, 15 and 16 are fragmentary sectional views illustrating successive stages in a plate joining method according to a yet further variant embodiment of the invention,

Figure 17 is a schematic side elevation view of a vehicle seat with parts which may be assembled by a method in accordance with the invention,

Figure 18 is an exploded perspective view, to a larger scale than Figure 17, showing some of the parts of the vehicle seat of figure 17,

Figure 19 is a side elevation view of part of the seat of Figure 17, showing two of the parts after being secured together by a method in accordance with the invention, and

Figure 20 is a partial view in section on the line XX-XX in Figure 19.

Each of Figures 1 to 14 is a view, in section perpendicular to the planes of the major surfaces of the two metal plates to be joined, or where the parts to be joined are not planar in their entirety, to the planes of the major surfaces of the planar or quasi-planar regions of the two plates at the location where the

joint is to be formed by the method of the invention. As previously noted, in this specification, parts to be joined are referred to for convenience as plates if they are plate-like in the regions where they are superimposed and joined by the method of the invention. In the embodiments of the invention to be described below, the parts to be joined may, for example, be components of a motor vehicle seat.

Referring to Figures 1 to 3, two metal parts 10 and 12 are joined together, in accordance with the invention, by a method which has some similarities, as regards final result, with conventional clinching methods. In the method illustrated in Figures 1 to 3, a first metal plate 10, illustrated in section in Figure 2, is preformed with a projection or boss 14 on one side, for example by a pressing operation, not illustrated, in which a corresponding depression or hollow is formed in the reverse side of the plate 10. The projection or boss 14 is preferably, or at least typically, circular as viewed in a direction perpendicular to the planes of the major surfaces of the plate 10 and the central axis of the boss 14 is shown at A in Figure 2. However, the boss 14 may, if desired, have any shape as viewed along the axis A. Significantly, however, the peripheral wall 18 of the boss 14 flares outwardly in a direction away from the body of the plate 10, i.e. in an upward direction as shown in Figure 2, so that the boss 14 is wider at its termination remote from the body of the plate 10 than it is where it meets the body of the plate and is thus of undercut or dovetail form. The second metal plate 12, as shown in Figure 1 , is formed with a through hole 20, with a peripheral wall 22 which is perpendicular to the planes of the major surfaces of the plate 12 and, as viewed in a direction perpendicular to these planes, is complementary in shape and size with the widest part of boss 14. Thus, where the boss 14 is circular, the wall 22 of hole 20, is a cylinder with axis A, and the hole 20 is of uniform diameter throughout, such that the boss 14 can pass into the hole 20 when the plates 10 and 12 are brought together.

To secure together the two plates shown, the boss 14 is inserted through the hole 20 in the plate 12 of Figure 1 after which the material of the plate 12 is deformed or upset immediately adjacent the hole 20 so that, as shown in Figure 3, the material of the plate spreads inwardly, towards the centre of the hole, to occupy the undercut region around the boss 14. That is to say, in the finally formed joint, the hole has a flaring peripheral shape engaging and entirely complementary with the external periphery of the boss.

In the position shown in Figure 3, this upsetting of the plate 12 has been effected by localised pressure which has produced an annular depression 24 in the surface of the plate 12 remote from the plate 10.

Figure 4 illustrates one way of forming the boss 14 in plate 10 of Figure 2. Thus, in a first operation, a plate blank is pressed between a first press member having a projection 32 and a second press member 34 with a die 36 in which is formed a die opening with a peripheral wall which increases in diameter somewhat with distance away from the surface of the die 36 which directly opposes the first press member 30, that is to say the die cavity is undercut somewhat. In a first phase of the pressing operation, as illustrated in the left-hand side of Figure 4, as the press member 30 is forced towards the press member 34, the material of the plate 10 under the projection 32 is caused to flow into the die cavity - is effectively extruded into the die cavity - to form a boss 14 within the die cavity which boss has at least initially a generally cylindrical outer surface which is in contact with the peripheral wall of the die opening at the upper outer end of the die opening but is spaced radially inward from that peripheral surface at the bottom of the die. A counter punch 38 extending within the die 36 is then forced upwardly, as illustrated in the right hand side of Figure 4, to engage the end of the boss within the die, thereby deforming the boss to expand the latter at its free (lower) end, so that the boss assumes the desired tapering or flaring form. Alternatively, of course, the die 36 may be solid with a bottom surface of the die cavity corresponding

to the upper surface of the counter punch in Figure 4, so that after the free end of the boss meets the bottom of the die cavity, further movement of the press member 30 towards the press member 34 forces the material of the boss to spread outwardly into the undercut portion of the die cavity.

Where the method of the invention is conducted in accordance with Figures 1 to 3, the material of plate 10 is preferably significantly harder than that of plate 12 at the time the plates 10 and 12 are joined together. However, the operation described with reference to Figure 4 may be carried out when the material of the plate 10 is relatively soft, e.g. before a hardening process is supplied to the plates or in a hot forging operation, with the plate being hardened after the boss 14 has been fully formed.

The die 36 is, of course, split longitudinally, e.g. along the vertical line A in Figure 4, to allow subsequent extraction of the boss 14 from the die cavity.

The deformation of the material of the second plate 12 around the hole 20, once the boss 14 has been projected through the hole 20 and the plates 10,12 brought together, as illustrated in Figure 3, may be effected in various ways. Thus, the two plates may simply be brought together between opposing press members one of which is formed with an annular ridge or the like which engages the border region of the second plate around the hole 20 and deforms the material of the second plate to cause it to flow into the undercut region around the boss 14. Alternatively, a die 40 which is rolled around the annular region around the periphery of the hole 20, as illustrated in Figures 7, 8 and 9 may be used to effect such deformation. In the method illustrated in each of these Figures, the die 40 used has a rotational symmetry about an axis B which is inclined at an angle relative to the normal to central axis A of the hole 20 and the boss 14, (the axis A being normal to the planes of the plate-like elements being joined), the movement of the die 40 being such that the axis B is rotated around the axis A as the die 40 rolls around the edge

region of the hole 20. In the arrangement illustrated in Figure 7, the operative face of the die 40 provides an annular rib which forms a corresponding indentation in the co-operating surface of the upper plate 12 whilst at the same time causing the material of the upper plate to flow into the undercut region defined around the boss 14 in the lower plate. In the arrangement of Figure 8, the upper plate 12 is pre-formed with a raised annular area 42 around the hole 20 which receives the boss 14 of the lower plate, and the die 40, by flattening or partially flattening this raised area 42, forces the material of the upper plate 12 into the undercut region around the boss 14. In the arrangement of Figure 9, the die 40 operates in substantially the same way as in the arrangement of Figure 7, but the embodiment illustrated in Figure 9 differs from that of Figure 7 in that the upper plate 12 is not pre-formed with a hole to receive the boss 14 in the lower plate 10, but merely has a recess in its underside which receives that boss and which may, typically, be formed by a pressing operation between appropriately shaped press members engaging the upper plate 12 and the lower plate 10 and which leaves only the upsetting of the upper plate 12, to cause the material thereof to flow into the undercut region around the boss 14, to be effected by the die 40.

Figures 10 to 13 illustrate a variant method in which the plate 12 formed with the hole 20 is preformed in such a way that the peripheral wall 43 of the hole is flared or expands in width with distance away from the plate 10 to which the plate 12 is to be attached and in which the plate 10 is deformed to provide a boss 14 which is extended through that hole 20 and is subsequently upset to occupy the undercut region of the hole. Thus, in Figure 10, there is shown, to the left-hand side of the centre line A, (which, as in the other embodiments, is perpendicular to the planes of plates 10,12), an initial position in which the lower plate 12 with a preformed hole 20 is supported on a press member 44 which has a through passage 46 aligned with the hole 20 and within which passage 46 is vertically moveable a punch member 48. In this variant, the plate 12 with the hole 20 is of significantly harder material than the

plate 10, and may, for example, have been subjected to a hardening operation after forming the hole 20 and, of course, before plate 12 is placed on the press member 44.

The plate 10 to be secured to the plate 12 is illustrated as being initially flat and planar in the region of the intended attachment to the plate 12 (as also shown in Figure 12), and is engaged on its upper surface by a press member 52 within which is mounted, for vertical movement in a vertical passage in the member 52, a punch member 54 with a cross-sectional shape corresponding to that of the hole 20 and the passage 46, but somewhat larger in diameter than the hole 20 and passage 46. In a first step, the end of which is illustrated on the right-hand side of the broken line A in Figure 10, the punch member 54 is forced downwardly against the plate 10 causing the region of plate 10 over the hole 20 to be, in effect, extruded through the hole 20 until the lower surface of the extruded portion is substantially in the same plane as the lower surface of the plate 20. The extruded portion thus forms the desired projection or boss 14 within the hole 20. However, at this stage the peripheral wall of this boss 14 is substantially perpendicular to the major planes of the plates 10,12 so that the opposing peripheral surface 43 the hole 20 is spaced progressively further from the opposing peripheral surface of the boss 14 with increasing distance away from the major planes of the plate 10 and towards the underside of the plate 12. In the next phase, illustrated in Figure 11 , the punch 48 is forced upwardly against the underside of the boss portion 14 of the plate 10 within the hole 20, expanding the lower region of the boss portion 14 radially outwardly to occupy the undercut region of the hole 20 and thus ensure a firm connection between plates 10 and 12, as illustrated in Figure 13.

In a further variant, not shown, the plate 12 may be formed with an undercut recess in its upper surface, instead of a through hole and the boss 14 may, after being drawn or extruded into this recess, be caused to spread

laterally to fill the undercut simply by continued pressure resulting from continued advancement of the press members 52,44 towards one another.

In a further variant illustrated in Figures 14 to 16, the upper plate 10 is preformed with a boss 14 having an undercut or flaring peripheral surface and which boss 14 is effectively used as a punch to punch a complementary hole in the lower plate 12. In this case, of course, the material of the upper plate 10 is made significantly harder than that of the lower plate 12. In this embodiment, the superimposed plates 10, 12 to be joined are again located between opposing press members, referenced 52 and 44 in Figures 14 to 16.

The upper plate 10 is located on the underside of upper press member 52 which has locating formations, (shown as projections 53, 55), which engage complementary locating formations (shown as recesses), on the upper side of the plate 10. Likewise, the lower plate 12 is suitably located on the lower press member 44, for example by locating pins, one of which is illustrated at 60, engaging in complementary holes in plate 12. In the arrangement illustrated, the upper plate 10 is additionally provided with a locating projection or stub 62 aligned with the pin 60 and the hole in plate 12 which receives pin 60. The press member 44 is provided with a die opening 46 complementary in size and shape with and directly opposing the boss 14 of plate 10 and accordingly, when the press members 44 and 52 are brought together as illustrated in Figure 15, the boss 14 punches from the plate 12 a piece 64, which exits through the die opening 46 in press member 44 and at the same time the boss occupies the resulting hole in the plate 12. At the same time the locating projection 62 on the plate 10 enters the locating hole in the plate 12, the pin 60 moving down in the press member 44 to make way for projection 62. It will be noted that, in the position shown in Figure 15, the peripheral wall of the hole punched in the plate 12 is again substantially perpendicular to the major faces of the plate 12 and thus does not yet occupy the undercut region around the boss 14. However, it will also be noted that there is provided, around the upper end of the die opening in the press member 44, projecting

upwardly from the upper surface of the press member 44, an annular ridge or collar which up to this point, (as shown in Figures 14 and 15), has effectively supported the plate 12 by engagement with the underside thereof, the neighbouring regions of the plate 12 having their undersurface thus spaced from the remainder of the upper surface of the press member 44. However, during the final movement of the press members 44 and 52 together, into the position illustrated in Figure 16, the annular collar around the die opening is forced into the underside of the plate 12 upsetting the material of the plate 12 to cause this material to flow into the undercut region around the periphery of the boss 14, again to secure a firm joint.

The locating projection or stub 62 may be tapered conically slightly, at least adjacent its free end, to ensure its ready entry into the opposing hole in plate 12. It will be understood that, typically, the plate 10 may have a plurality of locating projections or stubs 62 and the plate 12 may have corresponding holes to receive the same, to ensure that the plates to be joined are correctly located with respect to each other. Such locating projections and complementary holes to receive the same may be provided on the plates to be joined in the arrangements described with reference to Figures 1 to 13 also, of course. The locating projections need not be on the same plate as the boss 14 or the complementary holes in the same plate as the plates with the hole which receives the boss. Of course any of various other ways of locating the plates 10, 12 to be joined prior to and during the pressing and upsetting or riveting operations may be used.

By way of illustration of the sort of application for which the method according to the invention may be useful, there is illustrated in Figure 17 part of a motor vehicle seat incorporating a recliner mechanism allowing the seat back to be tilted backwards or forwards with respect to the seat base. The seat arrangement illustrated may also incorporate an anti-whiplash mechanism (not shown in detail). The seat arrangement shown comprises a first metal

bracket 70 secured to, or forming part of the seat back frame, a further metal bracket 72 secured to or forming part of the seat base frame and a pivot and adjustment mechanism indicated at 74. The precise nature of the pivot and adjustment mechanism 74 is not described here but it should be noted that this comprises generally flat parallel plate members 76, 78, (see Figure 18), which are pivotable with respect to each other under the constraint of the adjustment mechanism, which typically may comprise a gearing arrangement operable by a manual knob or by an electric motor (not shown). The plates 70, 72 are also generally parallel with each other. The method of the present invention may be used, for example, to secure the plate 76 to the plate 70 as shown in section in Figure 20. In the arrangement illustrated, the plate 76 is provided with locating projections 79 to locate in complementary holes 80 in the plate 70 and is provided with flaring or dovetail section holes 82 to receive bosses 84 provided on the plate 70 and which bosses 84 after insertion in the holes 82 are upset or riveted, for example as described with reference to Figures 10 to 13, with the material of the plate 70 being pressed or extruded through the holes 82 to form the bosses 84 and the bosses 84 being upset or riveted in the holes 82 or, for example, with the bosses 84 being preformed, with cylindrical, uniform diameter, peripheral surfaces, before insertion in the holes 82 and being subsequently upset or riveted in the holes 82. Alternatively, of course, the plates 70, 72 may be secured together by the particular variants of the method of the invention which are described with reference to Figures 1 to 3 or with references to Figures 4 to 9 or with reference to Figures 14 to 16. In the same manner as described above, the plate 78 may be secured to the plate 72 by a method embodying the invention. Depending on the structure of the seat frame and the point in the manufacturing process at which the operation is carried out, the plates 70, 76 may be secured together before or after the plates 70 and 72 are secured to the seat back frame or the seat base frame respectively.

It will be understood that where the seat incorporates an ant-whiplash mechanism, which may, for example swing a headrest of the seat forwards relative to the seat back in the event of a rear impact to the vehicle in which the seat is fitted, the head rest may be mounted on the seat back by way of a mechanism which, like the seat back adjusting mechanism illustrated in Figures 17 to 20, incorporates plates secured to corresponding plates on, or plate-like parts of, the seat back and of the head rest, by any of the variants of the method of the invention described above.