Self-pumping hydropneumatic shock absorbing strut with internal level regulation

Self-pumping hydropneumatic shock absorbing strut with internal level regulation, in particular for motor vehicles, with a work cylinder which is filled with oil, is under the pressure of at least one gas cushion which is located in at least one high pressure chamber and acts as a spring. The work cylinder is divided by a piston carried on a hollow piston rod into two work chambers, with a piston pump which is driven by the spring movements and transports oil from a low pressure chamber into the work chamber which is connected to the high pressure chamber. The pump cylinder of the piston pump is formed by the hollow piston rod. There are valves between the work chamber and the high pressure chamber for the decompression and compression damping, whereby as a valve, there is at least one valve plate, which interacts with a valve seat, which is located on the work cylinder.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a self-pumping hydropneumatic shock absorbing 
strut with internal level regulation, in particular for motor vehicles, 
with a work cylinder which is filled with oil and is under the pressure of 
at least one gas cushion which is located in at least one high pressure 
chamber and acts as a spring. The work cylinder is divided by a piston, 
which piston is carried on a hollow piston rod, into two work chambers, 
with a piston pump which is driven by the spring movements and transports 
oil from a low pressure chamber into the work chamber. The work chamber is 
connected to the high pressure chamber, and the pump cylinder of the 
piston pump is formed by the hollow piston rod, whereby there are valves 
between the work chamber and the high pressure chamber for the 
decompression and compression damping. 
2. Background Information 
In similar shock absorbing struts, as described in German Patent No. 14 30 
536, for example, the piston which is fastened to a piston rod, divides 
the work cylinder into two work chambers, whereby the piston rod is 
realized so that it is hollow, thereby forming a piston pump, and a pump 
rod is inserted in the cavity of this piston rod. On the end surface of 
the work cylinder there is a solid base which holds the pump rod 
elastically, and whereby this base also contains damping valves for the 
decompression and compression damping. These valves are illustrated only 
schematically, without a more detailed illustration of the concrete 
construction or realization. 
OBJECT OF THE INVENTION 
The object of the invention is to create a structurally simple valve unit 
for the decompression and compression damping of a self-pumping 
hydropneumatic shock absorbing strut. 
SUMMARY OF THE INVENTION 
The invention teaches that this object can be accomplished if, as the 
valve, there is at least one valve plate which interfaces with a valve 
seat which is located on the work cylinder. 
In one embodiment which is favorable from a manufacturing point of view, 
the valve plate can be supported radially inwardly on a second valve seat 
which can be located on a pump rod. 
On self-pumping, hydropneumatic shock absorbing struts with internal level 
regulation in which a pump rod is not used, the invention teaches that the 
valve plate can be supported radially inward on a second valve seat, which 
second valve seat can be supported radially inwardly on a retaining 
element. The retaining element can be connected to the work cylinder, and 
straddles or bridges the work cylinder. 
On the constructions described above, it can be advantageous that either 
the valve seat can be formed only between the valve plate and the work 
cylinder, in which case degressive characteristics can be achieved as a 
result of the large valve seat diameter, or also that a second radially 
inward valve seat can make possible an optimal damping both for the 
decompression damping and the compression damping. 
To create not only a structurally simple damping valve, but also a 
structurally simple attachment of the pump rod, in an additional 
embodiment, the invention teaches that a pump rod, which pump rod is 
inserted in the pump cylinder, can be fixed in position by means of a 
retaining element, wherein the retaining element can be connected to the 
work cylinder and straddle the work cylinder. 
A satisfactory flow connection between the work cylinder and the high 
pressure chamber can essentially be ensured by providing the retaining 
element with recesses. 
A configuration of the valve seat which can be simple from a manufacturing 
point of view becomes possible if the valve seat is formed on the end 
surface of the work cylinder. 
To appropriately vary the damping forces, in an additional embodiment the 
valve plates can be biased by means of a bracing element. 
To achieve damping forces of different magnitudes as a function of the 
direction of flow, the invention teaches that in an additional embodiment, 
the valve seat and the second valve seat can each be realized for a single 
direction of flow. It is thereby advantageous that the valve plates each 
open in one direction and close the flow connection in the opposite 
direction. Such a capability can be achieved by corresponding stops for 
the valve plates. 
The above discussed embodiments of the present invention will be described 
further hereinbelow with reference to the accompanying figures. When the 
word "invention" is used in this specification, the word "invention" 
includes "inventions", that is, the plural of "invention". By stating 
"invention", the Applicants do not in any way admit that the present 
application does not include more than one patentably and non-obviously 
distinct invention, and maintains that this application may include more 
than one patentably and non-obviously distinct invention. The Applicants 
hereby assert that the disclosure of this application may include more 
than one invention, and, in the event that there is more than one 
invention, that these inventions may be patentable and non-obvious one 
with respect to the other.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The self-pumping hydropneumatic shock absorbing strut illustrated in FIGS. 
1 and 1b includes a work cylinder 3, which is divided into two work 
chambers 100; 101 by a piston 12 which is fastened to a piston rod 11. The 
work cylinder 3 is coaxially surrounded by a low pressure chamber 13 and a 
high pressure chamber 14. Gas and damping medium are introduced into the 
low pressure chamber 13, while the high pressure chamber 14 separates the 
damping medium from the gas volume by means of a membrane 15. Between the 
upper work chamber 100 of the work cylinder 13 and the high pressure 
chamber 14, a pump rod 5 is held by means of a retaining element 7, 
whereby the retaining element 7 simultaneously fixes the position of a 
valve 1, which valve includes a spring plate 2. The piston rod 11 is 
hollow, whereby the cavity therein represents a pump cylinder 8 into which 
the pump rod 5 can be inserted. 
As a result of the in and out movements of the piston rod 11, damping 
medium is transported from the low pressure chamber 13, via the pump rod 5 
in connection with the pump cylinder 8, into the high pressure chamber 14. 
The gas cushion on the reverse side of the membrane 15 is thereby 
compressed as a function of the load and acts as a gas spring. When the 
body of the vehicle has reached the specified level, the pumping process 
is neutralized, e.g. by means of a special shaping of the pump rod 5. The 
damping in the decompression and compression stage for the vehicle is 
accomplished by the valve 1. 
In accordance with one possible embodiment of the present invention (not 
shown), the pump rod 5 can be shaped such that the end of the pump rod 5 
which enters the pump cylinder 8 can be tapered so as to have a smaller 
diameter at that end. In another possible embodiment (not shown) the pump 
rod 5 can have a cut away section in the end entering the pump cylinder 8. 
The membrane 15 illustrated in FIG. 1 is a one-piece membrane, while in 
FIG. 1a, the retaining element 7 has been radially widened and encloses a 
ring-shaped membrane 15a. The membrane 15a illustrated in FIG. 1a is 
thereby provided on each end surface with a fastening bead which is used 
simultaneously to seal the gas chamber with respect to the high pressure 
chamber 14. Otherwise, the function of the shock absorbing strut 
illustrated in FIG. 1a is comparable to the action of the shock absorbing 
strut illustrated in FIG. 1. 
The internal level regulation of the shock absorbing strut can be 
accomplished with structure which can be included into the piston 12 and 
the work cylinder 3. An example of a structure which can be incorporated 
to accomplish this function can be seen in FIG. 1 of U.S. patent 
application Ser. No. 08/761,358, filed with the U.S. Patent and Trademark 
Office on or about Dec. 6, 1996, having the inventor Hubert Beck and 
having the attorney docket number NHL-FIS-236. 
FIG. 2 shows a detail of a valve 1, in which the work cylinder 3 carries 
the retaining element 7, whereby as shown in FIG. 3, the retaining element 
7 is provided on one hand with recesses 9 for the flow connection from the 
work chamber 100 into the high pressure chamber 14, and whereby a boring 
16 is used to locate the pump rod 5. FIG. 2 also shows that the valve 
plate 2 is enclosed radially inward between the end surface of the work 
cylinder 3 and the retaining element 7 on the one hand, and the pump rod 5 
and the retaining element 7, on the other hand. The end surface of the 
work cylinder 3 thereby forms a radially outer valve seat 4, while a 
second valve seat 6 is provided radially inward in the vicinity of the 
pump rod 5. 
The function of the compression stage is illustrated in FIG. 4, in which 
when the piston 12 is inserted, the spring plate 2 opens the valve seat 4 
radially outwardly, and makes possible a flow connection from the upper 
work chamber 100, past the valve seat 4, through the recesses 9 into the 
high pressure chamber 14. The valve seat 6 located radially inwardly is 
thereby correctly closed by the elevated internal pressure in the work 
chamber 100. 
In the decompression stage, on the other hand, i.e. when the piston 12 is 
being extended, the damping medium, as illustrated in FIG. 5, moves from 
the high pressure chamber 14 through the recesses 9, past the second valve 
seat 6 and into the work chamber 100. As a result of the corresponding 
pressure on the valve plate 2, the valve seat 4 is closed radially 
outwardly. The thickness, number and bias of the valve plate or plates 2 
are decisive in determining the level and characteristic of the damping 
force. As a result of the pressurization by the damping medium over a wide 
area, even sharply degressive characteristics can be achieved without 
problems. The ratio of decompression to compression damping is determined 
primarily by the inside and outside diameter of the valve plate 2. 
FIGS. 6 to 8 illustrate embodiments of valves 1 in which the shock 
absorbing strut is realized without a pump rod. In that case, the work 
cylinder 3 forms the valve seat 4 together with the valve plate 2, while 
the valve plate 2 radially inwardly forms the second valve seat 6a 
together with the retaining element 7. A bias can be applied to the valve 
plate 2 by means of a corresponding threaded connection 17. 
In FIG. 7, this bias can be applied to the valve plate 2 by means of a 
bracing element 10 and a corresponding threaded connection 17 between the 
bracing element 10 and the retaining element 7. 
FIG. 8 is largely similar to the embodiment illustrated in FIG. 7, with the 
distinction that the bracing element 10 can be fixed in place, after the 
application of an appropriate force P, by means of a laser weld 18. 
FIG. 9 also shows a shock absorbing strut which includes the work cylinder 
3, the pump rod 5 and the high pressure chamber 14, and is realized in the 
form of a shock absorbing strut which is used to guide the wheel. For this 
purpose, the retaining element 7 is extended radially outward so that the 
corresponding support forces between the work cylinder 3 and the outer 
tube 19 can be absorbed. In accordance with one embodiment, the retaining 
element 7 can extend radially outwardly up to the outer tube 19. 
FIG. 10 illustrates an alternative embodiment of a shock absorbing strut 
including a non-return valve 102 to allow damping medium to return to the 
low pressure chamber 13 upon depressurization of the shock absorbing 
strut. 
An alternative embodiment, illustrated in FIG. 11, includes a work cylinder 
213, a piston rod 212 and a piston 206, as well as a low pressure chamber 
201 and a high pressure chamber 204. The high pressure chamber 204 is 
divided by means of a ring-shaped separating piston 219 into a gas chamber 
220 and the chamber 204 which is filled with damping medium. Between the 
piston rod 212 and the work cylinder 213 is a pump chamber 203 which is 
connected to the low pressure chamber 201 by means of a regulating device 
207. There is also a non-return valve 202 which provides the flow 
connection between the low pressure chamber 201 and the pump chamber 203. 
There can also be a flow connection to the high pressure chamber 204 from 
the pump chamber 203 by means of a non-return valve 205. FIG. 11 shows the 
shock absorbing strut in the pumping-up or pressurization or compression 
phase, whereby the damping medium flows out of the low pressure chamber 
201 via the non-return valve 202 into the pump chamber 203. The high 
pressure chamber 204 which is under an initial gas pressure holds the 
non-return valve 205 in the closed position and pressurizes the surface of 
the piston 206. In the decompression stage, the non-return valve 202 
closes and the damping medium from the pump chamber 203 travels via the 
non-return valve 205 into the high pressure chamber 204. As a result of 
the in-and-out movements of the piston rod 212, the damping medium is 
continuously pumped from the low pressure chamber 201 into the high 
pressure chamber 204. 
In this embodiment, the regulating device 207 can include a resilient or 
flexible part 208 and a closing element 209, which keeps a recess or 
passage 211 of the work cylinder 213 closed by means of a seal element 
210. 
In the pumping-up phase illustrated in FIG. 11, the closing element 209, 
which closing element 209 is realized in the form of a permanent magnet is 
pressurized by the piston rod 212 and thereby closes the recess 211. The 
magnetic force of the permanent magnet can be selected so that the recess 
211 is opened above a specified pressure in the pump chamber 203. From 
this time forward, the damping medium from the pump chamber 203 is no 
longer pumped into the high pressure chamber 204, but directly into the 
low pressure chamber 201. The regulating device 207 also prevents the 
penetration of the gas in the low pressure chamber 201 into the pump 
chamber 203. 
In another possible embodiment, the regulating device 207 can be designed 
so that the regulating device 207 can unblock the passage 211 if the 
pressure in the pump chamber 203 exceeds a predetermined pressure. This 
can be done by limiting the magnetic field of the permanent magnet to a 
level that is only sufficient to hold the closing element 209 in the 
blocked position up to a certain pressure differential between the pump 
chamber 203 and the low pressure chamber 201. In the event the pressure 
differential between the low pressure chamber 201 and the pump chamber 203 
passes the predetermined threshold, the passage 211 can be unblocked and 
the damping medium can be allowed to flow from the pump chamber 203 into 
the low pressure chamber 201. 
FIG. 12 illustrates a possible embodiment of the shock absorbing strut, as 
depicted in FIG. 11, in the regulation phase. The piston rod 212, together 
with the piston 206, is below the recess 211, so that the permanent magnet 
of the regulating device 207 is no longer in the field of action of the 
piston rod 212. When there is a corresponding pressure in the high 
pressure chamber 204, the closing element 209 then opens and releases the 
recess 211, so that a corresponding pressure equalization can take place 
between the high pressure chamber 204 and the low pressure chamber 201. 
In a further embodiment of the present invention, there is a work chamber 
218, which is open to the high pressure chamber 204 which is aligned with 
the recess 211 when the piston 206 is below the recess 211. 
FIG. 13 illustrates yet another embodiment of a self pumping shock 
absorbing strut with internal level regulation for rotor vehicles which 
shock absorbing strut has a work cylinder 302 of the shock absorbing 
strut, in which a damping piston 306 on the end of a hollow piston rod 307 
slides. The work cylinder 302 is closed on the one side by a base and on 
the other side by a cover, through which the hollow piston rod 307 extends 
outward in a sealed manner. The shock absorbing strut is fastened to the 
body of a vehicle and to the axle of a vehicle in a manner not 
illustrated. The work cylinder 302 is surrounded by a ring-shaped low 
pressure chamber 308 which is filled partly with damping medium and partly 
with gas, and in the opposite area, the work cylinder 302 is surrounded by 
a high pressure chamber 309 which is divided by means of a membrane 310 
into an area 309a which is filled with damping medium and an area 309b 
which is filled with gas. 
In the completely depressurized state, i.e. when the shock absorbing strut 
is not pumped up, the same pressure prevails in the low pressure chamber 
308 and in the high pressure chamber 309. The work cylinder 302, by means 
of borings or passages 311 on the end surface 313, has a throttled and/or 
damped connection with the high pressure chamber 309. The damping piston 
306 is provided with non-return valves 312 to control the shock absorbing 
strut, whereby the work cylinder 302 is provided in its end surface 313 
with a pump rod 301 which consists of an inner part 303 and an outer part 
304. The pump rod 301 is guided through an opening of the damping piston 
306, and together with the cavity in the hollow piston rod 307 forms a 
pump. 
The shock-absorbing strut functions as follows. When the pump rod 301 is 
inserted into the hollow piston rod 307, the damping medium in the cavity 
of the piston rod 307 is transported on account of the non-return valve 
312 into the upper part of the work cylinder 302, and from there via the 
boring 311 pressurizes the gas cushion 309b in the high pressure chamber 
309. When the piston rod 307 is extended, damping medium once again flows, 
controlled by the non-return valve 312, out of the low pressure chamber 
308 via corresponding openings into the cavity of the hollow piston rod 
307. After reaching the desired level, any further pumping action is 
neutralized by the conical area 314 of the pump rod 301. The flow passage 
315 allows for return flow of damping medium from the work cylinder 302 to 
the low pressure chamber 308. 
One feature of the invention resides broadly in the self-pumping 
hydropneumatic shock absorbing strut with internal level regulation, in 
particular for motor vehicles, with a work cylinder which is filled with 
oil, is under the pressure of at least one gas cushion which is located in 
a corresponding at least one high pressure chamber and acts as a spring, 
which work cylinder is divided by a piston carried on a hollow piston rod 
into two work chambers, with a piston pump which is driven by the spring 
movements and transports oil from a low pressure chamber into the work 
chamber which is connected to the high pressure chamber, and the pump 
cylinder of the piston pump is formed by the hollow piston rod, whereby 
there are valves between the work chamber and the high pressure chamber 
for the decompression and compression damping, characterized by the fact 
that as a valve 1 there is at least one valve plate 2 which interacts with 
a valve seat 4 which is located on the work cylinder 3. 
Another feature of the invention resides broadly in the shock absorbing 
strut characterized by the fact that the valve plate 2 is supported 
radially inwardly on a second valve seat 6 which is located on a pump rod 
5. 
Yet another feature of the invention resides broadly in the shock absorbing 
strut characterized by the fact that the valve plate 2 is supported 
radially inwardly on a retaining element 7 which is connected to the work 
cylinder 3 and straddles or bridges the work cylinder 3. 
Still another feature of the invention resides broadly in the shock 
absorbing strut characterized by the fact that a pump rod 5 which is 
inserted into the pump cylinder 8 is fixed in position by means of a 
retaining element which is connected with the work cylinder 3 and 
straddles the work cylinder 3. 
A further feature of the invention resides broadly in the shock absorbing 
strut characterized by the fact that the retaining element 7 is provided 
with recesses 9. 
Another feature of the invention resides broadly in the shock absorbing 
strut characterized by the fact that the valve seat 4 is formed on the end 
surface of the work cylinder 3. 
Yet another feature of the invention resides broadly in the shock absorbing 
strut characterized by the fact that the valve plates 2 can be biased by 
means of a bracing element 10. 
Still another feature of the invention resides broadly in the shock 
absorbing strut characterized by the fact that the valve seat 4 and the 
second valve seat 6, 6a are each realized for a single direction of flow. 
The following U.S. patent applications: Ser. No. 08/761,358, attorney 
docket no. NHL-FIS-236, corresponding to Federal Republic of Germany 
Patent Application no. 195 45 661.0, having inventor Hubert Beck and filed 
in the Federal Republic of Germany on Dec. 7, 1995; Ser. No. 08/760,882, 
attorney docket no. NHL-FIS-237, corresponding to Federal Republic of 
Germany Patent Application no. 195 45 662.9-21, having inventor Hubert 
Beck and filed in the Federal Republic of Germany on Dec. 7, 1995; and 
Ser. No. 08/769,663, attorney docket no. NHL-FIS-235, corresponding to 
Federal Republic of Germany Patent Application no. 195 47 536.4, having 
the inventor Hubert Beck and filed in the Federal Republic of Germany on 
Dec. 20, 1995. 
All of the patents, patent applications and publications recited herein are 
hereby incorporated by reference as if set forth in their entirety herein. 
The corresponding foreign patent publication applications, namely, Federal 
Republic of Germany Patent Application No. 195 47 535.6-12, filed on Dec. 
20, 1995, having inventor Hubert Beck, and DE-OS 195 47 535.6-12 and DE-PS 
195 47 5535.6-12, are hereby incorporated by reference as if set forth in 
their entirety herein. 
Although only a few exemplary embodiments of this invention have been 
described in detail above, those skilled in the art will readily 
appreciate that many modifications are possible in the exemplary 
embodiments without materially departing from the novel teachings and 
advantages of this invention. Accordingly, all such modifications are 
intended to be included within the scope of this invention as defined in 
the following claims. 
The invention as described hereinabove in the context of the preferred 
embodiments is not to be taken as limited to all of the provided details 
thereof, since modifications and variations thereof may be made without 
departing from the spirit and scope of the invention.