Note: Descriptions are shown in the official language in which they were submitted.
A device for locally adjusting the
tension of an elastic sheet, in particulax
or a vehicle seat
Users of motor vehicles no longer hesitate to-day
to travel long distances. Unfortunately, there often
results considerable physical fatigue, and in particular
pains due to the compressing of the vertebrae brought
about by the prolonged maintenance of the body in the
same position.
An object of the present invention is to overcome
this state of affairs by providing a device for locally
adjusting the tension of an elastic sheet more particu-
larly adapted to the adjustment of the seat back of avehicle, which permits a modification of the firmness
ox the support provided locally by the elastic sheet
and thus a limitation of the fatigue of the user.
The invention therefore provides a device for adjust-
ing the tension of an elastic sheet which comprises a flatspring having end portions which are each fixed to two
parallel surfaces between which surfaces a rotary disc is
inserted, the two discs being connected to rotate together
but being inclined in the opposite direction so that their
rotation pivots in opposite directions the parallel sur-
faces of the two ends of the spring and results in a
modification of the length and the curvature of the spring.
Thus, depending on the position of the rotary discs,
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the flat spring is displaced between an extreme position
in which it is taut and stiff and a compressed bent
extreme position corresponding to maximum flexibility.
Between the two positions, the spring is flat at rest
and this results in its normal elasticity.
The flat spring may easily be associated with an
elastic sheet to which it transmits the tension or the
bending imparted thereto by the discs.
Preferably, the spring is a flat sinusoidal spring
of the same type as those making up the elastic sheet.
The rotary discs are mounted on a control rod with
which they are connected to rotate and on which they are
inclined.
Such a device is particularly adapted to the adjust-
ment of the support in a motor vehicle seat. It isthen preferably mounted in a lombar support region, the
control rod being fixed to the uprights of the frame of
the seat.
It will of course be understood that the elastic
sheet may comprise a plurality of adjustment devices per-
mitting a local modification in its tension in accordance
with needs.
A description of an embodiment,which is given merely
by way of a non-limiting example and shown in the accom-
panying drawings, will bring out the advantages and fea-
tures of the invention.
In the drawings :
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Fig, l is a front elevational view of the end por-
tions of the device according to the invention, in its
position of rest ;
Fig. 2 is a top plan view of the device shown in
Fig. 1 ;
Fig. 3 is a diagrammatic view from below of the
device in its bent position ;
Fig. 4 is a diagrammatic view of the device shown
in Fig. 3 whose spring has been eliminated ;
Fig. 5 is a view similar to Fig. 3 of the device in
the stiffening position ;
Fig. 6 is a view similar to Fig. 4 of the position of
the discs when the spring is stiffened ;
Figs. 7, 8 and 9 are views of the control discs
lS respectively in the positions correspondinq to Figs. l,
3 and 5 ;
Fig. lO is a perspective view ox a portion of the
elastic sheet of the seat back of a vehicle provided with
an adjusting device according to the invention.
~0 As shown in the drawings, the device according to
the invention comprises a flat spring l, preferably having
a sinusoidal shape, the two end portions of whlch each
carry a case 2, 3, fixed by a plate 4 to thè spring and
enclosing between its opposed lateral walls respectively
6 and 8 a disc lo, 12. The two discs 10 and 12 are fixed
on a rod 14 with respect to which they are inclined in
opposite directions, as clearly shown in Fig. l. The two
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discs 10 and 12 are identical and are thus placed in a
symmetrical manner relative to the median plane of the
rod 14 .
In the position of rest, i.e. the position shown in
Figs. 1 and 2, the discs 10 and 12 are not in contact
with the walls 6, 8 of the cases so that they exert no
force against these walls. In fact, the walls 6 and 8
have the shape of a reclining V whose apices 16, 18 are
in facing relation and define consequently a narrow
passage whose width is slightly greater than the thickness
of the discs 10, 12. The inclination of the sides 20 of
the Vs of the walls 6 and 8 substantially corresponds to
the inclination on the rod 14 of the discs 10, 12 which
are thus simply interposed between the two lateral walls
of the correspondlng case.
Each of the walls 6, 8 is provided with an opening
22 which allows the free passage of the rod 14 and even
the rotation of the latter without driving the Vs of the
walls 6 and 8.
Consequently, when the rod 14, which is preferably
provided with a control knob 24 which has not been shown
in Figs. 1 to 6, rotates about its axis and drives the
disks 10 and 12, the latter rub against the apices
16, 18 of the lateral walls 6, 8 and tend to urge back
the two walls of each case in opposite directions. The
cases pivot on the rod 14 so as to converge either in the
direction of the spring 1 or in the opposite direction.
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For example, if the rod 14 rotates in the clockwise
direction as vlewed ln Fig. 1, the discs 10 and 12 gra-
dually assume the position shown in Figs. 3 and 4, i.e.
tend to urge the walls 8 toward their end fixed -to the
spring 1 while they urge outwardly the end of the walls
opposed to the spring 1. This results in a bending of
the spring 1 in the direction of the rod 14 and at the
same time a shortening of this spring.
The spring 1 thus bent of course has an increased
flexibility. Inversely, if the rod 14 is turned in the
counter-clockwise direction, the discs 10 and 12 assume
the position shown in Figs. 5 and 6. In this case, each
of the discs urges outwardly the wall 6 at its end fixed
to the spring 1 while the two discs bring closer together
the ends of the walls 8 opposed to this spring 1. The
sprlng is consequently taut and extended while assuming
a curvature whose concavity faces the rod 14. The ex-
tension of the spring stiffens it and reduces its elas-
ticlty~
Preferably, each of the cases 2 and 3 includes on
the plate 4 for fixing to the spring 1 a projection 26
whlle the discs 10 and 12 define two teeth respectively
28 and 30 facing in opposite directions. The coopera-
tion of the teeth 28 and 30 with the projection 26 limits
~5 the displacement of the corresponding disc 10 or 12 and
consequently provides a signal indicating the arrival
of this disc in its extreme position. Indeed, when the
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device is in the inactive position shown in Figs. 1 and 2,
each of the discs is in the position shown in Fig. 7.
The projection 26 of the case is substantially at equal
distances from each of the teeth 28 and 30. Consequently,
S the rod can turn without difficulty in either direction
and rotate the discs fixed thereto. Depending on the
direction of rotation of the rod 14, the tooth 28 approa-
ches the projection 26 and comes into abutment there-
against (Fig. 8) or the tooth 30 approaches the projec-
tion 26 and comes into abutment thereagainst (Fig. 9).
In each of these two last-mentioned positions, the
disc 10, 12 has slightly passed beyond its unstable
position and consequently tends to assume the following
stable position consfituted by the position offset 180
relative to the initial stable position shown in Fig. 7,
i.e. to continue its rotation. The disc is therefore
solidly urged against the projection 26 and locks itself
in the position given thereto. Only a rotation of the
rod 14 can change the position of the discs 10 and 12
and the spring 1.
Such a device permits, owing to the association of
the spring 1 with an elastic sheet, a local modification
of the tension of this sheet by varying the curvature and
the length of the spring 1.
The elastic sheet may be made in various ways and
may be employed in a seat, a box mattress or in any other
application. The adjustment is however particularly
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important in the case of vehicle seat backs such as that
partly shown in Fig. 10.
In this case, the rod 14 is mounted in apertures 34
formed in the vertical uprights 36 constituting the frame
s of the seat and to which the elastic sheet 38 is secured.
The device is thus shown behind the elastic sheet, the
spring 1 forming a transverse element of this sheet and
being fixed by wire hooks 40 to the longitudinal springs
of the sheet 38.
The spring 1 is thus in contact with the various
springs. In the position of rest of the device, the
spring 1 has no action on the springs of the elastic
sheet. On the other hand,when it is stiffened under
the action of the discs 10 and 12 and reaches the position
shown in Figs. 5 and 6, it puts the springs 42 of the
sheet 38 under tension and stiffens the seat back in the
region in which it is located. on the other hand, when
it is shortened and bent in the opposite direction, it
imparts an additional elasticity to the whole of the sheet.
Preerably, an adjusting device of the type described
hereinbefore will be mounted in the lombar support region
which is the region the most subject to a compressing of
the vertebrae when using a vehicle seat. However, it will
be understood that this adjusting device may easily be
mounted in any other position and that even several
adjusting devices may be mounted on the same seat back.
In this way, the user is in a position to adiust at any
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moment the firmness of the support he receives and adjust
it each time he desires.
Likewise, the rod 14 may be rectilinear as shown in
Fig. lo, or be bent in its central part, as shown in
Figs. 1 to 6, or even have any other shape enabling it
to cause the rotation of the discs 10 and 12 and the
deformation of the spring 1 without affecting the action
of the elastic sheet 38 itself.
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