Note: Descriptions are shown in the official language in which they were submitted.
~235157
This invention relates to a vibration damper
adapted to control the vibration between two members.
The invention is particularly suitable as, but not limited
to, a vibration damper for vehicle seats or the like.
The vibrations transmitted to a vehicle opera-
ion via his seat are a major contributor to operator
fatigue. This is particularly so in long distance trays-
port vehicles) farm and earth moving machinery, and power
boats.
To combat this problem, such vehicles are now
generally fitted with sprung seats, the seats having
adjustable dampers to damp the vibrations. While these
seats are an improvement, they are not totally satisfac-
tory as the dampers cannot be "tuned" or accurately set
to suit their particular applications and they generally
require an external reservoir for the oil employed as the
damping fluid or medium.
It is an object of the present invention to
provide a vibration damper which does not require an
external oil reservoir.
It is a preferred object to provide a damper
where the degree of damping in both directions can be
independently controlled.
It is a further preferred object to provide a
damper which can be readily adjusted by means of external
controls.
It is a still further preferred object to pro-
vise a damper which can be easily assembled and main-
twined.
According to the invention there is provided
a vibration damper including a damper body formed of a
first and second similar parts clamped together in a face
to face relationship to define a bore of which opposite
end halves are defined by the two parts; a closed Solon-
don formed in the bore of said damper body by sealing
means disposed axially within the bore at opposed ends
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of the bore within said first and second parts; a piston
rod passing axially through said sealing means and said
closed cylinder; a piston means, supported on said pus-
ton rod and movable therewith in said cylinder, said
piston means being sealingly engaged against the wall of
said closed cylinder to divide said closed cylinder into
two variable volume chambers; a damping fluid filling
said chambers; passageways defined in said body parts
to form a pair of fluid passages interconnecting the two
chambers and respective one way valve means within each
of said pair of fluid passages to provide unidirectional
flow, in opposite directions, of the damping fluid through
the passages; and independently controllable valve means
in each passage to control the flow of the damping fluid
lo through the passages and thereby control the damping of
the piston means in each direction, said independently
controllable valve means each comprising a metering plug
within its respective passage on a rotatable shaft which
passes through the damper body transversely of its rest
pective passage.
The body may be mounted on a fixed frame or
support and the piston rod connected to a movable member,
or vice versa, or the body and piston rod may be connected
to a pair of relatively movable members.
Further features of the invention will be
apparent from the following description with reference
to the accompanying drawings, in which:
FIG. 1 is a front view of a vibration of the
damper, parts being broken away for clarity;
FIG. 2 is a sectional plan view taken on line
2-2 in FIG. l;
FIG. 3 is a sectional side view of an embody-
mint of vibration damper in accordance with the invention;
and
FIG. 4 is a sectional end view of one of the
control valves taken on line 4-4 in FIG. 3.
.
By
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Referring to FIGS. 1 and 2, the damper has a
rectangular base plate lo provided with mounting holes
11 adjacent each corner. A circular outer cylinder 12,
forming the damper body, is mounted on the base plate lo
and welded thereto to close its lower end. A circular
inner cylinder 13, of reduced diameter, is similarly
mounted on the base plate lo and the annular space 14
formed between the two cylinders forms a reservoir for
the oil used as the damping fluid.
lo The upper end of the annular space is closed
by an annular plate 15 sealable secured to the upper ...
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ends of the two cylinders 12, 13. A cover plate 16,
has a central bush 17 and an annular flange 18, is
secured to the annular plate 15 by studs 19. A central
bore 20 is provided in the bush 17, and fitted with a
pair of neoprene seals 21 to sealable engage the piston
rod 22 of a piston 23 slid ably movable in the inner
cylinder 13, dividing the latter into upper and lower
variable volume chambers 24, 25 respectively.
A pair of neoprene piston rings 26 seal the
piston 23 to the inner wall of the inner cylinder.
A pair of fluid passages 27, 28 are provided
adjacent the inner cylinder 13, being formed by square
section tubes closed by the base plate 10 and annular
plate 15. Fluid conduits 29, 30 connect the lower
chamber 25 to the passages 27, 28 respectively, while
conduits 31, 32 connect the upper chamber 24 to the
passages.
A one-way valve 33, having a spring loaded
ball 34 and valve seat 35, allows the oil to pass from
20 the lower chamber 25, through fluid passage 27, to the
upper chamber 24 when the piston 23 moves down the inner
cylinder. A similar valve 36, with ball 37 and valve
seat 38, allows the oil to flow from the upper chamber
24 to the lower chamber 25 via passage 28, the valves
25 33, 36 preventing flow of the oil in the opposite direct-
ion.
The flow of oil through the passages 27, 28
and thereby the damping applied to a body connected to
the piston rod 22, is controlled by respective control
30 valves 39, 40.
Referring to the control valve 39, a rectangular
hole is formed in the outer side wall of the passage 27
to slid ably (and sealable) receive a valve block 41
which is movable transversely across the passage 27 to
35 vary the effective cross-sectional area of the passage.
235~S7
The block 41 has a central bore which screw thread-
ably receives a threaded spindle 42. A seal block
43, with neoprene seals 44, is formed integrally with
the spindle 42 and is sealable mounted in the seal
housing 45 formed in the outer cylinder 12. The outer
end of the spindle is of square cross section and
engaged in a complementary hole formed in a control
nut 46. By rotating the nut 46, the block 41 moves
along the spindle 42 to open and close the passage.
Control valve 40 is similar to the control
valve 39, with a valve block 47 selectively varying
the effective area of the passage 28.
A bypass valve 48 is connected to the passage
27 via a hole 49 to enable oil under pressure to be
bled to the reservoir 14, while an intake valve 50,
connected to the passage 28 via a hole 51, allows the
oil from the reservoir to enter the passage.
The operation of the damper will now be
described.
The base plate 10 is secured to a frame e.g.
a vehicle chassis and the piston rod 22 to a vehicle
seat (not shown).
It will be assumed that the piston 23 is in
the position shown in FIG. 1. When the piston 23 is
forced downwardly (i.e. on its downstroke), the volume
of the lower chamber 25 is reduced, oil flows out of
conduit 29 into the passage 27 (the flow into passage
28 being prevented by the onepway valve 36). The
bypass valve 48 remains closed and the oil flows
through the restriction in the passage formed by the
valve block 41, through the one-way valve 33 and
conduit 31 to the upper chamber 24.
The piston rod 22 effectively reduces the
volume of the upper chamber 24 and so the decrease in
the volume of the lower chamber 25 is not matched by
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the increase in volume of the upper chamber 24.
The pressure of the oil in the passage 27 increases,
it unseats the bypass valve 48 and oil flows through
the hole I to the reservoir 14.
On the upstroke of the piston, valves 33 and
48 are closed but one-way valve 36 is opened to allow
oil to flow from the upper chamber 24 to the lower
chamber 25 via the passage 28, the rate of flow (or
degree of clamping) being controlled by the restriction
in the passage formed by the valve block 47.
As the increase in the volume of the lower
chamber 25 it greater than the decrease of the upper
chamber 24, the intake valve 49 opens to allow fluid
to enter the passage 28 from the reservoir 14.
As the flow of oil between the chambers
follows different paths on the up - and down strokes,
the adjustment of the control valves 39, 40 allows the
damping on each stroke to be independently controlled,
and the degree of damping on each stroke can be from
0% - 100%. The bypass valve 48 and intake valve 49
allows the oil to flow between the reservoir and the
inner cylinder, maintaining both chambers full of oil.
In a modified form of this embodiment (not
shown), the valve blocks 41, 47 are rotatable, but
non-axially, movable on the spindles and the nuts 46
of the control valves 39, 40 are screwthreadably mount-
Ed on the seal housing 45. As the nuts 46 are rotated,
they move inwardly or outwardly relative to the outer
cylinder, respectively, closing or opening the passages
27, 28.
While circular cylinders 12, 13 have been
shown in the drawings, these may be substantially
square in plan, if preferred. In addition, the passe-
goes 27, 28 may be spaced from inner cylinder 13 and
connected thereto by short tubes forming the conduits
.,
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29-32.
The removable cover plate 16 enables the
piston 23 to be withdrawn and the damper serviced.
However, the cover plate 16 and annular plate 15 may
5 be made in one piece and the damper sealed for life,
the oil acting as a lubricant.
Turning now to the second embodiment of FIGS.
3 and 4, the damper 60 has damper body 61 formed by
two body halves 62, 63 secured together by bolts 64
which pass through the length of the body.
A central cylinder 65 is formed in the body
61 and is closed at each end by a respective stainless
steel insert 66. Each insert has a peripheral flange
67 located in a recess at the respective ends of the
15 cylinder.
A bronze bearing or bush 68 is fitted in each
insert 66 and aligned co-axial bores 69 are provided
through the pairs of inserts 66 and bearings 68.
A piston rod 70 is slid ably journal led in the
20 bronze bearings 68 and extends from each end of the
body. A series of neoprene o-rings 71 are provided
in the bearings 68 to provide a fluid-tight seal
between the rod 70 and the bearings 68.
A piston 72 is provided in the cylinder 65 and
25 has its hub 73 fixed to the piston rod 70. A piston
ring 74 around the periphery of the piston seals the
piston to the inner wall of the cylinder 65. As
shown, the piston 72 divides the cylinder 65 into
two variable volume chambers 75, 76.
: 30 A pair of passages 77, 78 in the body 61
interconnect the chambers 75, 76. Referring to
passage 77, a ball 79 co-operates with a valve seat
80 to provide a one-way valve 81, the ball 79 being
seated on the valve seat 80 when the oil seeks to flow
from the chanter 76 to chamber 75 but being unseated
lZ35~57
to allow unrestricted flow from chamber 75 to
chamber 76. A similar one-way valve 82 is provide
Ed in passage 78 to limit the flow of the oil in
the direction of chamber 76 to chamber 75.
The flow of oil through the passages, and
thereby the damping of a body or member connected to
the piston rod 70, is controlled by respective control
valves 83, 84. Referring to control valve 83, this
has a shaft 85 rotatable journal led in the body 61
and sealed thereto by an o-ring 86. A square head
87 on the outer end of the shaft 85 is adapted to
receive an operating handle or lever (not shown).
Referring to FIG. 4, the shaft 85 has a
reduced diameter portion, aligned with the passage
15 77, forming an eccentric metering plug 88. By rotate
in the shaft 85, the plug 88 selectively opens and
closes the adjacent ports 89, 90 of the passage 77
to control the flow of oil through the passage.
In FIG. 4, the plug 88 is shown intermediate
its closed and open positions and so the degree of
damping would be approximately 50% ( the shaft 83
being rotatable through approximately button its
opened and closed positions).
A small clearance 91 is provided to ensure
25 that some flow of oil is always possible through the
passage 77 to prevent the travel of the piston 72.
The operation of the damper will now be
described.
The body 61 may be mounted e.g. on a seat
frame and one end of the piston rod 70 connected to
one of the legs of a spring-loaded, scissor-type
support frame.
As the piston rod 70 moves the piston 72 to
reduce the volume of oil in chamber 75, the flow of
oil through passage 78 is prevented by the one-way
lZ35157
valve 82 and so the oil can only flow to the chamber
76 via passage 77. The ball 79 of the one-way valve
81 is unseated and the oil flows through the control
valve 83 at a rate determined by the position of the
plug 88 relative to the ports 89 or 90. When the
piston 72 is moved in the opposite direction, the oil
is transferred between the chambers 76 and 75 at a rate
controlled by the control valve 84.
While the control valves 83, 84 are shown on
opposite sides of the body 61, it is preferred that
they are provided on the same side with their control
handles or levers adjacent each other.
In a modified form of this embodiment (not
shown) only one fluid passage may be provided where
the intermediate portion of the passage is separated
into two parallel branches, each having a one-way valve
and control valve to provide controlled unidirectional
flow in each branch.
It will be readily apparent to the skilled
addressee that various other types of control or
metering valves may be employed to control the degree
of damping and one example is a needle valve.
The damper can be used in a wide range of
applications where the vibration of a body relative
to a datum, or between a pair of relatively movable
bodies, is required to be damped.
Various changes and modifications may be made
to the embodiments described without departing from
the scope of the appended claims.
Jo
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