Rodless pressure cylinder

A rodless pressure cylinder (1) has a cylinder housing (2) with a longitudinal slot (6) through it and is closed on each end by a cylinder cap (12). The longitudinal slot (6) is sealed on its inside by an inner sealing strip (7) and as necessary is also covered on its outside by an outer sealing strip (8). The provided sealing strips (7,8) are fastened by special clamping elements (11), in or on the longitudinal slot (6). The cylinder caps (12) are provided on each side with connectors for the feed and discharge of pressure medium. Since the sealing strips (7,8) are fastened by the special clamping elements (11) independent of the caps (12), the cylinder caps (12) can be installed in various positions on the cylinder housing (2). They are constructed rotationally symmetrical for this purpose, which is particularly valid for the pressure medium channels in the interior of the cylinder caps (12). The cylinder caps (12) can therefore be mounted on the pressure cylinder (1), respectively such that the respective connector (17) for the pressure medium lies in a sufficiently accessible position of the mounted pressure cylinder (1).

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention pertains to a rodless pressure cylinder with a cylinder 
housing which is provided with a longitudinal slot extending along its 
entire length and which has a cylindrical interior in which a 
longitudinally movable drive piston is arranged. A lateral attachment 
extends from this piston outwardly through the longitudinal slot. Cylinder 
caps are provided at the ends of the cylinder housing for enclosing the 
cylindrical interior thereof and a coupling is provided on the outside for 
the feed and discharge of the pressure medium which actuates the drive 
piston. The longitudinal slot is sealed by an interior sealing strip in 
the interior of the cylinder housing, which is lifted from the 
longitudinal slot only in the region of the attachment and penetrates 
through a guide channel in the drive piston. The slot is always sealed 
from the outside with an additional outer sealing strip which is fastened 
onto the outside of the cylinder housing over the longitudinal slot at its 
ends with clamping elements separated from the cylinder caps. 
2. The Prior Art 
A rodless pressure cylinder of the foregoing type of construction is 
disclosed in U.S. Pat. No. 5,245,910. The outer sealing strip which covers 
the longitudinal slot on the outside of the cylinder housing is anchored 
on both sides in this known apparatus by clamping elements separated from 
the cylinder caps on each side, the clamping elements being fastened onto 
the cylinder housing with two screws and each including a threaded hole 
for the connection of a pressure line. The threaded hole leads to the gap 
between the outer and inner sealing strips which extend up to the caps 
where a sealing is established between the clamping element holding the 
outer sealing strip and the inner sealing strip on the longitudinal slot. 
The longitudinal slot is thus sealed so that it is possible to produce a 
vacuum in the gap between the two sealing strips or an overpressure 
against the ambient pressure surrounding the pressure cylinder. In this 
way a leaking of pressure out of the pressure cylinder into the 
surrounding space or from the surrounding space into the cylinder is 
avoided, for example if the pressure cylinder is used in a pure or in an 
aggressive atmosphere. The fastening of the ends of the inner sealing 
strip is not described in this patent. Since the inner sealing strip is, 
however, exposed to a tensile load in its longitudinal direction during 
the operation of the pressure cylinder and the interior as well as the gap 
between the two sealing strips must be sealed, it must extend up to the 
two cylinder caps and be anchored to the cylinder housing with an elastic 
seal in form-locked fashion and not merely tensionally. It must therefore 
be presumed that the inner sealing strip is fastened to the cylinder 
housing in a conventional fashion by the cylinder cap. 
Pressure cylinders, pneumatic or also hydraulic cylinders, require air 
attachments for the feed of the pressure medium actuating the working 
piston of the cylinder, such attachments being enabled by means of threads 
of various sizes for the incorporation of screwed hose couplings or also 
of so-called plug connectors. The connectors lie in general 
perpendicularly to the axis of the pressure cylinder extending 
horizontally between the enclosure caps of the cylinder. During use of the 
pressure cylinder it is often required to have the connectors feed towards 
the other side or towards the bottom, perhaps also upwardly, since the 
placement relationship requires this during mounting of the pressure 
cylinder. 
In rod-piston cylinders having the driving force centered along the piston 
shaft, the prior position of the attachment on the pressure cylinder at 
production is not important since the cylinder is built rotationally 
symmetrical and a user is in a position to locate the attachment during 
mounting of the pressure cylinder by turning it about its axis to wherever 
he pleases. However, the construction forms of known cylinders with no 
drive rod known make the simple rotation of the cylinder impossible, since 
the force output does not result centrally at the end of the cylinder, but 
rather laterally on the cylinder through the longitudinal slot. The 
spatial positioning of the pressure cylinder is therefore determined by 
the position of the connectors for driving the equipment to be driven. 
Up until now, this problem has been solved in that for each rodless 
pressure cylinder, various cylinder caps have been offered with connectors 
lying at various positions. Another solution of the problem consists of a 
so-called universal cap, which has three equal threaded connectors. The 
unused connectors must be closed by means of plugs. 
The object of improving the known rodless cylinder of the type described 
above such that the connectors for the feed and discharge of the pressure 
medium can be provided off of the cylinder caps on desired sides of the 
cylinder in a simple way and without changing the caps establishes the 
basis of this invention. 
SUMMARY OF THE INVENTION 
The invention provides the means of attaining this object in that the inner 
seal strip is also anchored at each of its ends with a clamping element 
separated from the cylinder caps in or on the longitudinal slot and the 
two cylinder caps can be fastened onto the cylinder housing in various 
positions across from one another in the plane of the cylinder cap, and 
that the channels in the two cylinder caps transferring the pressure 
medium are constructed rotationally symmetrically in the transfer region 
between the cylinder cap and the neighboring component of the cylinder 
housing. The invention is really quite simple; however, it has not been 
recognized by practitioners since the cylinder caps in rodless cylinders, 
contrary to the pressure cylinders with drive pistons, are not built with 
rotational symmetry. As is commonly known, the seal strips sealing the 
inside of the longitudinal slot are clamped solid and fastened by means of 
the cylinder cap in the slot region with rodless cylinders. On this basis, 
a permanent positioning of the cylinder cap in relation to the cylinder 
housing is prescribed, so that a simple turning of the cylinder cap to 
another position seemed impossible. The separation of the fastening of the 
inner seal strip from the cylinder caps, first suggested by this 
invention, creates the fundamental prerequisite to enable these caps to be 
positioned in other positions by rotation. To accomplish this, it is 
necessary that all pressure medium channels and holes in the caps be 
arranged rotationally symmetric in order to ensure the required line 
connections in all possible installation positions. The invention makes it 
possible in any case to be able to choose separately the position of the 
connector for the feed and discharge of the pressure medium actuating the 
cylinder for each cylinder cap, so that the connectors can be laid out in 
a simple way in a location which is always sufficiently accessible for the 
installation as well as advantageous for the subsequent operation of the 
cylinder. 
The clamping elements with which the sealing strips are fastened on or in 
the longitudinal slot of the cylinder housing can be installed in the 
vicinity of the end of the cylinder housing in the longitudinal slot and 
be held to the walls of the longitudinal slot using an expanding setscrew 
with a wedging effect. The inside seal strip, which seals the longitudinal 
slot in the region of the cylinder space subject to pressure, can 
therefore be fastened to the clamping element form-locked while an outer 
sealing strip which seals the longitudinal slot from the outside can be 
tensionally locked to the clamping element. These clamping elements lie in 
a relatively narrow dead zone directly at the end of the cylinder housing. 
It is in this same zone in which the airtight sealing of the cylinder 
housing results. Each clamping element presses against the walls of the 
longitudinal slot by means of a wedging effect and effects a guaranteed 
anchoring of the inner as well as the outer sealing strip. Since the 
clamping element is axially displaceable in the longitudinal slot, the 
strip tension can be simply adjusted to the respective requirements. 
In a preferred embodiment of the invention, the cylinder cap, constructed 
preferably with multi-sided, for example rectangular or square, cross 
section, can be pressed onto the cylinder housing by hold-down bolts 
arranged symmetric to the center running parallel to the axis of the 
cylinder housing. In this embodiment, it is possible in a simple way to 
rotate the two cylinder caps after loosening of the hold-down bolts at an 
angle of 90.degree. in its plane so that the connector for the pressure 
medium can be provided in four different spatial positions. This 
embodiment has the added advantage that it requires no substantial changes 
of the previous construction of the rodless cylinder. 
In another variation of the cylinder according to the invention, the 
cylinder cap can be freely rotated on a cylinder surface centralized to 
the cylinder housing and coaxial to the cylinder surface. It is then 
possible to install the two cylinder caps with the connectors for the 
pressure medium in any desired spatial position. A further development of 
this embodiment provides that the cylinder caps are fastened to the 
cylinder housing by a carriage gripping them and which rotates relative to 
them. Hold-down bolts grip the carriage which press the cylinder caps onto 
the cylinder housing. 
In a further refinement of the invention, this can be used in a beneficial 
way as well in a rodless pressure cylinder which is provided with an 
end-position dampening for the drive piston. The end-position dampening 
consists, similarly to known embodiments, of dampening taps on the ends of 
the cylinder housing extending into it in the axial direction with a 
central channel for the feed and discharge of the pressure medium. The 
dampening taps work together with dampening cylinders on the sides of the 
drive piston. The central channel is closed off during penetration of a 
dampening tap and at least one dampening channel is provided lateral to 
each dampening tap which opens to the pressure medium connection through a 
throttle adjustable with a dampening screw. 
According to the invention, in a pressure cylinder with end-position 
dampening, the dampening screw for the adjustment of the throttle is 
arranged on the same side of the cap as the pressure medium connector, and 
is direct&d with its axis approximately in the same direction as the 
pressure medium connector. A connecting channel extending rotationally 
symmetrically in the cylinder cap is arranged between the dampening 
channel and the throttle. In this embodiment of the pressure medium 
cylinder, the dampening screw is also placed in the same location with the 
connector for the feed and discharge of the pressure medium so that the 
dampening screw lies at a position for good access and simple dampening 
adjustment. 
Further features and advantages of the invention will be understood by 
reference to the attached drawings taken in conjunction with the following 
description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In all embodiments of the invention the pressure cylinder 1 consists of a 
cylinder housing 2 which has a cylindrical interior 3 in which a drive 
piston 4 is moveable. The drive piston 4 is sealed in the cylindrical 
interior 3 with gaskets 5 on its ends and divides this interior into two 
independent (unconnected) pressure spaces on both sides of the drive 
piston 4. 
The cylinder housing 2 is provided with a longitudinal slot 6 passing 
therethrough over its entire length. This is sealed in the region of the 
two pressure spaces of the cylindrical interior 3 with sealing strips, 
i.e., by means of an inner sealing strip 7 and an outer sealing strip 8, 
which essentially seals the longitudinal slot 6 from the outside. A 
lateral attachment 9 is fastened to the drive piston 4 according to FIG. 
1, which leads through the longitudinal slot 6 out of the cylinder housing 
2, and in the embodiment of FIG. 1 terminates with an attachment flange 
10. The driving force of the pressure medium cylinder 1 is received by 
this attachment flange 10 and, via coupling of the attachment flange with 
a machine part to be driven by the pressure cylinder 1, is conveyed to the 
machine part. 
As is seen from FIG. 1, the two sealing strips, i.e., the inner sealing 
strip 7 and the outer sealing strip 8, are fastened at each end of the 
cylinder housing 2 with clamping elements 11 on or in the longitudinal 
slot 6. The clamping elements 11 are positioned immediately at the edge of 
cylinder caps 12, which are seal-pressed onto the cylinder housing 2 with 
four hold-down bolts 13. A dampening tap 14 extends from each cylinder cap 
12 towards the drive piston 4 in the cylindrical interior 3 of the 
cylinder housing 2. A dampening cylinder 15 is provided in each of the two 
ends of the drive piston 4, which both work together with the dampening 
taps 14. These are made hollow and are connected by a central channel 16 
with the respective connector 17 for the pressure medium driving the drive 
piston 4. Dampening screws 18 are installed laterally next to the 
connectors 17 in the two caps 12, which serve to adjust the throttling of 
a dampening apparatus for end-position dampening. 
It can be seen from FIG. 1 that the two cylindrical interiors 3 of the 
cylinder housing 2 between the respective cylinder cap 12 and the gasket 5 
of the drive piston 4 are sealed by the inner sealing strip 7. In the 
region of the radial attachment 9 of the drive piston 4, the inner sealing 
strip 7 penetrates a guide channel 19 and the outer sealing strip 8 is fed 
through a guide channel 20 equally provided in the radial attachment 9. 
The respective tension of the two sealing strips 7 and 8 can be regulated 
by the clamping elements 11 at their ends, which can be correspondingly 
displaced in the longitudinal slot 
As is seen in FIG. 2, the clamping elements 11 lie essentially in a dead 
zone between the end of the cylinder housing 2 and a gasket 21, from the 
standpoint of pressure impingement. The gasket is provided on a 
cylindrical attachment 22 which extends in from the cap 12 into the 
cylindrical interior 3. The essential construction of the clamping 
elements 11 is seen in FIGS. 3 and 3a. Each of these consist according to 
FIG. 3 of a housing 23 and a clamping key 24 which is drawn into a notched 
recess of the housing 23 by means of a clamping screw 25 and which spreads 
the housing and fastens it against the side walls of the longitudinal slot 
6. In the embodiment according to FIGS. 2a and 3a, the housing 23 of each 
clamping element 11 is fastened by means of a clamping screw 25 and a nut 
25a into the longitudinal slot 6. 
In both embodiments the interior sealing strip 7 extends up to the ends of 
the cylinder housing 2 and is held form-locked according to FIGS. 2 and 3 
by the bolt of the clamping screw 25, through an opening in the sealing 
strip. In the embodiment of FIGS. 2a and 3a, the ends of the inner sealing 
strip are clamped against the longitudinal slot 6 additionally with the 
nut 25a of the clamping screw 25. The outer sealing strip 8 is somewhat 
shorter in all examples than the inner sealing strip 7 and is held in 
place by a special holding arrangement 11a on the clamping element 11 or 
between this and the cylinder housing 2. 
The principle construction of the previous dampening apparatus can be seen 
in FIG. 4. Here, also, the cylinder housing 2 is closed with caps 12 
containing hold-down bolts, not shown, on its ends. An attachment 22 joins 
with the illustrated cap 12, in this case separate from the cap 12, which 
extends into the cylindrical interior 3 and seals it with gasket 21. A 
dampening tap 14 extends from the attachment 22, which works together with 
a dampening cylinder of the drive piston, both not shown. As in the other 
examples, the dampening taps 14 have a central channel 16, which is in 
communication with the connector 17. Parallel to the central channel 16 of 
the dampening tap, a dampening channel 26 penetrates the attachment 22 and 
connects the cylindrical interior 3 with a connecting channel 27 in the 
cap 12. This connecting channel 27 extends in the cap 12 rotationally 
symmetrically and leads to a throttle 29 through a connecting hole 28 
provided in the cap 12, which can be adjusted by means of the dampening 
screw 18. The throttle 29 is tied to the connector 17. 
With the use of the schematic representation in FIG. 5, the means of 
functioning of the invention can be illustrated. The cap 12 represented in 
FIG. 5 is constructed as a square and attached to the cylinder housing 2 
with the help of four parallel hold-down bolts 13, arranged symmetrically 
with respect to the center (only schematically depicted). The connector 17 
for the feed and discharge of the pressure medium activating the pressure 
cylinder 1 and the dampening screw 18 for the end-position dampening is 
located on the illustrated front side of the cap 12. The longitudinal slot 
6 lies above and in the middle of the cylinder housing 2, where the 
connecting flange 10 for the force transfer to the apparatus to be driven 
is also provided. The position of the connecting flange 10 and thus also 
the cylinder housing 2 is prescribed by this force transfer attachment. 
In order to shift the pressure medium connector 17, it is merely necessary 
to loosen the four screws 13, remove the cap 12 from the cylinder housing 
2, and, for example, to turn 90.degree. in the direction of the arrow 30 
or in the opposite direction, again insert the four hold-down screws 13 
and fasten it again with their help to the cylinder housing 2. If the cap 
12 is turned 90.degree. in the direction of the arrow 30, the connector 17 
and the dampening screw 18 are located on the top side of the pressure 
cylinder 1. With a rotation of 180.degree., the connector 17 and the 
dampening screw 18 lie on the (hidden) backside of the pressure cylinder 
1. By a 90.degree. rotation of the cap 12 opposite to the direction of the 
arrow 30, the connector 17 and the dampening screw 18 lie on the lower 
side of the pressure cylinder 1. 
The connector 17 for the pressure medium feed and with this also the 
dampening screw 18 can be quickly and easily shifted to the most 
accessible side of the pressure cylinder 1. This is made possible in the 
first place in that the cap 12 according to the invention is no longer 
attached to the cylinder housing 2 for the fastening of the sealing strips 
on or in the longitudinal slot 6, but rather in that individual clamping 
elements 11 are used for this purpose. 
From the representation in FIG. 4, it can be seen that these rotations of 
the cap and the connector locations are also possible in embodiments which 
are provided with a dampening apparatus. This is traced back to the 
rotationally symmetrically constructed connection channel 27, which 
ensures in every position of the cap 12 that the dampening channel 26 is 
connected to the connection hole 28 leading to the throttle 29. If the 
dampening tap 14 proceeds into the dampening cylinder 15 in the drive 
piston 4 and the central channel 16 essentially is closed, a compression 
of the pressure medium results out of the annular space around the 
dampening taps 14 through the dampening channel 26, the connection channel 
27, and the connecting hole 28 to the throttle 29 and from this to the 
connector 17. The cap 12 can thus be shifted in any desired position with 
this embodiment. 
Further, it is not difficult to see that, in the pressure cylinder 
according to the invention, the cap 12 can be constructed not only as a 
rectangle, but also square, or it can have entirely any desired 
multi-angular form. It is merely necessary that the cap not be attached 
for the tensile fastening of the sealing strips and that the hold-down 
bolts 13, as well as the channel path on the interior of the cap, are 
arranged symmetric to the center which represents the base requirements 
for the ability to turn the cap in an orderly fashion. Finally, the cap 
can also be constructed cylindrically. 
Independent of the outer geometrical form of the cap, it is possible to 
shift the cap not only stepwise, but also continuously rotatable. An 
embodiment of this variation of the invention is shown in FIG. 6. The cap 
12 is cylindrically constructed and extends into the cylindrical interior 
space 3 with a cylindrical attachment 22, which is sealed against the 
interior with the help of a gasket 21. The two sealing strips not 
represented are also fastened here with clamping elements 11. The two caps 
themselves are fastened onto the cylinder housing 2 by means of hold-down 
bolts 13, whereby the number of the hold-down bolts 13, their location and 
form of construction are arbitrarily chosen. Further, the function of the 
hold-down bolts can be carried out by parts of the machine stand into 
which the cylinder is installed as a whole. 
In FIG. 6, it follows that the hold-down bolts 13 grip a carrier frame 31 
provided behind the cap 12, in which the cap 12 can be rotated as mounted 
by means of a centrally extending cylindrical projection 32. By loosening 
the hold-down bolts 13 the cap 12 can be rotated continuously in this 
manifestation example about its axis in both directions, so that the 
connector 17 for the pressure medium together with the dampening screw 18 
can be shifted to any desired position continuously. The prerequisite here 
is again that the sealing strips not be fastened by means of the cap 12, 
but by individual clamping elements 11 and that the channel lines in the 
interior of the cap 12 be constructed rotationally symmetrical. 
Lastly, it is especially an advantage for the user to provide for the 
possibility of mounting the cap in horizontal or vertical orientation, 
thus in right-angled positions to the machine stand, while the lateral 
connector with the connecting flange can be arranged in an inclined form, 
relatively, between 0.degree. and 90.degree., according to the starting 
view point. This inclined drive position can, as a rule, contribute to the 
solution of difficult position relationships or force connections.