ARRANGEMENT FOR ADJUSTING THE DAMPING FORCE OF A SHOCK ABSORBER

TRADUCTION NON-DISPONIBLE

English Abstract

ABSTRACT OF THE DISCLOSURE
Apparatus for adjusting the damping force of a hydraulic
telescopic shock absorber to provide a greater increase of the damping
force at increasing piston speeds. The apparatus comprises a piston
which separates two cylinder chambers with a system of passages in
the piston for passage of the damping medium from one chamber to another.
This system is closed when the shock absorber is in the rest position
by a spring loaded valve having an adjustment member. The passages
closed by the valve each de bouch separately on the valve and have
separate inlets which can be closed successively by an adjusting member.

Claims

WHAT IS CLAIMED IS:
A hydraulic telescopic shock absorber having a cylinder
closed by a cylinder cap and filled with a damping medium
in which a piston having a piston head and a piston rod is
riciprocatingly arranged, said piston head dividing the
cylinder into two portions and further provided with a
plurality of longitudinally extending and circumferentially
spaced passages extending therethrough, the passage openings
on the lower surface of the piston head being closed by a
- 3a -

- 4 -
ring-shaped resilient valve, a rigid pie-shaped closing
member coaxially and movably mounted about the piston rod on
the upper surface of the piston head, said closing member
including a longitudinally extending adjustment tab which
engages an adjustment pin fixedly mounted to the lower
surface of said cylinder cap, and wherein said passages are
selectively opened or closed by extending the piston rod until
said pin engages said tab and thereafter rotating the piston
rod to expose the desired number of passages.
- 4 -

Description

il(~Z834
A~lw~G~MI~r I~Ol~ AWU';'I'lNG ~1~1ll` DAML~ING F~RC~ OF A S}IOCK A~SOR~E~.
The invention relates to an arrangement for adjusting the
damping force of a hydraulic telescopic shock absorber having a
system of passages for the damping medium which is closed in the
rest position of the shock absorber by means of a spring loaded valve
and in which an adjusting member is provided, acting upon the passage
system so as to control the damping force of the shock absorber.
Such arrangement is known from Dutch Patent 85 643. In this
prior art arrangement the damping force is adjusted by varying the
tension of the valve spring by means of the adjusting member which to
this end acts upon the valve spring. This way of adjusting the damping
force has the drawback that a substantially constant variation of the
damping force is provided, in other words that the damping force/speed
curves remai~ substantially in parallel at various adjusting positions.
It is therefore an object of the present invention to provide
an adjusting device for which the damping force variation a'ways remains
substantially proportional to the piston speeds, however that the
proportionallity factor at the successive adjusting steps gradually
increases.
The arrangement according to the present invention is charac-
terized in that the passages closed by the valve each debouch separately
on the valve and moreover possess separate inlets which can be closed
successively by the adjusting member.
It has been shown that by this measure the increase of the
damping force is greater in proportion as the piston speed increases.
The arrangement according to the present invention will now
be explained further with reference to an embodiment shown in the
related drawings in which:
Fig. 1 shows a graph of the relation between the damping
forces and the piston speed as provided by the arrangement according
to the present invention;
Fig. 2 shows a partial longitudinal sectional view of a
hydraulic telescopic shock absorber in which an adjusting device accor-
ding to the present invention is arranged, and
Fig. 3 shows a sectional view along the line III-III in Fig. 2.

~1~2~34
Referring to Fig. 1 line 1 shows the relation between the
damping force F and the piston speed V in a first adjusting position
of the arrcangement.
~ The increase of the damping force is substantially propor-
tional to the increase of the piston speed.
Line b shows the variation in damping force in a second
adjusting position in which the initial damping force is raised from
ai to bi and an increase in piston speed corresponds with a further
increase in damping force.
A prior art shock absorber would show a relation according
to the dotted line b , in which the increase of the initial damping
force bi ~ ai does not increase further at higher piston speeds.
In a next adjusting position, referring to lines c and c and
the damping force ci, the same applies as in relation with the lines
b and b and the initial damping force bi. The number of adjusting
positions can be arbitrary.
The arrangement according to the present invention provides
a more progressive adjustment i.e. a greater increase of the damping
force at increasing speeds than the prior art arrangement. It will be
appreciated that if a same high damping force at the same high piston
speed would be chosen in the prior art arrangement as in the arrange-
ment according to the present invention the damping forces at low
piston speeds would raise out of proportion.
In an embodiment of the adjusting arrangement according to
the present invention Figs. 2 and 3 show a cylinder 1 of a hydraulic
telescopic shock absorber filled with damping medium in which a piston
2 and a piston rod 3 are reciprocatingly arranged.
The piston rod 3 extends through a cylinder cover 4. The piston
2 divides the cylinder 1 into two rooms 5 and 6 and is provided with
passages 7 which can interconnect both rooms and which are closed in
the rest position of the shock absorber by a ring-shaped resilient valve
8 on the side of the cylinder room 6.
The inlets of the passages 7 lying at the side of the cylinder
room 5 can be covered or not by a closing member 9, which to this end
is provided with a portlon 10 having an enlarged radius.
-- 3 --

- C. de Kock - 6
The closing member 9 is also provided with an adjusting
lip 11, while an adjusting pin 12 is arranged in the cylinder
cover 4.
The operation is as follows:
During the outgoing stro~e of the piston damping medium
is forced out of the cylinder room 5 through passages 7 into
cylinder room 6. Hereby the resilient valve 8 will be opened
under influence of the pressure of the damping medium at the
outlets of said passages 7, the inlets of,which are not
- covered by the closing member 9. The closing of more or less
passages 7 can be accomplished by first bringing the piston
2 by means of the piston rod 3 in the end position at the
side of the cover and by then rotating the piston rod such
that the adjusting lip 11 abuts against adjusting pin 12
preventing the adjusting member 9 from further rotation
when the piston rod 3 is additionally rotated so as to have
covered a lesser or greater number of passages 7.