Note: Descriptions are shown in the official language in which they were submitted.
WO94/21~7 215 8 5 ~ 9 PCT/AU94/00134
TITLE: "VEHICLE SEAT SUSPENSION UNIT"
BACKGROUND OF THE INVENTION
1. Field of the Invention
THIS INVENTION relates to a vehicle seat
suspension unit. In particular, it relates to a
"decelerator" or damper for such a sus~n-c;on unit.
2. Prior Art
In International Application Nos.
PCT/AU90/00144 (WO 90/11841) and PCTIAU92~00647 (WO
93/10996), we disclosed vehicle seat suspPnci~n units
where a single transfer assembly transfers the spring
force to the seat platform at a varying rate.
SUMMARY OF THE ~N-l INVENTION
It is an object to provide a ~mpi ng means
where there is substantially zero damping about an
initial preset seat height but where the ~mp; ng
increases as the deflection of the seat from the preset
height increases.
It is a preferred object to provide a unit
which allows an overall reduction in spring rate which
in turn provides an increase in isolation efficiency.
Other preferred objects will hPc~mP apparent
from the following description.
Throughout the specification, a vehicle seat
suspension unit "of the type defined" shall be used to
include a susp~n-cinn unit having:
a base frame mountable on a vehicle;
a seat support frame to mou~t an operator's
seat;
a scissor arms assembly interronn~rting the
frames to enable the frames to move relative to each
other substantially in par~llPli .cm;
a transfer assem~ly pivotally mounted on one
of the frames, having at least one arm engaging the
other of the frames; and
WO94/21~7 215 8 5 4 9 PCT/AU94/00134
spring means mounted on the one frame and
connected to the transfer assembly.
In one aspect, the present invention resides
in a "deceleration" or damping unit for a vehicle seat
suspension unit ~eg. of the type ~efine~) inc~ i nq
a brake slide plate having a longitll~i n~l
slot at or adjacent one end thereof and a hole at or
adjacent the other end;
an anchor pin passing through the hole and
mounted on one frame of the vehicle seat suspencion
unit;
resilient ring or washer means about the
anchor pin received within the hole to allow at least
limited ~uov~uent of the brake sli~e plate relative to
the anchor pin;
a pivot pin on a tr~nC~er ~cc~mhly 0~ the
vehicle seat sUsp~nci nn unit pA-C-Ci ng throu~h the s~ot
and arranged for ~ v~l,.e~l~ within the slot subs~nt;~l1y
parallel to the longitn~;n~ ;s of the brake slide
plate;
at least one brake disc or washer interposed
between the transfer assem~ly and the brake slide plate;
and
means to apply a clamping or frictional load
between the brake disc or washer and the brake slide
plate;
so arranged that when the vehicle seat
suspension unit is displaced in an initial small
distance from a preset position, the brake slide plate
moves relative to the anchor pin to provide
substantially zero ~m~; ng, but on further ~i.cr1~r~m~ntr
the brake slide plate is moved relatively to the pivot
pin and a substantially constant damping force is
generated between the brake slide plate and the brake
disc or washer.
W094121~7 215 8 5 19 PCT/AU94/00134
Preferably, the damping force is substantially
constant throughout the full range of displacement from
r the initial small distance.
Preferably, the damping force may be
5 selectively set by varying the ~Amping force applied
between the brake slide plate and the brake disc~s) or
washer(s). Belleville springs or compre~i nn washers
may be provided on the pivot pin to transfer the damping
force from an adjustable nut on the pivot pin to the
lO brake slide plate and brake disc~s) or washer~s).
Preferably, the hole is slightly eccentric,
being preferably non-circular and formed by two circles
with spaced centres.
Preferably, when the vehicle seat susp~ncinn
15 unit is displaced, the initial small distance, the brake
slide plate and pivot pin mo~e in 11ni~Qn but on furth_r
displacement, the brake slide plate Pn~ An~ is
restrained from further .lluv~llel~L by the anchor pin and
the brake slide plate moves relative to the pivot pin.
In a second aspect, the present invention
resides in a vehicle seat suspension unit of the type
defined fitted with the "decelerator" or ~Am~i ng unit.
BRIEF DESC~RIPIION OF TE~E DRAWINGS
To enable the invention to be fully
2S understood, a preferred embodime~t will now be descri~ed
with reference to the ~ccnmpAnyin~ dr~ ng~ in whi~h:
FIGS l and 2 are side views of the vehicle
seat suspension unit in its raised and lowered
positions, respectively;
3 0 FIGS 3 and 4 are sectional side views of the
unit correspon~ing to FIGS 1 and 2, respectively, with
parts omitted for clarity;
FIG 5 is a front view of the transfer
assembly, with one of the springs and one ~Am~i n~ unit
3 5 shown in ~h~ li n~s;
WO94Q1~7 PCT/AU94/00l34
2~s~5 ~9
FIG 6 is a side view corresponding to FIG 5;
FIG 7 is a side view of the brake plate when
assembled; and
FIG 8 is a sectional top view of the damping
unit when installed.
DETAITFn DESCRIPT~ON OF ~ ~K~KK~ ~MR~ N'l'~
The vehicle seat susp~nc~ nn unit 100 has a
bottom frame 110 (with side rails 111) and a top rame
112 (with plate 113) interconnected by a sC;ccor arms
assembly 114 for relative ILlOv~u~,t suhstantially in
parallelism (ie. see WO 90/11841) and WO 93/10996). The
bottom frame llQ is bolted to the seat Cli~C~ fixed to
the vehicle floor, and the operator's seat is secured to
the top frame 112 ~see in particular WO 93~10996).
A tr~nsfer ass~mhly 115 has a tubular bQdy 116
journalled on an axle 116a inter~nn~ting brackets 117
on the side rails 111 of the bottom frame 110.
A pair of transfer arms 118 extend from the
body 116 and SU~Ol L the axle 119 for rollers 120 which
bear on the underside of the plate 113 on the top frame
112.
Two springs 121, anchored at one end to the
bottom frame 110, are connected to respective pairs of
brackets 122 ext~nA; n~ below the tubular body 116 of the
transfer assembly 115. By selective ad~u~L~uL of the
anchoring of the coil sprin~s 121 (eg. by an
electrically driven ad~u~"~uL unit 123), the Sus~nc; on
unit 100 can be preset to a given ride height for the
seat which sets a datum.
A respective pair of links 124 are pivotally
connected to the side ra~ls 111 of the bott~m frame 110
and have pins 125 s1; ~Ahl ~ in slots 126 in the side
rails 127 of the top frame 112. The links 124 limit the
forward disp~ m~nt of the top frame 112 relative to
the bottom fr~me 110 if the v~hi~lP should be involved
WO94121~7 215 8 5 ~ 9 PCTIAU94100134
in an accident and so the links 124 assist in securing
the seat from ~re~ki ng away from the vehicle.
The damping unit 10 will now be described.
A respective anchor pin 11 passes through each
side rail 111 of the bottom frame 110 ~nd through a boss
12 on a bracket 117. The anchor pin 11 is fitted with a
nut 14.
The pin 11 passes through an O-ring 15 (see
FIG 7) in an elongate hole 16 in a planar brake slide
plate 17. (The hole 16 is formed by two circles with
offset centres and allows limited ~o~ t of the brake
slide plate 17 relative to the anchor pin 11 along the
longitll~;n~l axis of the brake slide plate 17.)
(Washers 18 may be provided to allow low friction
~l~o~llent of the brake plate 17 between the boss 12 and
the lower end of the inner -cc;~cnr arms 124 of the
scissor assemhly 114.) The lower ends of the in~er
scissor arms 124 are slotted, with the anchor pins 11
passing through the slots 125 and the arms 124 are
supported for low friction on the ~n~h~r pins 11 by
bearings 126.
A respective pivot pin 19, with head 20, is
supported by a respective pair of brackets 127 at each
end of the tubular body 16 and pass through an elon~Ate
slot 21 along the longittl~i n~ 1 axis of the ~rake c1;~
plate 17.
A pair of fibre brake washers 22 are
interposed between the ~rake slide plate 17 and brackets
127 and a damping force thereon is provided by a nut 23
and a pair of Belleville spring washers 24. As the
brake slide plate 17 moves relative to the pivot pin 19
and the fibre brake washers 22 a constant friction is
generated between the brake p~ate 117 and the brake
washers 22.
At the datum height of the seat, the ~nchor
WO 94/21487 PCT/AU94100134
2~5~5~ 6
pin 11 is intermediate the hole 16 in the brake slide
plate 17 (see FIG 7). For small initial displA~m~nts
of the suspension unit 100, the brake slide plate 17
will move relative to the anchor pin 11 without the
latter engaging a side of the hole 16. ~The O-ring
compression softens any initial impact when the anchor
pin 11 engages either side of the hole~16.) There is no
,llo~l,ent of the brake slide plate 17 relative to the
pivot pin 19 as the brake slide plate 17 moves in llni.co~
with brackets 127 on the transfer assembly 115.
If the displacement of the suspension unit lQ0
causes the brake slide plate 17 to engage the Anchor pin
11 on one side of the hole 16, then further displAr~m~nt
causes the anchor pin 11 to restr~i n the brake slide
plate 17 and thereby pull (or push) the brake slide
plate 17 relative to the brackets 31 on the transfer
assemhly, and also relative to the brak wA.ch~r~ 22.
The constant rate friction generated between the brake
slide plate 17 and ~rake washers 22 creates a
decelerating or damping force to oppose the displA~m~nt
and this damping force will also be generated as the
suspension unit re~urns to (or passes) the datum
position. (On the return stroke, the brake slide plate
17 will move so that the anchor pin 11 will engage the
opposite side of the hole 16.)
It will be readily apparent to the .~kill~
addressee that the decelerator or ~A~;ng unit 10
provides substantially zero ~Amr; ng about the datum ~ie.
zero displ~cement) p~sition of the S~ n~i on unit 100
but will provide substantially constant ~Amri ng once a
preset disp1 A~ L is e~ee~. This enables very
high isolation of the seat from the VPh ~ to be
achieved, whilst having only a very low spring rate in
the springs 121.
Various changes and mo~ifi~A tions may be made
21585~9
PCT/AU94/00134
~ WO94/21487
to the embodiments described and illustrated without
departing from the scope of the present invention
defined in the appended claims.
