Title: Vibration damper
Abstract: Vibration damper, including a damping element and a pneumatic spring, wherein the damping element has a container tube, which is connected to a roll-off piston of the pneumatic spring. The roll-off piston is connected via an air suspension bellows acting as a rolling diaphragm to an external guide mounted concentrically and with freedom of axial movement with respect to the roll-off piston, the air suspension bellows and the roll-over piston forming the boundaries of a space filled with pressurized gas. The container tube is prepared for the installation of the roll-off piston by a non-cutting procedure suitable for mass production, wherein a length of tubing having the diameter of the container tube is mounted on a mandrel and clamped at both ends so that its length cannot change, and a pair of flow-turning/rotary-swaging rolls is pressed against the tubing and advanced toward each other to form an area of squeezed material. The rolls are then moved radially while being advanced axially over the area of squeezed material to form a first contour having a bevel, a cylindrical surface, and an axial stop for fitting the roll-off piston to the container tube.
Patent Number: 6,893,009 Issued on 05/17/2005 to Brehm, et al.
| Inventors:
|
Brehm; Stefan (Hennef, DE);
Brandhofer; Jörg (Eitorf, DE);
Müller; Michael (Hennef, DE)
|
| Assignee:
|
ZF Sachs AG (Eitorf, DE)
|
| Appl. No.:
|
755585 |
| Filed:
|
January 12, 2004 |
Foreign Application Priority Data
| Jan 22, 2003[DE] | 103 02 211 |
| Current U.S. Class: |
267/64.24; 267/64.21; 267/64.26 |
| Intern'l Class: |
F16F 009/04 |
| Field of Search: |
267/6421,642.4,641.6,641.9,641.7,641.1,642.7,641.3,642.5,642.6
72/370.13
29/434,243.523
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Siconolf; Robert A.
Assistant Examiner: Torres; Melanie
Attorney, Agent or Firm: Cohen, Pontani, Lieberman & Pavane
Claims
1. A vibration damper comprising:
a container tube formed with a circumferential first contour, said first contour
comprising a cylindrical surface formed with a circumferential groove and an axial
stop;
a roll-off piston fitted onto said cylindrical surface concentrically and in
a gas tight manner;
an external guide mounted concentrically and with freedom of axial movement relative
to said roll-off piston; and
an air suspension bellows connecting said roll-off piston to said external guide
and acting as a rolling diaphragm, said bellows and said roll-off piston forming
the boundaries of a gas space filled with a pressurized gas,
wherein said container tube is formed with a circumferential second contour having
a connecting area for the attachment of a second bellows.
2. A vibration damper as in claim 1 wherein said first contour comprises an area
of axially squeezed material produced by the flow-turning/rotary swaging process.
3. A vibration damper as in claim 2 wherein said area of axially squeezed material
forming said first contour is produced by a non-cutting process to obtain the cylindrical
surface, the circumferential groove, and the axial stop.
4. A vibration damper as in claim 1 wherein said second contour comprises an
area axially squeezed material produced by the flow-turning/rotary swaging process.
5. A vibration damper as in claim 4 wherein said area of axially squeezed material
forming said second contour is produced by a non-cutting process to obtain the
connecting area for the attachment of a second bellows.
6. A vibration damper as in claim 1 wherein said roll-off piston has an axial
end which abuts the axial stop of said circumferential first contour, said roll-off
piston having an inside diameter which is conically expanded at said axial end
to serve as an assembly aid.
7. A process for forming a container tube for a vibration damper comprising a
damping element and a pneumatic spring, said process comprising:
providing a machine suitable for flow-turning/rotary swaging of tubing;
providing a length of tubing with the diameter of the container tube;
mounting said length of tubing onto a mandrel and clamping both ends so that
said length cannot change;
pressing a pair of flow-turning/rotary-swaging rolls against said length of tubing
and advancing said rolls toward each other while rotating said mandrel, thereby
forming a first area of squeezed material; and
moving said rolls radially while advancing said rolls axially over said first
area of squeezed material to form a first contour having a bevel, a cylindrical
surface, and an axial stop.
8. A process as in claim 6 further comprising:
pressing said pair of flow-turning/rotary-swaging rolls against said length of
tubing and advancing said rolls toward each other while rotating said mandrel,
thereby forming a second area of squeezed material; and
moving said rolls radially while advancing said rolls axially over said second
area of squeezed material to form a second contour having a connecting area for
a bellows.
9. A process as in claim 8 further comprising precision turning said second contour
to correct the radii and fillets.
10. A process as in claim 9 further comprising precision turning said second
contour to correct the radii and fillets.
11. A vibration damper comprising:
a container tube formed with a circumferential first contour, said first contour
comprising a cylindrical surface formed with a circumferential groove and an axial
stop;
a roll-off piston fitted onto said cylindrical surface concentrically and in
a gas tight manner, said roll-off piston having an axial end which abuts axial
stop of said circumferential first contour, said roll-off piston having an inside
diameter which is conically expanded at said axial end to serve as an assembly
aid;
an external guide mounted concentrically and with freedom of axial movement relative
to said roll-off piston; and
an air suspension bellows connecting said roll-off piston to said external guide
and acting as a rolling diaphragm, said bellows and said roll-off piston forming
the boundaries of a gas space filled with a pressurized gas.
12. A vibration damper as in claim 11 wherein said first contour comprises an
area of axially squeezed material produced by the flow-turning/rotary swaging process.
13. A vibration damper as in claim 12 wherein said area of axially squeezed material
forming said first contour is produced by a non-cutting process to obtain the cylindrical
surface, the circumferential groove, and the axial stop.
14. A vibration damper as in claim 11 wherein said container tube is formed with
a circumferential second contour having a connecting area for the attachment of
a second bellows.
15. A vibration damper as in claim 14 wherein said second contour comprises an
area axially squeezed material produced by the flow-turning/rotary swaging process.
16. A vibration damper as in claim 15 wherein said area of axially squeezed material
forming said second contour is produced by a non-cutting process to obtain the
connecting area for the attachment of a second bellows.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to a vibration damper, comprising a damping element and
a pneumatic spring, wherein the damping element has a container tube, which is
connected to a roll-off piston of the pneumatic spring. The roll-off piston is
connected by an air suspension bellows acting as a rolling diaphragm to an external
guide, mounted concentrically and with freedom of axial movement with respect to
the roll-off piston. The air suspension bellows and the roll-off piston form the
boundaries of a space filled with pressurized gas.
2. Description of the Related Art
Vibration dampers of the type described above are used in motor vehicles,
in which they form part of the suspension which supports, for example, the driver's
cab of a commercial vehicle on the chassis to isolate the driver's cab as effectively
as possible from the vibrations introduced from the roadway into the chassis via
the wheel suspensions. The external guide of the pneumatic spring and the piston
rod of the damping element are connected to the cab, whereas the damping element
is connected by way of an attachment part to the chassis; the operation of the
pneumatic spring depends on its geometric dimensions, on the pressure prevailing
in the gas space, and on the profile of the roll-off piston, over which the air
suspension bellows rolls. The solution to the problem of sealing off the gas space
from the atmosphere all the way around the container tube, this gas space also
extending to the space around the piston rod, namely, by the use of an O-ring between
the roll-off piston of the pneumatic spring and the container tube of the damping
element, belongs to the state of the art. To divert the axial force component created
by the high pressure in the gas space into the container tube, the conventional
design provides an adapter ring, which requires a great deal of effort to manufacture
and which must be welded to the container tube. In addition, the O-ring is installed
in or near the adapter ring, which complicates the design and makes it more expensive.
A contour of the roll-over piston is supported axially against the adapter ring,
which absorbs the axially oriented forces of the pneumatic spring and diverts them
into the container tube. The larger the number of units produced, however, the
greater the need for rationalizing the means used to provide the above-mentioned
support and sealing of the roll-over piston on the container tube.
SUMMARY OF THE INVENTION
For the axial support of the roll-over piston on the container tube and for the
sealing of the roll-over piston against the container tube, the expensive adapter
ring is omitted and the container tube is provided with a first contour, which
makes it possible for the roll-over piston to be connected easily to the container
tube, and this connection is used simultaneously to connect the support to the
seal. For this purpose, the first contour has a circumferential, bead-like elevation
projecting beyond the outside diameter of the container tube, into which elevation
a bevel, a groove, a lateral surface, and a shoulder are integrated. The groove
is intended to receive a sealing ring, which rests against the inner surface of
the roll-over piston when this piston is pushed over the lateral surface of the
first contour on the container tube. During this assembly procedure, the end surface
of the roll-over piston will come into contact with the shoulder, whereby it assumes
a defined position, which is important to ensure that it will function properly.
The roll-over piston is provided with a conical expansion, which makes it possible
for the roll-over piston to be threaded cleanly over the bevel and to travel over
the sealing ring without damaging it or impairing its sealing function.
The container tube also has a second contour, the outside diameter of which extends
beyond that of the container tube and has a connecting area for a first end of
a bellows, the other end of which is attached to the external guide and which thus
protects the sensitive parts of the vibration damper, i.e., those which move against
each other during operation of the vehicle, from dirt. Because the gas space of
the pneumatic spring is always under pressure, it is merely necessarily to secure
the roll-over piston axially in place on the container tube of the damping element
in the direction pointing away from the pneumatic spring. The shoulder used for
this purpose, which is integrated into the first contour on the container tube,
projects beyond the outside diameter of the container tube and extends around the
circumference, whereby the production process used to realize this shoulder is
referred to as flow-turning or rotary swaging. This process makes it possible to
produce the desired form without actually cutting any metal and to obtain all of
the contours required for the connection of the roll-over piston to the container
tube with the precise dimensions required in a reproducible manner. The process
is suitable for mass production and, once the one-time investment for machinery
and equipment has been paid, is extremely low in cost. The process is described
in detail further below.
The invention presented here provides a vibration damper consisting of a damping
element and a pneumatic spring, in which an inexpensively manufactured container
tube of the damping element is designed in such a way that a roll-over piston as
a component of the pneumatic spring can be connected easily, with minimal assembly
effort, to the container tube while also meeting the requirements with respect
to leak-tightness and strength.
An exemplary embodiment of a vibration damper in which a roll-over piston of a
pneumatic spring is fixed axially in place on a container tube of a damping element
and simultaneously sealed is explained below on the basis of several drawings.
Other objects and features of the present invention will become apparent from
the following detailed description considered in conjunction with the accompanying
drawings. It is to be understood, however, that the drawings are designed solely
for purposes of illustration and not as a definition of the limits of the invention,
for which reference should be made to the appended claims. It should be further
understood that the drawings are not necessarily drawn to scale and that, unless
otherwise indicated, they are merely intended to conceptually illustrate the structures
and procedures described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a vibration damper including of a pneumatic spring and a damping
element, in which the roll-over piston of the pneumatic spring and a container
tube of the damping element are connected to each other;
FIG. 2 shows an enlarged view of the position of an end surface of the roll-over
piston with respect to a shoulder on the container tube and the position of a sealing
ring in a groove of a first contour;
FIG. 3 shows the container tube with the first contour and a second contour;
FIG. 4 shows a partial cross section of the first contour, consisting of a bevel,
the groove, a lateral surface, and a shoulder; and
FIG. 5 shows the second contour, which serves as a connecting area for a bellows.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
FIG. 1 shows a vibration damper, which includes of a damping element
1
and a pneumatic spring
3, wherein the damping element
1 has a container
tube
2, a fastening part
18, and a piston rod
19. The pneumatic
spring
3 includes an air suspension bellows
5, acting as a rolling
bellows; a prepressurized gas space
4; an external guide
7 connected
to the mass which is to be kept as free as possible of vibrations; and a roll-over
piston
6. The air suspension bellows
5 acts as an elastic element
which connects the external guide
7 to the roll-over piston
6, whereby
the air suspension bellows
5 rolls over a roll-over profile of the roll-over
piston
6 when the external guide
7 executes axial movement with respect
to roll-over piston
6; the air suspension bellows
5 thus assumes
the function of a spring as a result of the compression of the gas. A bellows
16
takes over the job of shielding important functional parts against dirt; one end
is connected to the external guide
7, whereas the other end is connected
by way of a connecting area
17 to the container tube
2.
FIG. 2 shows a partial, enlarged cross section of the area where the roll-over
piston
6 is attached to the container tube
2; that is, it shows how
the end surface of the roll-over piston
6 rests against a shoulder
10.
In the area of the end surface, a conical expansion
14 is provided on the
roll-over piston
6, the purpose of which is, first, to make it easier for
the piston to be the threaded over the bevel
9 and onto the lateral surface
11 of a first contour
8 during assembly and, second, to ensure that
a sealing ring
13, preferably designed as a toroidal sealing ring, installed
in a groove
12 in the first contour
8, is not damaged by sharp edges.
FIG. 3 shows a longitudinal section through the container tube
2, which
illustrates the design and the position of the first contour
8 and also
of a second contour
15. The second contour, with its previously mentioned
connecting area
17, is used for the installation of the bellows
16,
which can be attached there in a positive manner.
FIGS. 4 and 5 show how the first contour
8 and the second contour
15
are formed on the inside surface of the container tube
2, when the container
tube
2 is being produced by the flow-turning/rotary-swaging process. Here,
at least one roll/jaw is brought up against the unfinished container tube
2,
which has been pushed onto a mandrel and set to rotate, as a result of which the
tube material starts to flow under the high pressure of the roll/jaw. The material
is thus squeezed up in the direction in which the tool is fed. According to this
principle, the unfinished container tube
2 becomes thinner at the original
diameter and consequently thicker at the squeezed-up places, thus larger in diameter,
provided that it is clamped at the ends to the mandrel and prevented from changing
its original length. When the first contour
8 and/or the second contour
15 is being produced, it is advantageous to use two rolls, which are advanced
toward each other, so that the material is not only squeezed but also adjusted
to the proper dimensions at the same time. In this way, the first contour
8
can be produced with an accuracy which meets the functional requirements; that
is, the bevel
9, the groove
12, the lateral surface
11, and
the shoulder
10 can be produced with dimensions which are accurate enough
to ensure the proper joining of the roll-over piston
6 to the container
tube
2, the required overlapping of the two diameters, and the sealing function.
For special requirements, the radii and edges on the contours
8 and
15
can be finished by a final turning operation, but it is desirable to avoid this
for cost reasons.
A process is therefore proposed for the production of the container tube
2,
by means of which both a first contour
8 for the gas-tight attachment of
the roll-over piston
6 to the container tube
2 and a second contour
15 for the attachment of the folding bellows
16 can be formed, whereby
the following process steps will be used for the previously mentioned process of
flow turning/rotary swaging:
(1) a machine suitable for the flow-turning/rotary-swaging process is provided
for the flow turning/rotary swaging of tubing;
(2) a length of tubing with the diameter of the container tube
2 is clamped
onto a device;
(3) this length of tubing is mounted on a mandrel and clamped at least at one end;
(4) the mandrel supporting the length of tubing is rotated, and at least one
flow-turning/swaging jaw is brought into position;
(5) a groove
12 a lateral surface
11, a shoulder
10, and
a bevel
9 are formed on a first contour
8, and optionally a connecting
area
17 is formed on a second contour
15; and
(6) optionally the contours
8,
15 are precision-turned to correct
the radii or fillets.
The advantage of the invention over the state of the art is that the container
tube
2 is prepared for the installation of the roll-over piston
5
by a non-cutting procedure suitable for mass production, whereby a simple and lost-cost
operation joining the piston
6 onto the container tube
2 by pushing
against the shoulder
10 is sufficient to create one of the damping element subassemblies.
Thus, while there have shown and described and pointed out fundamental novel
features of the invention as applied to a preferred embodiment thereof, it will
be understood that various omissions and substitutions and changes in the form
and details of the devices illustrated, and in their operation, may be made by
those skilled in the art without departing from the spirit of the invention. For
example, it is expressly intended that all combinations of those elements and/or
method steps which perform substantially the same function in substantially the
same way to achieve the same results are within the scope of the invention. Moreover,
it should be recognized that structures and/or elements and/or method steps shown
and/or described in connection with any disclosed form or embodiment of the invention
may be incorporated in any other disclosed or described or suggested form or embodiment
as a general matter of design choice. It is the intention, therefore, to be limited
only as indicated by the scope of the claims appended hereto.
*
