Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
937
SEAT RECLINING MECHANISM
The present invention relates to a seat reclining
mechanism.
In our U.K. Patents 1528357 and 1586869 we disclose
a seat reclining mechanism which includes a cushion arm
pivotally connected to a squab arm by a planetary gear
arrangement. The planetary gear arrangement includes a
pair of ~ide by side ring gears, one being secured to the
squab arm and the other being qecured to the cushion arm.
A sun gear is provided which is in driving connection
with both ring gears via a plurality of planet gears. The
pitch of teeth in each of the ring gears is different so
that rotation of the planet gearq causes relative
rotation between the ring gears.
The planet gears float and it is necessary for there
to be an acceptable amount of tolerance between the gear~
in order to enable ~mooth operation. Unfortunately such
tolerance al~o results i~ pivotal play between the qquab
and ¢ushion arms.
In accordance with one aspect of the present
invention such play iq substantially reduced or
eliminated by incorporating at least one sun gear having
a frusto-conical form, the ~un gear being bia~ed in an
axial direction so as to urge the planetary gears in a
radially outwards direction and into contact with the
ring gears. Accordingly pivotal play between the qquab
arm and cuQhion arm is substantially reduced or
eliminated.
Preferably a pair of sun gears are provided, both of
which are sub~tantially of fruqto-conical form, the pair
o~ ~un gear~ being arran~ed with their ~maller diameter
axial ends facing one another and such that they are
located on opposite axial qides of the planetary gears.
The bia~ing means are arranged such as to urge the two
sun gears axially toward one another. Thiq may be
~
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achieved by having one sun gear a~ially fixed and the
other axially movable or both sun gears may be axially
movable.
Preferably three planetary gears are provided which
are equally spaced about the internal circumference of
the ring gears. Three planetary gears are preferred since
such an arrangement ensures that each ~un gear will apply
an equal radial loading on each planetary gear. However
it is to be appreciated that more than three planetary
gears may be provided if necessary.
- The mechani~m may also include at least one support
member for the planetary gears of the type disclosed in
our U.K. patent 1586869. Thus the support member would
include for each planetary gear a concave surface. The
support member ensures that the planetary gears maintain
their circumferential spacing and also restrict radially
inward movement of each planetary gear.
Pre~erably the in¢luded angle between the inclined
peripheral faae of each un gear and its axis is small,
~or example in the range 2 to 15'.
Preferably, the sun and planetary gears have
involute teeth. This facilitates smooth operation of the
mechanism.
Various aspects of the present invention aré
hereinafter described with reference to the accompanying
drawings, in which:-
Figure 1 is a schematic perspective view of avehicle seat including a seat reclining mechanism
according to the present invention;
Figure 2 i8 a schematic end view of a seat reclining
mechani~m according to the present invention;
Figure 3 i8 a more detailed sectional view taken
along line X-X in Figure 2; and
Figure 4 is a part sectional view taken along line
Y-Y in Figure 2.
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Figure 5 is a view similar to Figure 3 of an
alternative embodiment according to the present
invention.
The seat reslining mechanism 10 of the present
invention is used to pivotally connect a seat back or
squab 8 to a seat cushion 7. Two mechanisms 10 are used
per seat, one being located on either side of the seat
(only one of which is visible in Figure 1) and each
mechanism 10 includes a ~quab arm 13 secured to the frame
~not shown) of the squab and a cushion arm 15 secured to
the frame Inot shown) of the cushion. The mechanisms are
both driven by a handle 9.
In the embodiment illustrated in Figures 2 to 4 of
the drawings, the mechanism includes a first ring gear 12
which ~orms part o~ the ~quab arm 13 (only part of which
is visible in Figure 2) and a second ring gear 14 which
~orm~ part of a cushion arm 15 (only part of which is
vi~ible in Fi8ure 2). The 3quab and cushion arms are more
~ully illustrated in our U.K. patents 1528357 and
1586869.
The squab and cushion arms are preferably formed
~rom metal plate and the ring gears 12, 14 are preferably
formed by a pressing operation. The pre~sing operation
provides o~fset wall portions 13a, 15_ which together
with the internal walls of the ring gears define a
housing for the ~un and planetary gear~ 16 and 18
respectively.
As seen in Figure 2, three planetary gears 18 are
provided which are equi-~paced about the internal
circumference of the ring gears 12, 14.
As seen in Figure 3, the sun gear 16 is mounted on a
drive shaft 20 and is located 80 as to be slightly offset
to one axial side of the planetary gears 18.
The ~un gear 16 is located on the drive shaft 20 so
as to be rotatable therewith and bears against a shoulder
22. The shaft 20 projects through wall portion 13_ to
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receive a waQher 24. A spring 25 i~ located between the
washer 24 and wall portion 13_ to urge the shaft 20 in an
axial dire~tion ~o a~ to urge the sun gear 16 further
inbetween the planetary gears 18.
A~ ~een in Figures 3 and 4 the sun gear 16 is of
generally frusto-conical ~hape with its narrow end facing
the direction of bias caused by ~pring 25. Thus as the
sun gear 16 is urged further inbetween the planetary
gears it has the effect of urging the planetary gears
radially outward and into urged contact with the ring
gears 12, 14. The angle of inclination of the peripheral
wall of the sun gear 16 i8 preferably about 5O to 10-.
The strength of the ~pring 25 is chosen to ensure
that the biasing force i8 greater than the force
8enerated by rotating the drive ~haft during adjustment
and which tend~ to ur~e the 8ear axially out of
en8a8ement with the planetary gear~. This ensures that
the planetarY gear~ are ur~ed radially outwardly during
adjustment o~ the mechanism a~ well a~ when the mechani~m
i~ atati¢.
It is envisaged that the edges of the planetary
géar~ 18 may be chamfered slightly to a~sist axial entry
o~ the ~un gear 16 without interfering with the rolling
action of the gears.
It will be seen in Figure 1 that the gear profiles
are involute. This provide~ for smooth operation of the
mechaniqm ~ince the planetary gear~ and ring gear~ are
maintained in rolling contact. If de~ired however the
gear profiles adopted in our U.K. patent 1528357 and
1586869 may be used.
In Figure 5 there is illustrated an alternative
embodiment 100 in whioh 2 sun gear~ 16a,16b are provided.
Embodiment 100 i~ a modi~ication o~ the embodiment 10 and
2imilar parts have been designated by the same reference
numerals. In the embodiment o~ Figure 5 both sun gears
16_, 16_ are ~lidably mounted on the drive ~haft 20 and
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are urged axially toward one another by associated coiled
cpring~ 110. As for the spring 25, the strength of
springs 110 are chosen to provide a bia~ing force greater
than the force tending to urge the gears out of axial
engagement which i~ generated by rotating the drive
shaft.
The drive ~haft 20 includes a main portion 20a which
extends through and projects either side of the hinge
assembly. The main portion 20_ is preferably fluted to
define in cross-section a star shape ~see Figure 2). At
one side of the hinge assembly the main portion 20_ is
provided with a shoulder 121 which is preferably formed
integrally with the main portion 20a. A coil spring 110
is ¢ompressed between the shoulder 121 and sun gear 16a.
This has the effect of biasing sun gear 16a in an axial
direction toward sun gear 16k.
At the opposite side of the hin~e assembly the main
portion 20_ is provided with a boss 125. The boss 125
includes an internal bore 126 which has a portion having
a cross sectional shape complimentary with the main
portion 20a and so is rotatable in uniqon therewith. The
boss 125iis provided with a shoulder 127 which prevent~
axial movement toward the sun gear 16b and i~ prevented
from being axially withdrawn from the shaft portion 20a
by me~ns of a clip 128 secured to the main shaft portion
20_.
The boss 125 includes a shoulder 130 and a coiled
spring 110 is compressed between shoulder 130 and sun
gear 16b. This ha~ the effect of bia~in~ the ~un gear
16b in an axial direction toward sun gear 16a. The boss
125 includes an external flat 131 and ser~es a~ a support
for connection of the handle 9 for effecting rotation of
the drive shaft 20.
Each sun ~ear 16_, 16_ has a central bore having a
cross-sectional shape complimentary with the cross-
sectional shape o~ the shaft portion 20a which enables
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each sun gear to slide axially along the main shaft
portion 20a and yet be rotationally ~ixed relative
thereto. Preferably the star shape of the main shaft
portion 20a and sun gear bore is chosen to have the ~ame
number of star arms a~ the number of teeth as the sun
gear, the star arms being being radially aligned with the
teeth. This facilitates ensuring that both sun gears
16a, 16_ are correctly aligned during assembly of the
mechanism.
However it will be appreciated that other cross-
sectional shapes of the main ~haft 20a may be adopted if
desired, ~uch as for example a polygonal shape.
Preferably the off-set wall portions 13_, 15_ are
provided with further off-set portions 13 ,15_ which are
designed to be spaced from gears 16_, 16b by a limited
distance ~d' which is chosen to limit axial outward
movement o~ sun gears 16_, 16_ so as to ensure that
me~hing eneagement between the sun and planetary gears is
maintained in the event o~ one or both springs 110
~ailing. Similarly in the embodiment o~ Figure 2, sun
gear 16 is ~paced from a further wall portion 15b to
maintain meshing engagement with the planetary gears in
the event o~ ~ailure of 3pring 25.
If desired a support member 200 (shown in broken
lines in Figures 2,3 and 5) may be included. The support
me~ber has concave depressions 201 in each of which a
planetary gear is seated. The depressions 201 in the
support member 200 serve to restrain radial inward
movement of the planetary gears.
As illustrated in the drawings, three planetary
gears 18 are preferred. This is because three is the
minimum number o~ gears which can be acted upon by the
sun gear~s) to ensure that the sun gear(s) apply an equal
load to all planetary gear~ irrespective o~ the
concentricity o~ the ring gears 12,14 and/or the
circularity of each ring gear 12,14.
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If a larger number of equally spaced planetary gears
18 are to be used, preferably the number is chosen such
that no two gears are diametrically opposed ie an odd
number of gears is chosen.
In the embodiments described above and illustrated
in the drawings, the pivotal movement between the squab
and cushion arms is defined and supported by the gear
system, ie by the intermeshing of the sun, planetary and
ring gears and there is no separate journal for
supporting the pivotal movement. It will be appreciated
however that the squab and cushion arms could be
pivotally corrected by journal formations and that the
sun, planetary and ring gears be utilised to cause
relative rotation about the pivot only.
