Note: Descriptions are shown in the official language in which they were submitted.
CA 02235636 1998-04-23
1
1 Title: SECUREMENT OF HEAD REST SUPPORT INTO AUTOMOBILE SEAT FRAME
z
3
4 This invention relates to the construction of automobile seats,
s and is directed particularly to the manner of attachment of a
s headrest to the frame of an automobile seat.
a
9 BACKGROUND TO THE INVENTION
to
11 The headrest on an automobile seat is often made adjustable as to
1z height. One common way in which the headrest is mounted on the
13 seat in a way that permits height adjustment is for the headrest
14 to be provided with two downwardly extending pegs, and the pegs
is engage sockets secured into the frame of the seat. Detent means
is are usually provided which interact between the pegs and the
l sockets, whereby the headrest may be set, by the occupant of the
1e vehicle, at one of a number of pre-set heights.
19
zo The socket in which the peg is received comprises a metal tube.
z1 A plastic liner may be provided in the tube, to act as a bearing
zz material for the peg. In the conventional system, the tube is
z3 welded to a bracket, and the bracket is welded to a frame piece
z4 of the seat. This manner of attachment, though secure enough
25 (because it has to be secure by regulation}, unfortunately is
zs expensive as to the labour time and the materials needed to make
z~ it that secure. Any securement system that involves welding
2e tends to be labour-intensive and therefore expensive, besides
z9 being difficult to inspect and test. A welded system generally
3o has to be over-engineered.
31
3z Also, welding does not lead to high accuracy. The need for
33 accuracy of placement of the headrest on the seat is not high,
34 although the accuracy of the spacing of the pegs and their
3s sockets cannot be too far out; the conventional welded-on system
3s is just about at the limit for accuracy for welding, which means
3~ that, when welding is used as the basis of the attachment method,
3a skilled care has to be taken, which in turn does nothing to ease
39 the cost problem.
41 The invention is aimed at providing a manner of securing a
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z
1 headrest support tube into a seat frame, in a manner that eases
z some of the compromises that have had to be resorted to in the
3 conventional systems.
4
s Typically, the operations carried out in a conventional seat
s manufactory include welding, bending of frame pieces, securing
components together, and assembly, all of which tend to have a
a higher labour content. It is an aim of the headrest support
s system as described herein, to minimise the labour content of the
to task of attaching the support tubes to the seat frame piece.
11
12 Support tubes for headrests are conventionally attached to the
13 seat frame piece by welding a bracket onto the frame piece, and
14 then welding the tube to the bracket. Sometimes, the tube is
is pressed into holes in the welded-on bracket; but welding is
is nearly always resorted to, to assure that the tube remains in
l position on the bracket. Of course, the tubes can be attached
1e securely enough, but the conventional costs of ensuring that
is security are high.
21
z2 GENERAL FEATURES OF THE INVENTION
23
z4 The invention lies in the manner of attaching the headrest-
z5 support-tube. First, the headrest-support-tube is provided with
zs a first ring, in which the metal of the headrest-support-tube is
z~ expanded radially outwards. The headrest-support-tube is
2e assembled into a hole in the web of the seat-frame-piece, with
is the first ring abutting against the web.
31 The frame-piece, with the headrest-support-tube resting therein,
3z is placed in the die of a punch and die set, with the first ring
33 in the die. The punch then is brought down over the other end of
34 the headrest-support-tube, and a second ring is formed on the
other side of the web. When the punch is withdrawn, the web lies
3s gripped between the two rings. Usually, another headrest-
3~ support-tube is inserted into the frame-piece, in a similar
3e manner. Then, the seat-frame piece is assembled into a seat, and
39 finally the pegs of the headrest are inserted into the headrest-
4o support-tubes.
41
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1 THE PRIOR ART
2
3 As mentioned, headrest-support tubes are attached to the seat-
a frame-piece by welding. Sometimes, designers have specified
s intermediate brackets, rather than just welding the tube to the
s frame piece.
s Techniques for mounting a tube into a through-hole in a piece of
9 sheet metal are commonplace, per se. The broad range of options
to available include bulk-head fittings generally. Such fittings
11 have included cases where a first bead is provided on the tube on
12 one side of the sheet, then a second bead is swaged into the tube
13 after the tube has been inserted into the through-hole. The
14 technique is commonly known as lock-beading.
is In cases where bulk-head fittings are being designed, a common
1~ requirement is that the fitting by air- or liquid-tight. It is
1e recognised that the lock-beading technique is not suitable for
19 such cases. It is recognised that lock-beading is highly
zo suitable for cases where mechanical integrity is paramount,
z1 rather than sealing. It is also recognised that lock-beading is
z2 highly suitable for cases where access to the beads is only to be
z3 had from an axial direction, such as a case where flat-access to
24 the through-hole is denied because the through-hole is surrounded
2s by raised flanges.
2s
z~
2s DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
29
3o By way of further explanation of the invention, exemplary
31 embodiments of the invention will now be described with reference
32 to the accompanying drawings, in which:
33
34 Fig 1 is a diagram of an automobile seat frame, shown partly in
3s cross-section, carrying a headrest which is mounted in a
3s manner in accordance with the invention;
3~ Fig 2 is a view of some of the components that support the
38 headrest, shown at a preliminary stage of manufacture;
39 Fig 3 is a view of a punch and die set-up, which is used at a
4o stage in the manufacture of one of the headrest supports;
41 Fig 4 is a view corresponding to Fig 3 of another stage during
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1 manufacture;
z Fig 5 is a cross-section of the headrest mounting support, shown
3 at a later stage;
4 Figs 6a,6b,6c are cross-sections of a tooling arrangement for
s forming a metal tube locally into an I-section beam;
s Figs 7a,7c are views on the line 7-7 of Fig 6a, corresponding to
the conditions shown in Figs 6a and 6c respectively;
s Figs 8a,8b are cross-sections of a hole-punching arrangement, for
9 making a through-hole in the web of the I-beam produced as
to in Fig 6c;
11 Fig 9 is a view of a headrest-support-tube, shown prior to final
12 forming;
13 Figs lOa,lOb,lOc are cross-sections of a tooling arrangement for
14 ring-bead-locking the headrest-support-tube of Fig 9 into
is the through-hole in the web of the I-beam.
16
l The apparatuses shown in the accompanying drawings and described
is below are examples which embody the invention. It should be
19 noted that the scope of the invention is defined by the
zo accompanying claims, and not necessarily by specific features of
21 exemplary embodiments.
22
23 Fig 1 shows an automobile seat 20, having a seat frame piece 23.
z4 In this case, the seat frame piece 23 made from a length of
z5 extruded I-section aluminum. The seat frame piece is bent
2s generally into an inverted U-shape, as shown, in which the
2~ horizontal rail 24 of the U-shape forms the horizontal top rail
2a of the seat.
29
so The headrest 25 of the seat 20 is formed with two pegs 26, which
s1 protrude downwards, as shown. The pegs engage into support tubes
3z 27, which are integral with the frame of the seat. The support
33 tubes 27 are fixed firmly to the horizontal rail 24, and in fact
34 the support tubes pass through holes 28 in the web 29 of the I-
3s section that forms the rail 24 (see Fig 2).
36
3~ The invention is concerned with the manner of attaching the
ss support tubes 27 into the holes 28 in the web 29 of the
39 I-section. Usually, headrests are adjustable as to vertical
4o position, and the adjustment is effected by moving the headrest,
41 with its two pegs 26, vertically up or down within the tubes 27.
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1 The designer can provide a plastic sleeve 30, which is inserted
z into the support tube to provide a bearing for guiding the pegs
s for up/down adjustment movement. The designer can provide the
4 pegs with detents (not shown), which interact with the plastic
5 sleeves 30, or with the tubes 27, in order to define some
s vertical positions to which the headrest might be set. It is
usually necessary to align the plastic sleeve orientationally
a with respect to the tube, and the plastic sleeve can be moulded
s with a tongue for engagement with a notch 32 (Fig 5) in the tube,
to for this purpose.
11
12 In order to manufacture the seat frame, with the headrest support
13 tubes 27 attached, first the tubes are formed with a single first
14 swaged-out ring 34. The tube in this state is as shown in Fig 2.
16 The swaged-out ring 34 is formed by pressing the ends of a plain
1~ length of tubing axially, and confining the walls thereof
la everywhere but at the place where the ring is to be formed. It
1g may be noted that this first operation is carried out on the tube
2o when only the tube itself is present, i.e in the absence of any
21 other components. The operation of forming the first ring is of
zz low labour content, and can be easily automated.
23
24 The job of attaching the tube 27, with its first swaged-out ring
34, into the hole 28 in the web 29 of the I-section, can also be
2s fully automated, as can the job of swaging the first ring into
2z the tube. This may be compared with the job of welding a bracket
2e onto the frame piece, and then locating a tube into holes in the
2s bracket, and then welding the tube to the bracket, in which the
labour content is inevitably high.
31
3z Fig 3 shows the tube 27, with its first swaged-out ring 34,
33 resting in a die 35. The seat frame piece 23 has been placed
3a over the tube 27, with the web 29 resting against the first ring
34. A punch 36 is advanced, and a hole 37 in the punch slides
3s over the upper portion of the tube 27. When the end of the hole
3~ 38 bottoms against the end 39 of the tube 27, further movement of
3a the punch causes the upper portion of the tube to be compressed.
39 A recess 40 in the punch allows the metal of the tube to expand
outwards, in response to the axial force, with the result that
41 the action of the punch causes a second ring 42 to be formed in
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1 the tube.
2
3 Fig 4 shows the situation when the punch and die are (almost)
4 closed fully together. It will be seen from Fig 4 that the web
s 29 is not contacted by either the die 35 or the punch 36 during
s the operation of swaging out the second ring 42. At the very end
of the operation, the designer might provide that the web is in
a fact subjected to a squeeze between the punch and die, as a
9 coining phase to ensure everything is straight; but in general,
to throughout the pressing stages indicated in Figs 3 and 4, the web
ii 29 floats. As the pressing operation is nearing completion, the
12 press forces also act on the first ring 34, and cause that to be
13 consolidated and even coined.
14
is The hole 28 in the frame piece is a clearance fit over the
is diameter of the tube 27, and so the frame-piece is not held in
1~ position, during the Fig 4 operation, by being held by a tight
la fit on the tube 27. Therefore, the frame-piece 23 does need to
19 be held -- at least loosely -- to prevent tipping thereof.
zo However, that kind of holding is simple enough -- at least when
21 compared with securing the components in welding jigs.
22
z3 It is important, during the Fig 4 pressing operation, that the
z4 web 29 remain resting in close touching contact with the first
zs ring 34. In an automated system, the designer should ensure that
zs the components are presented properly to each other for the
z~ operation. Seat-frame-pieces can include bends and twists, and
ae be of an awkward shape, but the designer can provide the holding-
z9 clamps etc to accommodate whatever shape the seat-frame-pieces
3o are in. The designer can decide whether to insert the head-rest-
31 support-tubes into the seat-frame-piece before or after the seat-
3z frame-piece is bent and twisted to its final shape.
33
34 The designer should ensure that, whatever the configuration of
35 the components, the web can and does rest properly (i.e in firm
3s abutment) against the first ring during the operation of pressing
3~ the second ring: if there were to be some clearance between the
3a web and the first ring during pressing, the final joint would be
39 significantly less tight and secure. The ideal is that the web
4o should be under some degree of residual compression after the
41 punch and die have separated, even if only slightly, and that can
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1 only happen if the web remains cleanly in abutment against the
z first ring throughout the pressing operation.
3
4 In an alternative, the die and punch set may be arranged with a
subsidiary actuable member, which loads the web tightly against
s the first ring while the forming of the second ring is taking
place.
a
g It is important also that the clearance between the hole 28 in
to the web and the diameter of the tube 27 be taken up during the
11 pressing operation. The force that causes the metal of the tube
1z to swell out to form the second ring 42, of course also causes
13 the metal to swell out to fill the clearance at the hole 28.
14 Generally, the filling of the hole 28 is so good that any
crannies etc caused by burrs or other malformations arising from
is the punching of the hole 28, are filled completely and tightly.
17
is The manner as described above of attaching the headrest support
19 tubes to the seat frame provides a very secure attachment, which
is amply able to accommodate the forces and abusive forces
z1 encountered in automotive seating equipment. The material costs
z2 are somewhat reduced, and the labour costs are very much reduced,
23 as compared with what has to be done in the conventional tasks of
z4 welding the tubes to the frames.
zs It is conventional for the frames of automobile seats to be made
2~ from steel tubing. The head-rest-support-posts can be attached
2a into a tubular-steel seat-frame in the manner as will now be
z9 described.
31 Figs 6a,6b,6c are views directed axially along the length of the
3z seat-frame-tube 50, and show three stages in the preparation of
33 the seat-frame-tube. Figs 7a,7c are views corresponding to Figs
34 6a,6c in the direction of arrows 7-7 of Fig 6a.
3s In Fig 6a, the seat-frame-tube 50 has been gripped on its outside
diameter between two dies 52x,52y. The dies are dimensioned to
3e grip the seat-frame-tube at two spaced locations 53,54. The dies
39 52x,52y are shaped so as not to directly grip the seat-frame-tube
50 in the recess 55 between the locations 53,54.
41
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a
i Once the dies 52x,52y are in contact, and the seat-frame-tube 50
2 is firmly held, the two formers 56x,56y are advanced. At first,
3 the seat-frame-tube 50 is flattened, as shown in Fig 6b. As the
4 upper and lower zones 57x,57y of the tube walls are forced
s together, the left and right side-zones 58L,58R are forced apart,
6 and these zones of the walls come into contact with the sides
59L,59R of the recess 55.
a
s The formers 56x,56y are advanced until they bottom against the
io two thicknesses of the wall-zones 57x,57y, as shown in Figs
ii 6c,7c. The wall-zones 58L,58R are formed to the shape as shown
i2 by virtue of their confinement by the sides 59L,59R of the recess
is 55. It will be noted that this manner of forming the seat-frame-
i4 tube produces a localised shape which is similar to that of an I-
15 beam. The web 60 of the I-beam shape is derived from the wall-
i6 zones 57x,57y, and the flanges 62L,62R of the I-beam are derived
m from the folded wall-zones 58L,58R.
ie
i9 It is noted that the seat-frame-tube 50 is not simply squashed
Zo flat. The operations as described produce a configuration that
zi is much stronger and more rigid than a flattened tube. The
zz flanges 62L,62R, being tall (i.e the height of the flanges is
z3 equal to several thicknesses of the walls of the tube), are
z4 crucial to the rigidity of the tube against bending forces, which
i5 of course is an important consideration in a seat frame.
26
z~ A hole 63 for receiving the head-rest-support-tube is punched in
as the web 60 of the seat-frame-tube, in the manner as shown in Figs
zs 8a,8b. A die-button 64 is brought into contact with one side of
3o the web 60. A punch 65, carried in a stripper 67, is advanced,
3i and pierces the hole 63 in the web. The die-button 64 and the
3z stripper 67 are dimensioned to hold the web 60 to its desired
33 shape during the disruption caused by the punching operation and
34 subsequent stripping of the web from the punch 65.
36 The head-rest-support-tube 68 that is to be secured into the hole
3~ 63 in the web 60 is shown in Fig 9. The head-rest-support-tube
3e 68 is of steel, and includes an upper section 69, in which is cut
3s a notch 70, a first ring-bead 72, and a lower section 73, the
4o bottom section 74 of which is swaged down to a slightly smaller
4i diameter than the rest of the head-rest-support-tube. The inside
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1 diameter of the bottom section 74 is dimensioned to be a tight
2 location-fit on the peg 26 of the head-rest, and the reduced
s outside diameter of the bottom section 74 ensures an easy
4 placement of the head-rest-support-tube 68 into the hole 63 in
s the web 60 of the seat-frame-tube 50.
6
The manner of installing the head-rest-support-tube 68 into the
a hole 63 is illustrated in Figs lOa,lOb,lOc. The head-rest-
9 support-tube is first positioned into a punch unit 75. The top
to end 76 of the head-rest-support-tube abuts against a shoulder 78
11 of the punch 79, and the already-formed first ring-bead 72 abuts
12 against the bottom face of the punch-holder 80.
13
14 As shown in Fig 10b, the head-rest-support-tube passes through
is the hole 63, and the tapered bottom end of the head-rest-support-
ls tube enters the recess 82 in the die 83. As the punch 75 and die
1~ 83 approach, the bottom end of the head-rest-support-tube abuts
la against the bottom of the recess 82. From then on, further
19 approaching movement of the punch and die are reacted as an
2o axially-directed compressive force on the head-rest-support-tube.
z1 The compressive force is enough the cause the walls of the head-
22 rest-support-tube to buckle outwards, whereby the second ring-
23 bead 84 is formed. Approaching movement of the punch and die
24 continues until the condition of Fig lOc is reached.
2s The punch and die are then withdrawn, and the seat-frame-tube 50,
2~ with the head-rest-support-tube 68 now firmly attached, can be
ze transferred to the next stage in the manufacture of the seat.
29
3o The manner of attaching the head-rest-support-tube into the seat-
31 frame-tube ensures that the web 60 is structurally unitary with
32 the head-rest-support-tube. The first and second ring-beads
s3 72,84 grip the web between them, providing a secure base for
34 resisting abusive forces from any direction, which might tend to
disrupt the attachment.
36
s~ Hy forcing the punch unit 75 and the die 83 hard together
3e (Fig 10c) the amount of spring-back upon release can be made very
s9 small, whereby the compressive grip on the web is still firmly
4o present upon release.
41
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to
1 The head-rest-support-tube might be subjected to forces tending
2 to rotate it, during use of the automobile, and it is important
3 that rotation forces are resisted. If rotation of the head-rest-
4 support-tube were to be permitted, the movement might cause the
s attachment to rattle or work loose. Accordingly, the designer
s might prefer to make the hole 63 in the web slightly non-
circular. In fact, given the fact that the hole occupies a large
s area of the tube, it is all too easy for the hole 63 to be non-
9 circular in any event. The operation of forming the second ring-
to bead 84, however, ensures that the head-rest-support-tube adapts
11 itself completely to whatever out-of-roundness there might be in
12 the hole 63, which helps to ensure freedom from rotation of the
13 head-rest-support-tube.
14
is The attachment system as described is very strong, as compared
is with the conventional welded construction, but apart from that
1~ clear advantage, the attachment system provides excellent and
is repeatable accuracy. Now that accuracy of alignment of the two
19 head-rest-support-tubes can be relied upon, the design of the
2o head-rest detents can be free of the compromises needed with the
z1 conventional welded attachment; designing a detent is a matter of
z2 making sure the force to move the head-rest pegs against the
zs detent is neither too light nor too heavy, and the more
z4 accurately the components can be positioned, the easier it is to
zs ensure the correct force.
26
Not only is the attachment system as described very strong, and
zs accurate, but the system also lends itself to full automation.
Zs The attachment system is in keeping with the kinds of operations
so that have to be carried out on seat-frame-tubes, such as bending,
s1 piercing, etc, and the machinery for automating such operations
s2 is already commonplace. The similarity of those frame-tube
3s operations with the operations required in the attachment system
s4 will be clear: the dis-similarity of the frame-tube operations
ss with the conventional welding attachment system, is even more
ss clear.
CA 02235636 2000-OS-08
10a
"The expressions upper, lower, horizontal, vertical, etc, as used in this
specification,
should not be interpreted to mean that the invention only applies when the
actual physical
components used in operating the invention are orientated in only that way.
Rather, the
expressions should be taken as referring to those directions when the
components are
represented on paper, which is oriented accordingly."
