Spring devices – Vehicle – Comprising compressible fluid
Reexamination Certificate
1999-04-06
2001-04-17
Oberleitner, Robert J. (Department: 3613)
Spring devices
Vehicle
Comprising compressible fluid
C267S064110, C267S064170, C267SDIG001, C280S006157
Reexamination Certificate
active
06217010
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus and a method of supporting a load (such as an automobile) that is subject to rapid weight fluctuations (due to braking, cornering, accelerating, pulling a trailer, etc.). The support is precisely matched to the weight of the load at each instant, and substantially eliminates both vibration and disturbance otherwise caused by road irregularities.
2. Description of the Related Art
Suspension systems in use today are compromised in their design due to the wide variety of conditions that they must accommodate. The weight of passengers and cargo varies widely, as do loads imposed by yawing, pitching, and rolling forces. Compromises have resulted in instability while cornering and/or braking, changing vehicle height under varying loads, and unchanging vehicle height at widely varying speeds. For example, great handling, sleek, low slung sports cars can be difficult to enter or exit and high load capacity trucks with elevated beds can be difficult to load and unload. Either the sports car or the truck driver may find it difficult to access drive up windows or automated teller machines.
Numerous designs have been proposed to alleviate problems and shortcomings with conventional suspensions. Some have advocated the use of complex sensors and control units (e.g. U.S. Pat. No. 5,037,128 to Okuyama et al., issued Aug. 6, 1991. Others have required the combined use of hydraulics, pneumatics, and electronics to relieve some of the symptoms of compromise (e.g U.S. Pat. No. 4,934,731 to Hiwatashi et al., issued Jun. 19, 1990). Most of the efforts to address the ideal suspension have been addressed in a piecemeal fashion. Several patents address forces generated while turning, accelerating, or braking (U.S. Pat. No. 5,566,970 to Lin, issued Oct. 22, 1996, U.S. Pat. No. 5,401,053 to Sahm et al., issued Mar. 28, 1995, and U.S. Pat. No. 4,573,702 to Klem, issued Mar. 4, 1986). Other patents addressed ride height controls as well (U.S. Pat. No. 5,222,759 to Wanner, issued Jun. 29, 1993, U.S. Pat. No. 4,867,474 to Smith, issued Sep. 19, 1989, or U.S. Pat. No. 3,831,969 to Lindblom, issued Aug. 27, 1974).
Citroën installed hydro-pneumatic suspensions in production cars, typified by the prior art shown in FIG.
1
A. The hydro-pneumatic suspension of
FIG. 1
comprises a hydro-pneumatic spring
1
A
10
that supports a portion of a vehicle frame
1
A
17
, which carries part of the vehicle load.
The pneumatic spring comprises a case consisting of a hollow cylindrical body, open at one end and having small, restricted openings
1
A
49
through a circular disk that otherwise closes the other end of the body. The cylinder is designed to contain fluid under pressure, and has an additional opening in the side of the cylinder near the closed end fluidly connected to a passage
1
A
35
. The restricted openings and side opening provide fluid paths for the admission or release of pressurized fluid from the cylinder. The exterior radial surface of the case has an integral step
1
A
12
which provides a bearing surface for the frame member
1
A
17
to rest.
The frame member
1
A
17
provides support for a load, such as a vehicle (not shown), whose weight is transferred by the frame member to the integral step on the exterior radial surface of case
1
A
16
.
A rod
1
A
19
is secured to and physically supports a piston
1
A
21
. The rod is a structural member which maintains a specified spatial relationship between the piston
1
A
21
and a wheel support
1
A
40
. The piston
1
A
21
slides within the interior bore of cylinder
1
A
16
yet maintains a pressure tight fit within the bore of the cylinder to provide a fluid seal between the cylinder
1
A
16
and piston
1
A
21
.
A variable volume chamber
1
A
33
is defined by the space within case
1
A
16
between piston
1
A
21
and the closed end of case
1
A
16
. The volume of the chamber
1
A
33
can be increased or decreased by forcing or releasing, respectively, pressurized fluid into the chamber through either the cylinder side opening or through the restricted openings. The variation in the volume of the chamber is reflected in the movement of piston
1
A
21
within the case
1
A
16
.
Passage
1
A
35
fluidly connects a valve (not shown) to the variable volume chamber through the cylinder side opening. The valve controls the admission of fluid into variable volume chamber
1
A
33
or the release of fluid from the chamber. Movement of fluid through passage
1
A
35
varies the length or separation of wheel support
1
A
40
relative to the case
1
A
16
and, thus, relative to the frame
1
A
17
under static conditions.
The wheel support
1
A
40
is secured to the end of rod
1
A
19
opposite piston
1
A
21
and configured to be secured to a wheel assembly to support the frame and its load relative to the ground.
A compressible gas
1
A
47
is contained within a pressure accumulator
1
A
84
. The compressible gas is isolated from the operating fluid in the lower half of the pressure accumulator and in variable volume chamber
1
A
33
by a membrane
1
A
51
. The expansion and contraction of the compressible gas results from movement of fluid through the restricted openings in the closed end of case
1
A
16
. The pressure accumulator
1
A
84
provides an air spring for the operation of the prior art suspension. When the wheel assembly encounters a bump, the wheel support, rod, and piston are all pushed up against the downward force of the load. This forces operating fluid up through the restricted openings, and compresses the compressible gas. Conversely, the compressible gas in the pressure accumulator forces fluid back into the variable volume chamber once the wheel assembly crests the bump, extending the piston back to its original position. The restricted openings
1
A
49
allow the operating fluid to pass between the pressure accumulator and the variable volume chamber at a predetermined rate.
A check valve
1
A
57
restricts fluid flows between the pressure accumulator and the case through the restricted openings.
A hydro-pneumatic spring similar to that shown in
FIG. 1A
has been used as an automotive suspension for a number of years. The vehicle is supported on the frame member
1
A
17
, which is in turn supported by a case
1
A
16
containing pressurized hydraulic fluid. The pressurized fluid is contained in a variable volume chamber
1
A
33
that is defined by case
1
A
16
and piston
1
A
21
. The piston can slide in the bore of case
1
A
16
while maintaining a pressure tight seal with the bore of the case. Pressurized fluid may be added or released from the variable volume chamber through passage
1
A
35
, raising or lowering the vehicle with respect to wheel support
1
A
40
. Fluid in the variable volume chamber is supported by piston
1
A
21
, which in turn is supported by wheel support
1
A
40
through rod
1
A
19
. Restricted openings
1
A
49
permit fluid flow between the variable volume chamber
1
A
33
and pressure accumulator
1
A
84
through check valve
1
A
57
. Fluid that flows into or out of the pressure accumulator displaces bladder
1
A
51
, causing compressible gas
1
A
47
to compress or expand.
The operation of the prior art fluid spring combined the features of an air spring (pressure accumulator
1
A
84
), a hydraulic level control (piston
1
A
21
and rod
1
A
19
moving within case
1
A
16
as fluid is admitted or released through passage
1
A
35
), and a shock absorber (restricted openings
1
A
49
and check valve
1
A
57
dampen the vertical motion of wheel support
1
A
40
). The fluid in variable volume chamber
1
A
33
both supports the vehicle at varying extensions of rod
1
A
19
and acts as a transmission medium between piston
1
A
21
and bladder
1
A
51
, causing compressible gas
1
A
47
to compress or expand as wheel support
1
A
40
absorbs bumps. In this manner the height of the frame member
1
A
17
is controlled, and road shock is isolated from it.
SUMMARY OF THE INVENTION
The Dynamic Load-Compensating Fluid Spring acts as a
Oberleitner Robert J.
Rader, Fishman, Grauer & McGarry An Office of Rader, Fishman & G
Sy Mariano
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