U.S. patent application number 09/437212 was filed with the patent office on 2002-05-09 for shock absorber.
This patent application is currently assigned to CONNOLLY BOVE LODGE & HUTZ LLP. Invention is credited to LOFGREN, OSCAR, SINTORN, TORKEL.
Application Number | 20020053493 09/437212 |
Document ID | / |
Family ID | 20413520 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020053493 |
Kind Code |
A1 |
SINTORN, TORKEL ; et
al. |
May 9, 2002 |
SHOCK ABSORBER
Abstract
A shock absorber is made with a bleed function and preferably a
non-return valve function associated with the bleed function. The
shock absorber has a cylinder (3) and, working in the latter in
working medium and arranged on a piston rod (4), a piston
arrangement. The latter comprises at least two first and second
pistons (5, 6) arranged at a distance from one another on the
piston rod. At least one piston (5) can, in connection with an end
position, be introduced into a first space so as, depending on its
position in or at the space, to bring about a modified or varied
damping force relative to when the piston is located outside the
space. The piston rod (4) is provided with an inner second space
(15) which is arranged so as to contain said bleed and/or
non-return valve function. Additionally or alternatively, the
piston (6) working outside the first space is provided with a
member performing a bleed function and with any associated
non-return valve function.
Inventors: |
SINTORN, TORKEL;
(TELEFONBRGGGAR, SE) ; LOFGREN, OSCAR; (SOLNA,
SE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ, LLP
1220 N MARKET STREET
P O BOX 2207
WILMINGTON
DE
19899
|
Assignee: |
CONNOLLY BOVE LODGE & HUTZ
LLP
|
Family ID: |
20413520 |
Appl. No.: |
09/437212 |
Filed: |
November 10, 1999 |
Current U.S.
Class: |
188/282.9 ;
188/304; 188/313 |
Current CPC
Class: |
F16F 9/064 20130101;
F16F 9/512 20130101; F16F 9/49 20130101 |
Class at
Publication: |
188/282.9 ;
188/304; 188/313 |
International
Class: |
F16F 009/56; F16F
009/26 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 2, 1998 |
SE |
9804165-0 |
Claims
1. A shock absorber provided with a bleed function which can or
preferably does interact with a non-return valve function, which
shock absorber has a cylinder and, working in the latter in working
medium and arranged on the piston rod (4), a piston arrangement
which comprises at least two first and second pistons (5, 6)
arranged at a distance from one another on the piston rod, at least
one piston (5) of which can, in connection with an end position, be
introduced into a first space (14) so as, depending on its position
in or at the space, to bring about a modified or varied damping
force compared with the case when the piston (5) is located outside
the space, wherein either the piston rod (4) is provided with an
inner second space (15) which is arranged so as to accommodate said
bleed function and any associated non-return valve function, and/or
the piston working outside the first space is provided with a bleed
function and any non-return valve function associated with the
latter.
2. The shock absorber as claimed in patent claim 1, wherein the
first space (14) is arranged in a cup-shaped or sleeve-shaped part
(13) which is located in said end position (3a).
3. The shock absorber as claimed in patent claim 1 or 2, wherein a
cup-shaped or sleeve-shaped part (13) is located in each end
position in the cylinder, and in that the first cup-shaped part
(13) serves the first piston in the first end position (3a), and
the second cup-shaped part serves a third piston in the second end
position.
4. The shock absorber as claimed in patent claim 1, 2 or 3, wherein
the first and/or the third piston has a sleeve-shaped part which,
in the end position in question, is involved in forming said first
space (14) in the end position concerned.
5. The shock absorber as claimed in any one of the preceding patent
claims, wherein the first space (14) is designed with a thickened
wall in the portion concerned of the cylinder wall.
6. The shock absorber as claimed in any one of the preceding patent
claims, wherein both a member (30) performing the bleed function
and a member performing the non-return valve function are arranged
in the second space.
7. The shock absorber as claimed in any one of the preceding patent
claims, wherein the member (30) performing the bleed function can
be controlled in order to obtain a bleed function which can be
regulated by controls.
8. The shock absorber as claimed in patent claim 6, wherein the
second space consists of a recess (15a) extending in the
longitudinal direction of the piston, at the first end of which the
member (30) performing the bleed function is arranged and in which
an operating rod (33) extending in the recess, toward the second
end of the recess, is arranged, which operating rod can be acted on
at said second end by means of an operating member (34).
9. The shock absorber as claimed in patent claim 6, 7 or 8, wherein
the member performing the non-return valve function is located
outside the member performing the bleed function, that is to say
closer to the free end of the piston rod in a case where the outer
piston (5) of the piston arrangement is arranged so that it can be
introduced into the cup-shaped or sleeve-shaped part (13).
10. The shock absorber as claimed in any one of the preceding
patent claims, wherein the second space (15) or recess is
connected, via one or more first passages or side holes (32) in the
piston rod wall, to the space (18) outside the outer wall of the
piston rod between the first and second pistons (5, 6).
11. The shock absorber as claimed in any one of the preceding
patent claims, wherein the second space or recess is connected, via
one or more second passages or side holes (31) in the piston rod
wall, to the space (23) outside the piston rod behind the second
(6) and, respectively, in front of the third piston.
12. The shock absorber as claimed in patent claim 10 or 11,
wherein, when an expansion movement takes place, the bleed function
is activated by virtue of the fact that working medium passes from
the upper side of the second piston, to each second passage or side
hole, onward via the member performing the bleed function, to each
first passage or side hole, and out at the lower side of the second
piston.
13. The shock absorber as claimed in patent claim 12, wherein, when
a compression movement takes place, the member performing the
non-return valve function prevents or acts on the bleed flow
flowing via the member performing the bleed function and thus acts
on/modifies the bleed function.
14. The shock absorber as claimed in any one of patent claims 3-8,
wherein the cup-shaped or sleeve-shaped part (13) is arranged with
a side gap (16) or side hole which preferably extends in the
longitudinal direction of the cylinder (3) and via which the
cylinder space (18) in front of the second piston (6) can be
connected by a duct or ducts to an accumulator container (8)
arranged separately in relation to the cylinder (3).
15. The shock absorber as claimed in any one of the preceding
patent claims, wherein the first or front piston (5), that is to
say the piston closest to the free end of the piston rod, has a
diameter which corresponds to the diameter of the first space and
is smaller than the diameter of the rest of the cylinder part, and
in that the first piston (5) is designed with first working medium
passages which can be activated essentially in the position of the
first piston in the first space and via which first working medium
passages the working medium then flows.
16. The shock absorber as claimed in any one of the preceding
patent claims, wherein the second piston has on the one hand a
diameter corresponding to the full-size diameter of the cylinder,
and on the other hand second working medium passages, at which
shims or shim packs (11, 12) are arranged on or at the lower and
upper sides of the second piston (6).
17. The shock absorber as claimed in any one of the preceding
patent claims, wherein a continuous damping-force regulation
function is afforded by means of the shims or shim packs (11, 12)
of the second piston, and increased end position damping is
effected by means of the position of the first piston (5) in or at
the first space (14).
18. The shock absorber as claimed in any one of the preceding
patent claims, wherein said shock absorber is intended to form part
of a motorcycle or a two-wheeled or three-wheeled vehicle.
19. The shock absorber as claimed in any one of the preceding
patent claims, wherein said shock absorber is intended to form part
of a car or a four-wheeled vehicle.
20. The shock absorber as claimed in any one of the preceding
patent claims, wherein the piston rod consists of a first piston
rod part (4a) which, at the front, is made with a part (4a') of
reduced diameter, on which the second piston (6) is mounted, and in
that the piston rod also comprises a second piston rod part (4b) of
bushing-like design, in which the part of reduced diameter
extends.
21. The shock absorber as claimed in patent claim 20, wherein the
shims or shim packs of the second piston on or at the upper and
lower sides of the second piston are secured by means of a
disc-shaped element (27) positioned between a transition/transverse
surface at the part of reduced diameter and the shim or the shim
pack (12) on the upper side of the piston.
22. The shock absorber as claimed in patent claim 20 or 21, wherein
an end surface on the second piston rod part (4b) bears against the
shim or shim pack on the lower side of the second piston, and in
that the second piston rod part bears the first piston with its
associated shim(s) or shim pack(s) on a spindle-shaped portion (4b)
of reduced diameter, at the end of which a securing member (28) is
arranged, for example a lock nut, so as to press together and hold
together the piston rod parts and the first and second pistons with
their associated shims or shim packs and also said disc-shaped
element.
23. The shock absorber as claimed in patent claim 20, 21 or 22,
wherein the first and second piston rod parts form portions of the
second space, and in that, in that portion of the second space
formed by the first piston rod part, a nozzle (30) with a seat is
positioned, which forms said member performing the bleed.
24. The shock absorber as claimed in any one of patent claims
20-23, wherein the first and second passages or side holes are
located on each side of the nozzle.
25. The shock absorber as claimed in any one of the preceding
patent claims, wherein the non-return valve function interacting
with the bleed function comprises a non-return valve which can be
acted on when an expansion movement of the shock absorber takes
place and, in the acted-on position, opens a passage for the bleed
flow.
26. The shock absorber as claimed in any one of the preceding
patent claims, wherein the non-return valve performing the
non-return valve function closes a passage for the bleed flow when
a compression movement of the shock absorber takes place.
27. The shock absorber as claimed in any one of the preceding
patent claims, wherein the non-return valve performing the
non-return valve function is provided with a cup-shaped part or a
cover part which has no bleed hole or is provided with one or more
bleed hole(s), the bleed flow being prevented from passing through
or being capable of passing through in a modified quantity for the
purpose of preventing or, respectively, modifying the bleed
function when compression takes place relative to when expansion
takes place.
28. The shock absorber as claimed in any one of the preceding
patent claims, wherein the members performing the bleed and the
non-return valve functions are positioned at each end of the second
part space (15b').
29. The shock absorber as claimed in any one of the preceding
patent claims, wherein the member performing the bleed and the
non-return valve function consists of a spring-loaded member, for
example a ball, arranged in the piston working outside the first
space, and, by means of a spring and medium pressure exerted, seals
against a seat when compression movement takes place, and is lifted
from the seat against the action of the spring by means of medium
pressure exerted when an expansion movement takes place, the bleed
flow being prevented or acted when compression takes place and
flowing when expansion takes place.
Description
TECHNICAL FIELD
[0001] The present invention relates to a shock absorber which
works with a bleed function. In this connection, the bleed function
can interact with a non-return valve function. In certain
embodiments, the shock absorber is preferably arranged so as to
have both the bleed and the non-return valve functions. The shock
absorber is also of the type which has a cylinder and, working in
the latter in working medium and arranged on the piston rod, a
piston arrangement which comprises at least two first and second
pistons arranged at a distance from one another. At least one of
said pistons can, in connection with an end position in the
cylinder or the shock absorber, be introduced into a first space so
as, depending on its position in or at the space, to bring about a
modified or varied damping force compared with the case when the
piston in question is located outside the space.
STATE OF THE ART
[0002] This type of shock absorber is previously known and
reference can in this connection be made to inter alia U.S. Pat.
No. 3,195,645. The present invention can be seen as a development
in relation to this known shock absorber. The known shock absorber
comprises a dual-piston arrangement in which the first or front
piston enters and exits a cup-shaped container so as to bring about
an increased damping force in the shock absorber end position
concerned. A second piston of full-size diameter is made with fixed
throttles via which the damping forces or damping capacity of the
shock absorber can be implemented in positions outside said end
positions. The known shock absorber also demonstrates that
increased damping force can be obtained in both the end positions
of the shock absorber.
[0003] Reference can also be made to UK Patent Specification 2 202
921 which indicates that, instead of a cup-shaped part which is
arranged in the shock absorber end concerned, use can be made of a
pin-shaped element which interacts with a recess in the piston rod
end and in this way acts on an arrangement which increases the
damping force via the shock absorber end concerned.
[0004] Reference can also be made very generally to European Patent
Specification 565 832 B1.
[0005] It is also known per se to arrange for a bleed function in a
shock absorber. What is known as return bleed is used in order to
make the wheels of the vehicle follow the surface of the ground
better. By arranging a bleed flow past a member which is arranged
on the piston in question and acts on the medium, forward, upward
and return (downward) movements are made easier. The use of a
non-return valve in the return bleed makes possible separation of
compression bleed and return bleed to different degrees, which can
be selected depending on the non-return valve selected.
DESCRIPTION OF THE INVENTION
[0006] Technical Problem
[0007] It is desirable to be able, in accordance with said U.S.
Patent Specification, to arrange a dual-piston arrangement of the
type disclosed also on those types of shock absorber which have on
the one hand a cylinder for a piston rod and a dual-piston
arrangement in working medium essentially in the form of hydraulic
oil, and on the other hand a container for an accumulator function,
which is connected to the cylinder via an intermediate part, a hose
or a pipe connection etc. In this respect, it is essential to be
able to arrange an appropriate bleed function, if appropriate
together with a non-return valve function, in the structure so that
an integrated construction which functions well is obtained. The
invention aims to solve this problem inter alia.
[0008] In the use of a bleed or non-return valve function, it is
often advantageous to be able to arrange the member performing the
bleed function so that regulatability or adjustability can be
achieved. It is to be possible to implement this adjustability by
means of members known per se in a manner known per se. The
invention solves this problem also.
[0009] As claimed in the present invention, it is also desirable
that dual-piston and bleed and non-return valve arrangements can
work with a piston function provided with shims, by means of which
a speed-dependent damping force function can be achieved. The
invention solves this problem also.
[0010] In connection with said UK Patent Specification, the
arrangement of a conical pin-shaped element involves a problem
associated with being able to use the interior of the piston rod
for mounting and positioning members which can effect said bleed
and/or non-return valve functions. The invention solves this
problem also and indicates a basic structure with a cup-shaped
element as claimed in said US Patent Specification or a
corresponding arrangement.
[0011] In connection with the device or shock absorber as claimed
in said UK Patent Specification, there is also a problem associated
with being able to clearly and unambiguously separate the functions
of the first and second pistons. As claimed in the invention, the
first piston is to be capable of effecting its end damping force
function without being influenced by the second piston. The
invention solves this problem also by proposing a basic concept
based on the US Patent Specification.
[0012] As claimed in the invention, seat and nozzle functions are
to be arranged for effecting said bleed function. The invention
solves this problem also and proposes in this connection a unique
arrangement for a piston rod, construction and arrangement of the
second piston with its associated shims and also construction and
arrangement of the first piston on the piston rod.
[0013] There is also a requirement to be able to use alternative
constructions and functions in connection with the bleed function
in a shock absorber of said type with a dual-piston arrangement and
shims arranged on the latter. The invention solves this problem
also and proposes an alternative or additional arrangement in which
the bleed function is separated from or integrated with the
non-return valve function.
[0014] The Solution
[0015] A shock absorber of the type described in the introduction
can be considered to be mainly wherein either the piston rod is
provided with an inner second space which is arranged so as to
accommodate said bleed function and any non-return valve function
arranged with the latter, or the second piston is made with a bleed
function and any non-return valve function interacting with the
latter.
[0016] In developments of the inventive idea, it is proposed that
said first space is to be arranged in a cup-shaped or sleeve-shaped
part which is located in said end position in question in the
cylinder or the shock absorber. In this connection, a cup-shaped or
sleeve-shaped part can be located in each end position in the
cylinder. The first cup-shaped part can then serve the first piston
in the first end position, and the second cup-shaped part can serve
a third piston in the second end position. Said first and/or third
piston can then have a sleeve-shaped part which, in the end
position in question, is involved in forming said first space in
the end position concerned. An alternative to forming the first
space with a cup-shaped part is to make the cylinder wall with a
thickened wall in the portion concerned.
[0017] In further embodiments, both a member performing the bleed
function and a member performing the non-return valve function are
arranged in the second space. In this connection, the member
performing the bleed function can be arranged so that it can be
controlled in order to obtain a bleed function which can be
regulated by controls. The second space can also consist of a
recess extending in the longitudinal direction of the piston rod,
at the first end of which the member performing the bleed function
is arranged and in which an operating rod extending in the recess,
toward the second end of the recess, is arranged. At said second
end, the operating rod can be acted on by means of a wheel or
equivalent adjusting member. The member performing the non-return
valve function is located outside the member performing the bleed
function, that is to say closer to the free end of the piston rod
in a case where the outer piston of the piston arrangement or the
first piston can be introduced into the cup-shaped or sleeve-shaped
part. The latter part can be arranged with a side gap or side hole
which preferably extends in the longitudinal direction of the
cylinder and via which the cylinder space in front of the second
piston can be connected by one or more ducts to an accumulator
container arranged separately in relation to the cylinder. The
second space or recess can also be connected, via one or more first
passages or side holes in the piston rod wall, to the space outside
the outer wall of the piston rod between the first and second
pistons. The second space can also be connected, via one or more
second passages or side holes in the piston rod wall, to the space
outside the piston rod behind the second and, respectively, in
front of the third piston. When an expansion movement takes place,
the bleed function is activated by virtue of the fact that working
medium can pass from the upper side of the second piston, to each
second passage or side hole, onward via the member performing the
bleed function, to each first passage or side hole, and out at the
front side of the second piston. When a compression movement takes
place, the member performing the non-return valve function prevents
the working medium flowing via the member performing the bleed
function. Alternatively, the non-return valve arrangement can act
on the passage for the working medium relative to when an expansion
movement takes place, it being possible to make the passage smaller
or larger.
[0018] In other developments of the inventive idea, the first or
front piston, that is to say the piston closest to the free end of
the piston rod, has a diameter which corresponds to the diameter of
the first space and is smaller than the diameter of the rest of the
cylinder part. The first piston is also made with first working
medium passages which are used essentially in the position of the
first piston in the first space. The working medium flows via the
working medium passages when the first piston is working in the
cup-shaped or sleeve-shaped part. The second piston has on the one
hand a diameter corresponding to the full-size diameter of the
cylinder, and on the other hand second working medium openings, at
which shims or shim packs are arranged on the lower and upper sides
of the second piston. A continuous damping-force regulation
function is therefore afforded by means of the shims or shim packs
of the second piston, and increased end position damping is
effected by means of the position of the first piston in or at the
first space. The shock absorber can be intended for use on a
motorcycle or a two-wheeled or three-wheeled vehicle. The shock
absorber can also be used to form part of a car or a four-wheeled
vehicle.
[0019] In one embodiment, the piston rod consists of a first piston
rod part which, at the front, is made with a part of reduced
diameter, on which the second piston is mounted. The piston rod can
also comprise a second piston rod part of bushing-like design, in
which the part of reduced diameter extends. Furthermore, the shims
or shim packs of the second piston on the upper and lower sides of
the second piston can be secured by means of a disc-shaped element
positioned between a transition at the part of reduced diameter and
the shim or the shim pack on the upper side of the piston. An end
surface on the second piston rod part can bear against the shim or
shim pack on the lower side of the second piston. The second piston
rod part bears the first piston on a spindle-shaped portion of
reduced diameter, at the end of which a securing member is
arranged, for example a nut (lock nut), so as to press together in
the axial direction and hold together the piston rod parts and the
first and second pistons and also the shims/shim packs of the
second piston and said disc-shaped element. In a preferred
embodiment, the first and second piston rod parts form portions of
the second space. In that portion of the second space formed by the
first piston rod part, a nozzle with a seat is positioned, which
forms said member performing the bleed. In this connection, the
first and second passages or side holes as claimed in the above can
be located on each side of the nozzle. In one embodiment, use is
made of a non-return valve which can be acted on by medium pressure
on compression and when it is acted on closes a passage for the
bleed flow. The non-return valve can have a bleed hole for said
flow. The bleed flow passes via the bleed hole when the valve has
closed said passage. In this way, different rates of bleed flow can
be obtained on expansion and compression. When there is no bleed
hole in the non-return valve, the bleed flow is prevented
completely. In a further embodiment, the bleed member and any
non-return valve member are positioned in the second piston by way
of an additional or alternative arrangement.
[0020] Advantages
[0021] By means of the above, an advantageous construction of the
shock absorber as such from an economic point of view is obtained.
The new functions can be built into a shock absorber which can be
of a type known per se, for example of the hlins Racing AB type of
shock absorber designated 46PRC, 46HR, 46R etc. The bleed and/or
non-return valve function can be adapted optimally to other
functions in the shock absorber. The shock absorber can thus be
provided with a bleed function and a non-return valve function
which function as claimed in the requirements of the customer. The
new functions can be built into modern shock absorbers such as
those of said type. In this connection, it is essential that shock
absorbers with accumulators can be provided with the new functions.
For example, it is to be possible for the bleed function to be
present when an expansion movement takes place in the end position
concerned, while it is prevented or acted on/modified when
compression movement takes place in said end position. When a
non-return valve is used, this can be arranged to have a bleed hole
for the bleed flow or can be without such a bleed hole, that is to
say the bleed function is prevented on compression. Alternatively,
non-return valves with bleed holes of different size for acting on
the bleed flow to varying degrees on compression can be arranged. A
non-return valve with a suitable bleed hole or without a bleed hole
is selected by testing. The selection depends on the travelling
position the driver wants for the vehicle. In the curve chart in
question, the bleed range is up to 0.4 m/s with variations upward
and downward in the speed range, depending on which shim pack and
bleed needle size are used. The selection depends on the situation,
the driver and the vehicle. On the shock absorbers available from
hlins Racing AB, 3.2 and respectively 4.0 mm return bleed needles
are used with nozzles. Quite generally, use is made of a larger
needle/nozzle and vice versa. With the bleed function, the damping
force is reduced around the zero range.
DESCRIPTION OF THE FIGURES
[0022] A for the present proposed embodiment of a shock absorber
which has the significant characteristics of the invention will be
described below with simultaneous reference to the appended
drawings, in which:
[0023] FIG. 1 shows in longitudinal section a shock absorber with a
cup-shaped element in the inner end position, where a first piston
in a piston arrangement on a piston rod takes up a position in the
space of the cup-shaped part during an ongoing compression
movement,
[0024] FIG. 2 shows in longitudinal section the shock absorber as
claimed in FIG. 1 but where the shock absorber has started to
perform an expansion movement,
[0025] FIG. 3 shows in longitudinal section, and in a simplified
and enlarged manner compared with FIGS. 1 and 2, a bleed and
non-return valve arrangement in the piston rod, which arrangement
is an alternative embodiment to that shown in FIGS. 1 and 2, in
addition to which a bleed flow is shown during the expansion stroke
of the shock absorber,
[0026] FIG. 3a shows a basic end view of the shock absorber parts
as claimed in FIG. 3,
[0027] FIG. 4 shows the shock absorber parts as claimed in FIG. 3
but in the case of a bleed flow which occurs on compression of the
shock absorber, and
[0028] FIG. 5 shows an alternative or additional embodiment of the
bleed function applied in the rear (second) piston of the shock
absorber.
DETAILED EMBODIMENT
[0029] The invention can be used on a shock absorber of the type
46PR, 46UR, 46R available from hlins Racing AB on the general
market. The shock absorber is well-known per se and comprises first
fastening and bearing parts 1 and second fastening and bearing
parts 2. Via the first bearing parts, the shock absorber is
connected to a chassis, while the second bearing parts are
connected to a wheel. The shock absorber comprises a cylinder 3 and
a piston rod 4 which works in the latter and has a piston
arrangement with a first piston 5 and a second piston 6. The shock
absorber is also provided with a main spring 7 and an accumulator
container 8 which is connected to the cylinder 3 via a connecting
arrangement 9.
[0030] The first piston is provided with one or more shim(s) 10 on
its upper side and, if appropriate, on its lower side also (not
shown), while the second piston 6 is provided with shims or shim
packs 11 and 12 on its lower side and, respectively, its upper
side. The cylinder 3 is provided at its end 3a with an internally
cup-shaped or sleeve-shaped element 13 which has a space 14, here
referred to as the first space. The piston rod is provided with an
inner space 15, here referred to as the second space. The second
space extends centrally and concentrically essentially throughout
the longitudinal direction of the piston rod. Arranged between the
cup-shaped part 13 and the inner wall 3b of the sleeve is or are
one or more side openings or side holes 16 which extend in the
longitudinal direction of the shock absorber parallel to the
central axis 17 of the shock absorber. By means of each side hole,
the space 18 in the cylinder, in front of the second piston 6, is
connected to the accumulator 8 via a duct system in the
intermediate part 9. The duct system connects the inner parts of
the container to said space 18 in a manner known per se. The
accumulator container 8 comprises a floating piston 8a which
separates a gas volume and a hydraulic oil volume inside the
container 8.
[0031] In FIG. 1, the first piston 5 is located in the recess 14.
The shock absorber is shown during an ongoing compression movement
in which the first piston is moving inward into the space 14
(toward the left in the figure). In this connection, a flow
direction for the working medium (hydraulic oil) is shown by the
arrow 19 and liquid passes the shim/shim pack 10 via one or more
openings 20 in the piston 5. The working medium flows from the
space 14, via the opening(s) 20, to the cylinder space 18 in front
of the second piston 6. This is provided with one or more
opening(s) 21, via which the medium 22 flows from the space 18 to a
space 23 in the cylinder, above the second piston. In doing so, the
medium passes the shim or shim pack 12. By means of the shim/shim
pack, a speed-dependent damping force is obtained in a manner known
per se.
[0032] When the first piston also takes up a position outside the
space 14, that is to say outside the cup-shaped part 13, the
damping force of the shock absorber is brought about essentially by
the second piston. When the first piston enters the cup-shaped
part, an increased end damping force function is obtained, which
depends on the dimensioning of the first piston with regard to the
opening(s) 20 and the shim(s) 10. The second piston occupies a
position outside the cup-shaped part the whole time.
[0033] FIG. 2 shows an expansion movement in the shock absorber end
position concerned, that is to say the first piston is moving out
of the space or toward the right in the figure. The medium
direction from the space 18 to the space 14 is shown by 24. In this
case also, the medium is acted on by the shim(s) on the first
piston and thus passes the shim damping through the opening(s)
concerned. In this direction, the shims do not produce any greater
damping force level on account of the cavitation risk in the space
14 (compare gas pressure.times.effective piston area). The medium
direction from the space 23 to the space 18 through the second
piston is shown by 26. This medium flow 26 is damped by the shim or
shim pack 11 on the lower side of the second piston.
[0034] The piston rod 4 as claimed in FIG. 1 is divided into two
piston rod parts 4a and 4b. The first part 4a is essentially
tubular and has a front part 4a' of reduced diameter. The second
piston rod part 4b is designed with a bushing-like shape and, at
the front, has the shape of a front spindle 4b' of reduced
diameter. The second piston is mounted on the part 4a' and its shim
or shim pack on the upper side is fixed by means of a disc-shaped
element 27 which bears against a stop surface 4a" on the first
piston rod part 4a. The first piston with its associated
shim(s)/shim pack(s) is mounted on the part 4b' which, at its outer
end, can interact with a locking member 28, for example a lock nut,
weld joint etc. The bushing-shaped second piston rod part presses
from underneath against the lower shim/shim pack of the second
piston. A connection 29 between the piston rod parts can consist of
a sliding connection. The parts and components shown are thus held
together by means of an axial locking force effected by the locking
member 28. The cup-shaped part 13 has an internal entry bevel 13a
for the first piston which, alternatively or additionally, can be
provided with a corresponding or similar entry bevel.
[0035] The second space 15 can be considered to consist of two part
spaces 15a and 15b, 15a extending in the piston rod part 4a and 15b
in the piston rod part 4b. In this connection, a nozzle 30 which
performs the bleed function is arranged in the recess 15a in the
front part 4a" of the piston rod part 4a. The part space 15a is
connected to the outside 4a" of the piston rod 4 and the space 23
above the second piston 6 via a passage or passages or a side hole
or side holes 31 in the piston rod wall. Said side hole(s) 31
open(s) directly above the disc-shaped element 27/the second
piston. The part space 15b is connected via a passage or passages
or a side hole or side holes 32 in the piston rod wall to the space
18 between the first and second pistons.
[0036] The above arrangement means that during the expansion
movement of the shock absorber as claimed in FIG. 2, the bleed flow
can flow between the space 23, via the member 30 performing the
bleed function and the part space 15b and the side hole(s) 32, and
the space 18.
[0037] Arranged in the second space is a rod 33 which extends to
the second end of the second space, at which the rod is arranged so
that it can be acted on by an operating member 34. In an exemplary
embodiment, the rod is displaced longitudinally depending on a
rotary movement of the member 34. The member 34 can be in the form
of a wheel. By means of the member and the rod, the bleed function
can be made regulatable or adjustable (in a manner known per
se).
[0038] FIG. 3 shows an alternative embodiment of the parts
concerned in detail. For the sake of clarity, only the front parts
of the piston rod (without pistons) have been included. A member
performing the bleed function is shown by 35. A part bearing a seat
36 is shown by 37. A front part 35a is tapered or conical and can
interact with the seat 36. In FIG. 3, the part 35 is shown in the
open position, while FIGS. 1 and 2 show the (corresponding) part in
the closed position. Depending on the position of longitudinal
displacement of the part 35 (35a), different quantities of bleed
flow 38 can pass between the part 35/35a and the seat 36. As
claimed in the above, the bleed flow passes via the passage(s) 26'
and into the space 15'. The member 35 performing the bleed function
can be of the same or similar design in FIGS. 1 and 2.
[0039] Arranged at the other end of the space 15b' is a non-return
valve 39 which acts on the bleed flow. The non-return valve
arrangement comprises a cup-shaped part 39a and a spring 39b. When
an expansion movement takes place in the shock absorber as claimed
in FIG. 3, the bleed flow moves the cup-shaped part 39 to the left
in the figure against the action of the spring 39a. This movement
or displacement results in side openings 40 (compare also FIG. 3a)
being exposed, and the bleed flow can pass out from the space 15b'
to outside the piston rod (compare the description above for FIGS.
1 and 2).
[0040] FIG. 4 shows the situation when the shock absorber performs
a compression movement. In this case, the spring 39b moves the
cup-shaped part 39a into a position in which the passages 40 are
closed. The cup-shaped part can be provided with one or more bleed
hole(s) 39c, via which the bleed flow 38' in the opposite direction
can flow from the outside of the piston rod into the space 15b',
via the seat 36 and the part 35a and out through the holes 26'
(compare also the description for FIGS. 1 and 2). Different
non-return valves can be provided with different numbers and sizes
of bleed hole(s). A selection can then be made from among various
non-return valves. In one embodiment, there are no bleed holes, and
the flow 38' is then prevented completely.
[0041] In FIG. 5, the second piston 6' is provided with openings 41
and 42, the opening 42 being provided with a seat formation for a
ball 44 (or equivalent member). The member 44 is pressed against
the seat by a spring 45 or equivalent element which is arranged in
the opening 42 and retained in the latter by means of a washer 46
(perforated washer).
[0042] When expansion takes place in the shock absorber and the
pressure above the piston 6' is increased or becomes greater than
the pressure below the piston, the member 44 is moved against the
action of the spring member 45, resulting in the bleed flow 38"
being brought about between the seat 43 and the member 44. On
compression, with the pressure conditions reversed on the upper and
lower sides of the piston 6', the member 44 closes against the seat
43, no bleed flow opposite to the flow 38" then being capable of
passing. Alternatively, the seat and/or the member 44 can be made
so as to allow an opposite flow of modified magnitude in relation
to the flow 38". Alternatively, a fixed passage can be arranged for
such an opposite flow.
[0043] The invention is not limited to the embodiment described
above but can be modified within the scope of the patent claims
below and the inventive idea.
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