Method of picking up and depositing a hollow receptacle such as a bin, container or the like by and on, respectively, a vehicle with change gear mechanism; change gear mechanism for carrying out the method; and receptacle designed for use in such method

For picking up and depositing a hollow receptacle such as a bin, container or the like by/on a vehicle with a change gear mechanism having a tilting frame pivoted in the back on the undercarriage of the vehicle and movable by a tilting cylinder supported on the undercarriage, and furthermore having a coulisse displaceable on the tilting frame by associated actuating elements and equipped with a stop element capable of being engaged with the associated fitting on the receptacle, the coulisse, for depositing the receptacle, is first retracted until the rear end of the receptacle projects beyond the back of the vehicle by a predetermined measure. Subsequently, the tilting frame is utilized until the lower zone on the rear end of the receptacle rests on the surface of the roadway. Thereafter, the actuating elements of the coulisse are switched to idle run, and subsequently, with the brakes of the vehicle released, if need be, the tilting frame is tilted further until the receptacle is standing upright on its rear end and the stop element and the fitting can be disengaged. For picking up the receptacle, the above operation takes place in the reversed sequence.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a method for picking up and depositing a hollow 
receptacle such as a bin, container or the like by and on, respectively, a 
vehicle equipped with a change gear mechanism having a tilting frame, 
which is pivoted at the back of the undercarriage of the vehicle and 
movable by means of a tilting cylinder supported on the undercarriage, and 
which has a coulisse displaceable on the tilting frame by means of 
associated actuating elements, such coulisse being equipped with a stop 
element capable of being engaged in the associated fitting on the 
receptacle. 
2. Prior Art 
Vehicles equipped with a change gear mechanism are special vehicles capable 
of picking up or depositing and transporting empty or filled change 
receptacles. In particular bins are placed in an upright or vertical 
position. However, they have to be transported in a lying position when 
moved with the vehicle to and from the location in which they are placed. 
Thus the pick-up and depositing of such bins requires change gear 
mechanisms capable of changing a receptacle to be set up, in particular a 
bin, from its lying position to the upright or vertical position. This 
operation requires special constructional measures enabling both the 
vehicle and the change gear mechanism to safely negotiate also the 
substantial weights of filled receptacles, in particular bins, while the 
latter are being picked up or deposited. For this reason, vehicles with 
change gear mechanisms are equipped especially within the zone in the back 
of the vehicle with supports capable of being extended or folded outwardly 
or made ready for operation in some other way, which supports, prior to 
the pick-up or depositing operation, are moved into a supporting position 
in which they support the vehicle on the ground or surface of the roadway. 
This entails the drawback that the supports signify a relatively high loss 
in payload and, furthermore, that the stability of the vehicle is 
problematic, for example in that a supporting leg may give way and sink 
into the ground under unfavorable ground conditions. 
Furthermore, picking up and depositing heavy receptacles, in particular 
bins, is made difficult by the fact that the operation of the change gear 
mechanism requires simultaneous controlling of the tilting motion of the 
tilting frame and of the displacement motion of the coulisse of the 
tilting frame. Such controls are carried out by hand, as each receptacle 
or bin needs to be operated or negotiated in a way adapted to its specific 
type of construction or its dimensions. This means that the safety in 
picking up and depositing receptacles, in particular bins, is highly 
dependent upon the care and skill of the person operating the change gear 
or the vehicle equipped with such change gear. 
SUMMARY OF THE INVENTION 
The invention is based on the problem of facilitating the pick-up and 
depositing of a receptacle, in particular a bin, by and on a vehicle 
equipped with a change gear mechanism. 
According to the invention, this problem is resolved by a method in which 
for the depositing of the receptacle, the coulisse is retracted until the 
rear end of the receptacle projects by a predetermined measure beyond the 
back of the vehicle, whereupon the tilting frame is slightly tilted until 
the lower part of the rear end of the receptacle rests on the surface of 
the roadway, the actuating elements of the coulisse are switched to idle 
motion, and the tilting frame is subsequently tilted further, if necessary 
with the brakes of the vehicle released, until the receptacle is standing 
upright on its rear end and the stop element and the fitting can be 
disengaged. 
In the method of the invention, the receptacle, in particular a bin which 
has been transported on the change gear mechanism of the vehicle in its 
lying position, is first pushed rearwardly into a certain position by 
controlled displacement of the coulisse, preferably to an extent such that 
after the tilting frame has been set to about 45.degree., the end of the 
receptacle, bin or container is forced against the ground. This causes the 
weight of the receptacle to be shifted to the rear end of the latter, and 
the receptacle is stabilized by resting on the surface of the roadway or 
ground, with the ensuing advantage that the payload of the vehicle is 
increased correspondingly. 
As soon as the receptacle has reached this partly supporting position, the 
actuating element of the coulisse is switched to idle run, with the 
significant advantage that the tilting frame can be steplessly tilted in 
this way in one continuous tilting operation until in the vertical line. 
During tilting into the vertical line, the coulisse remains connected with 
the bin, so that because of its idle run, it is capable of sliding out 
further, or it is extended automatically. As soon as the receptacle or the 
bin has been brought into the vertical position with the help of the 
tilting frame and is safely put into place in its location on the ground, 
the stop element can be released from the fitting of the container or bin. 
The operational sequence described above takes place in the reversed order 
for picking up an upright container: The vehicle drives close to the 
standing bin, swivels its tilting frame into the vertical line, and 
extends the coulisse of the tilting frame until the stop element can be 
engaged with the fitting of the bin. As soon as the stop element has 
engaged the fitting of the receptacle, the actuating element of the 
coulisse is again switched to idle run, and the pick-up operation can take 
its course while the tilting frame is tilting inwardly until the 
receptacle has reached again the approximately 45.degree.-position, 
whereupon it is finally placed on the vehicle. 
Both during pick-up and depositing operations, the receptacle or bin swivel 
around the points of support with which its rear end supports itself on 
the surface of the roadway or ground. This support position is reached, as 
described before, when the tilting frame is in a position of tilt of about 
45.degree.. However, said support position may have been reached or 
assumed also in positions of tilt greater or smaller than 45.degree.. 
Within the swivel range between the upright position and said position of 
about 45.degree., the brakes of the vehicle equipped with the change gear 
mechanism have to be released in order to permit the axis of swivel, 
around which the tilting frame is moving, to follow during its tilting 
motion the forced guidance in a circular path around the point of support 
of the bin on the ground, by having the vehicle performing a rolling 
motion on the surface of the roadway or ground. 
For picking up a standing container, the method of the invention is 
developed further with a special benefit in that following the engagement 
or locking of the stop element in the fitting of the container, the rear 
of the vehicle is lifted by a predetermined measure on the standing 
container. Such lifting of the rear part of the vehicle can be 
accomplished, for example by shortening the length of the tilting frame 
and retracting the coulisse into the tilting frame correspondingly, using 
its actuating elements. For example, the rear part of the vehicle may be 
lifted until the rear wheels of the vehicle are clear of the ground. This 
measure of lifting the rear part of the vehicle has the advantage that the 
weight of the vehicle is fully engaged as a counterweight via the tilting 
hydraulics, which means that even vehicles having a relatively light 
weight are capable of taking on an upright receptacle, in particular bins. 
After the rear part of the vehicle has been lifted, the tilting frame may 
be swivelled back until the wheels of the vehicle are in the same plane as 
the rear end of the bin, such plane being the surface of the roadway in 
the present case. Subsequently, the actuating elements operating the 
coulisse are again switched to idle run until the receptacle, in 
particular the bin has been picked up by the vehicle. 
The method of the invention for picking up and depositing receptacles, in 
particular bins, has the additional advantage that it permits exact 
placement or positioning of bins or containers having draining or filling 
openings on a face side on which they are required to stand, which means 
such containers or bins have to be positioned exactly on the matching 
openings or outlets in the ground. Such precise set-up is made possible on 
account of the fact that at its end side, the container can already be 
engaged or locked in adapters or similar guiding devices before it is 
placed in its final position. This is made possible through the rolling 
motion of the vehicle in that during the tilting motion, final 
adjustments, if required, are automatically effected by such motion. 
Of course, the method of the invention, in which actuating elements for a 
coulisse changing the length of the tilting frame are switched to idle 
run, may be used also with change gear mechanisms in which the coulisse is 
replaced by ropes, chains or similar pulling means, which are capable of 
being engaged on the change container and capable of moving the latter 
along the tilting frame. However, change gear of the type here under 
discussion is equipped with hydraulics in most cases. 
Change gear mechanisms are known in which the coulisse is designed with the 
shape of an "L", whereby one leg of the "L" is guided moving back and 
forth in the tilting frame, and the freely projecting leg of the "L" is 
equipped with a stop element, which is a hook in most cases. Such hook may 
be engaged in fittings arranged on the face side of change containers to 
be picked up, in order to pick up and deposit such change containers. 
A particularly advantageous embodiment of a change gear mechanism for 
carrying out the method according to the invention, for which embodiment 
independent protection is claimed, is characterized in that the coulisse 
is embodied in the form of a simple sliding frame of which the free end 
has the stop element. Thus the L-shaped coulisse is missing in such a 
change mechanism. Consequently such change gear has a significantly lower 
weight, resulting in a further increase of the payload. With particular 
benefits, such a change gear mechanism is suitable also for vehicles 
equipped with a press, into which bulk material such as, for example, 
household refuse to be collected, can be loaded. The compressed material 
so collected is then discharged by the press into a receptacle also picked 
up by the vehicle by means of a change gear. As soon as the receptacle has 
been filled, it may be deposited with the change gear, and the vehicle can 
pick up a new, empty change receptacle. 
With such vehicles, the press is mounted directly behind the driver's 
cabin, with the outlet of the press projecting into the receptacle, which 
is placed directly against the press and supported on the vehicle equipped 
with the change gear mechanism. With the change gear mechanism according 
to the invention, in which the coulisse is designed as a single sliding 
frame by which the tilting frame can be lengthened or shortened, the 
advantageous method of picking up and depositing receptacles thus is 
applicable also with vehicles equipped with a compactor or press. 
Advantageously, the change gear mechanism has a low weight, but it is 
nevertheless capable of picking up and depositing even heavy receptacles 
in a safe and trouble-free way as described before. 
With the change gear mechanism according to the invention, the actuating 
element for the coulisse is at least one operating cylinder, for example a 
double-action operating cylinder. In order to switch the actuating element 
to idle run, provision is made for an operating arrangement by which such 
an operating cylinder can be brought into a floating position, which can 
be accomplished, for example by installing a bypass in the pressure fluid 
conduits of the operating cylinder for the displacement of the coulisse, 
such bypass being capable of being operated by means of operating shutoff 
elements. 
Furthermore, the change gear mechanism is characterized in that the stop 
element has a locking element capable of being actuated. Such locking 
element permits maintaining the mutual engagement between the stop element 
of the coulisse and the fitting of the container or receptacle even while 
the coulisse is being retracted, in order to lift the rear part of the 
vehicle on a standing receptacle to be picked up. 
By way of example, the locking element may be a simple locking bolt capable 
of being actuated by hand or pneumatically or hydraulically or in some 
other way, and designed to lock the jaws of a stop element designed in the 
form of a hook. 
Any lateral displacement or shifting of the receptacle has to be avoided 
particularly during the transport of the receptacle lying on the vehicle. 
According to another beneficial feature of the invention, such securing of 
the receptacle is realized with the change gear mechanism of the invention 
in that the tilting frame has guide elements disposed within its lateral 
zone and engaging guide elements on the receptacle. 
So as to avoid adjustments of the receptacle and the tilting frame in order 
to engage the guide elements on the tilting frame and receptacle with one 
another, which may be troublesome, provision is made that the guide 
elements on the tilting frame are capable of swinging or folding into and 
from the engaging position. It is particularly advantageous that each 
guide element is embodied in the form of a folding roller supported on the 
tilting frame, such folding roller having a rolling body projecting into a 
guide rail of the receptacle and being equipped with a radially projecting 
rim in order to perform lateral guiding functions also on the outside of 
the guide rail.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 shows a vehicle 1 with a driver's cabin 2 and the undercarriage 3. A 
tilting frame 5 is pivoted on the undercarriage in the back of the vehicle 
within the zone of the back 4 of the vehicle. The tilting frame is 
pivotable around the axis 6 indicated in this figure. In the pivot point 7 
on the undercarriage, a tilting cylinder 8 is supported, which engages the 
tilting frame 5 at point 9. When the piston of the tilting cylinder 8 is 
extended, the tilting frame 5 is pivoted around the axis 6 and driven into 
predetermined positions of tilt. The free front end of the tilting frame 5 
is designed as a guide for a coulisse 10, which, by means of an actuating 
element--for example an operating cylinder not shown in the drawing--, can 
be extended from the tilting frame in order to extend such frame, or 
retracted into the frame in order to shorten the latter. 
A receptacle 11, which is a bin in the present case, lies or rests on the 
tilting frame 5 and its coulisse 10. The bin has a fitting 12, by means of 
which it is engaged in a stop element 13 on the free end of the coulisse 
10. When the coulisse is extended or retracted relative to the tilting 
frame 5, the bin 11 can be pulled on the vehicle towards the driver's 
cabin 2, or, if the tilting frame is shortened by retraction of the 
coulisse 10, pushed or displaced rearwardly beyond the back 4 of the 
vehicle until the supporting legs at the rear end 15 of the bin, which 
hold the bottom 14--which is fitted with an outlet--of the bin at a 
certain level above the set-up surface of the bin, project by a 
predetermined measure beyond the back of the vehicle. Such a position is 
shown in FIG. 1a. In this position, the total weight of the bin has been 
shifted in the direction of the rear axle of the vehicle. 
According to FIG. 1b, the tilting cylinder 8 is extended in a next step of 
the operation, so that the bottom rear end 15 of the bin comes to rest on 
the ground as shown in the figure, such ground being the roadway surface 
16 in the present case. While in this position of tilt of about 
45.degree., the point of gravity of the bin, and thus its total weight, is 
still disposed approximately above the rear axle of the vehicle, so that 
the points of support of the slightly tilted bin on the surface of the 
road and the rear wheels of the vehicle form a multi-point support for the 
partly tilted bin, which, therefore, is relatively stable and safely 
supported in this position. 
For tilting the tilting frame further until the bin is in its vertical 
position, the actuating element of the coulisse, which is a double-action 
working cylinder in the present case, is switched to the idle-run 
position, which can be accomplished with the cylinder by means of suitable 
bypasses in the pressure medium feed conduits. The working cylinder moving 
the coulisse is displaced in this way into a so-called "floating 
position", which permits the coulisse to move freely while the tilting 
cylinder 8 is moving the tilting frame and thus also the bin from the 
45.degree.-position according to FIG. 1b into the upright or vertical 
position according to FIG. 1c, in which process of motion the tilting 
frame and the bin are continuously passing through the various positions 
of tilt indicated in FIG. 1c. At the same time, the bin swivels around an 
axis disposed in the plane of the surface of the roadway. The axis 6, 
around which the tilting frame pivots in relation to the undercarriage, is 
able to follow such motion if the brakes of the vehicle are released, 
because as the bin is being erected or set up straight, the vehicle rolls 
back and approaches the point of support of the bin on the surface of the 
road. 
When a bin is picked up, the above sequence of steps takes place in the 
reverse order: The vehicle is driven close to the standing bin. Then the 
tilting frame is driven into a vertical position until it rests against 
the standing bin and its stop element has engaged the fitting 12 of the 
bin. This position corresponds with the vertical position of the bin in 
FIG. 1c. 
By shortening the vertically extending tilting frame, which, for example, 
can be accomplished by retracting the coulisse 10 into the tilting frame, 
the back 4 of the vehicle is lifted on the bin 11 until the wheels 17 of 
the vehicle have more or less cleared the surface 16 of the roadway as 
shown in FIG. 1d. In the latter figure, the tilting cylinder 8, which is a 
multi-stage cylinder in the present case, is extended. For picking up the 
bin 11, the tilting cylinder is retracted until the rear wheels 17 of the 
vehicle touch again the ground. During this tilting movement, the weight 
of the vehicle serves as a counterweight for tilting the bin 11. This 
permits picking up even filled and, therefore, relatively heavy bins 11 
with relatively light vehicles without any problem. 
The following phases of the pick-up operation take place in the reversed 
sequence of the operation described above, until the bin rests again on 
the vehicle as shown in FIG. 1. 
FIG. 2 shows a vehicle with a bin 11 picked up on such vehicle. The change 
gear mechanism of the vehicle again consists of a tilting frame according 
to FIG. 1, and a coulisse extending or shortening the tilting frame; 
however, in the present case, the coulisse is embodied in the form of an 
L-shaped arm, of which the one leg 18 of the "L"-shaped element is 
retractably and extendably guided in the tilting frame, whereas the other 
leg 19 of the L-shaped element, which leg extends approximately vertically 
relative to the former, has a stop element disposed at its free end, 
which, in the present case, is a hook 20 adapted to engage a matching 
fitting on the face side 21 of the bin. For the purpose of reinforcing the 
support of the bin 11, an additional stop element approximately designed 
as shown in FIG. 3 may be arranged on the L-leg 18, which additional 
element is adapted to engage a fitting mounted on the side of the bin. 
With a change gear of this type, the pick-up and deposit operations can be 
carried out in the same manner as shown in FIGS. 1 to 1d. 
So that the back of the vehicle can be lifted on the bin in the manner 
specified above, a special embodiment of the stop element 13 engaging the 
fitting 12 of the bin to be picked up is required. A possible embodiment 
for a suitable stop element 13 is shown in FIG. 3, which illustrates a 
schematic lateral view of the top part of a bin 11 engaged in the change 
gear mechanism. The stop element 13 is comprised of a hook 13' projecting 
from the coulisse 10 and adapted to seize with the jaws of the hook a 
fitting 12 embodied in the form of a bolt. A locking element, which can be 
actuated, is arranged on the coulisse embodied in the form of a pivoting 
bolt 13" locking the jaws of the hook. This pivoting bolt can be operated 
electromagnetically, pneumatically or hydraulically. 
FIG. 4 shows a schematic lateral view of a vehicle for the collection of, 
for example household refuse. On its front side, which is equipped with 
the driver's cabin, the vehicle has a loading device 22, which is known 
per se. A compactor 23 is mounted behind the driver's cabin, but only 
indicated in the present figure. The material picked up with the loading 
device 22 can be charged in the feed shaft 24 of the compactor, which 
conveys the compacted material in the direction of the arrow 25 into a bin 
11' loaded on the vehicle. This bin or receptacle is provided with a 
matching opening disposed on the face side facing the compactor, through 
which opening the discharge mouth of the compactor projects into the bin. 
The vehicle is equipped with a change gear mechanism for picking up and 
depositing the bin 11'; only the tilting cylinder 8 of such mechanism is 
indicated in the present figure. The retractable and extendable coulisse 
of the tilting frame has the advantage that the bin 11, which is still on 
the vehicle, may be pulled off rearwardly from the mouth of the compactor 
as soon as it is to be deposited, or an empty bin, which has just been 
picked up, can be displaced forwardly against the compactor as shown by 
the double arrow 26. 
For depositing the bin, the tilting cylinder 8 is extended (FIG. 5), and 
the depositing operation takes place as described above. The filled bin 
can be deposited standing on a face side, and stored in that position 
until further transport, in the manner shown in FIG. 6. Of course, 
standing containers can be picked up as well, in which case the pivoting 
motion of the tilting frame is reversed. The pick-up and depositing 
operations are indicated in FIG. 6 by the double arrow 27. 
FIG. 7 shows a schematic lateral view of the back of the vehicle. In the 
present case, a bin-type container 11, which is indicated only in the 
fixture, rests on the tilted frame 5. On its side facing the tilting 
frame, this bin 11 is equipped with the guide elements 29, of which each 
element is a profiled rail, for example a U- or I-profile, which is 
arranged on the bin in a way such that the bin rests on the tilting frame 
with two parallel profiled rails. 
The guide elements 28 engaging the guide elements 29 are arranged on the 
tilting frame. Each guide element 28 comprises a folding roller 30 
supported on the free end of a folding lever 31. The latter is pivoted on 
the tilting frame 5. The foldability of the folding roller permits 
selectively engaging or disengaging the guide means 28 with or from the 
guide elements 29 of the bin 11. 
FIG. 8 shows a sectional view of a guide element, which is an I-profile in 
the present case, which is engaged by a guide means 28 embodied in the 
form of a folding roller 30. The foldability is indicated by the double 
arrow 31. FIG. 8 shows that each folding roller 30 consists of a rolling 
body 32 capable of engaging between the T-flanges of the I-profile and 
rolling off on a reinforcing rail 33 of the bottom T-flange 34. Each 
rolling body has a projecting rim 35 for the purpose of lateral guidance. 
The two piston cylinders numbered 8 and 8a in FIG. 9 correspond to the 
working cylinders numbered 8 in FIG. 1b of the present patent application. 
Cylinder 48 of FIG. 9 serves to move the coulisse 10 which is shown in the 
drawing, for example in FIG. 1b. 
The function of the floating switch is discussed in connection with FIG. 9, 
wherein means 41 is a directional control valve with manual operation; 
means 42 is a directional control valve with manual operation; means 43 is 
a directional control valve with manual operation; means 44 is a fluid 
power motor; means 45 is a storage chamber; means 46 is a check valve; 
means 47 is a OR-valve; means 48 is a sliding cylinder on the device for 
setting the container upright; and means 8 and means 8a are a pair of 
tilting cylinders for the swinging of the tilting frame 5. 
For garbage collection vehicles the process of picking up and setting down 
a container is facilitated by the fact that the container is initially 
located over the rear of the vehicle on the tilting frame by a 
pre-determined amount. The tilting frame is subsequently tilted through 
the operation of a first pressure medium piston cylinder unit until the 
lower area of the back end of the container rests on the roadway surface 
or on the ground. The second pressure medium piston cylinder unit moving 
the container on the auxiliary frame is then switched to the floating 
position so that the tilting frame can be tilted to a vertical position 
without alternating operation of the first and second pressure medium 
piston cylinder units after which it then stands upright on its bottom 
end. During the tilting into the vertical position, the second pressure 
medium piston cylinder unit can be extended and retracted in the required 
manner. 
In order to vertically set down a container from its initial horizontal 
position on a garbage collection vehicle reference is made to the fluid 
flow circuitry diagram of FIG. 9. Here the pressure medium piston cylinder 
unit 48 is initially retracted through the operation of the valve 43, 
switching position 43c. The retracting piston rod moves the container 
backwards by means of a hook and eyelet on the horizontal tilting frame 
towards the rear of the vehicle. Through the pressure lines 51 and 52 and 
also through the OR-valve 47 and the line 53 the pressure medium reaches 
the check valve 46. It is unlocked through the built up pressure and 
thereby enables the expelled pressure medium to flow back into the storage 
chamber 45 from the piston side of the pressure medium piston cylinder 
unit 48. With the help of check valve 46, a controllable rate for the 
setting down of the container is provided. Should the container slide 
during the process of swinging the tilting frame, this sliding could be 
avoided by switching valve 42 back to position 42a. 
When the container reaches its final position in which the rear end of the 
container sticks out over the rear of the vehicle, valve 43 is switched 
back to its position 43b. Through operation of valve 41, namely position 
41c the pressure medium piston cylinder units 8 and 8a extend and swing 
the tilting frame with the container. When the rear container edge touches 
the roadway surface, valve 41 is switched back to its position 41b. 
Subsequently, valve 42 is switched to position 42b which adds pressure to 
check valve 46 through line 54, the OR-valve 47, and line 53. Now the 
pressure medium piston cylinder unit 48 is switched to the floating 
position so that the pressure medium can be expelled by the piston on the 
piston side or on the piston rod side. 
Now the process of setting the container upright can continue by switching 
valve 41 to position 41c and further extension of the pressure medium 
piston cylinder units. Through the floating switch the container can 
slowly glide upwardly during the swinging of the tilting frame so that a 
faulty grip between the container and the tilting frame is avoided. 
Picking up a vertical container occurs in such a manner that initially the 
tilting frame is moved to a vertical position and by extending the second 
pressure medium piston cylinder unit 48 is order to allow the hook 
connected hereto to move into the container eyelet. Following this the 
hook and container eyelet are locked; and valve 42 is switched to position 
42b. In this manner it is possible that because of the floating switch the 
container can slide downwards on the tilting frame on the container edge 
standing on the ground when retracting the pressure medium piston cylinder 
units 8 and 8a in order to thus prevent faulty gripping. If the container 
edge is lifted off the ground, the floating switch is cancelled through 
setting valve 42 to position 42a. The tilting frame is completely swung 
down through retraction of the pressure medium piston cylinder units 8 and 
8a. Following this, the container is pushed to its final position on the 
vehicle through extension of the pressure medium piston cylinder unit 48.