Expansible chamber devices – Sealed opening in longitudinal wall of chamber for receiving...
Reexamination Certificate
1999-06-30
2001-11-27
Ryznic, John E. (Department: 3745)
Expansible chamber devices
Sealed opening in longitudinal wall of chamber for receiving...
Reexamination Certificate
active
06321636
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a piston rod-less pneumatic cylinder, that includes a piston longitudinally movable inside a cylinder tube and a transmission element that engages with this piston and projects out through a longitudinal slot in the cylinder tube, along with a sealing tape that seals the longitudinal slot from the inside on either side of the piston, which is routed through the piston in the area of the transmission element, and includes a sealing strip that interacts with two longitudinally-extending sealing areas near the end of the longitudinal slot inside the cylinder, along with at least one fixing strip arranged on the outside of the sealing strip with two fixing elements that lie opposite one another relative to the center plane of the longitudinal slot, and are essentially longitudinally extended and directed toward the outside.
Pneumatic cylinders of the above kind are mostly pneumatically actuated and, due to their piston rodless design, have come to be preferred for use in areas where small fitting length is important. The force exerted on the piston by the pressure medium is conveyed from the transmission element that engages with the piston and projects out through the lateral longitudinal slot to the device to be operated. The delivery chambers lying on either side of the piston are sealed off by packing rings or the like on the piston, and also by the sealing tape covering the longitudinal slot, which is routed toward the inside under the transmission element in the unpressurized area between the piston seals.
2. The Prior Art
The operating pressure prevailing in the respective delivery chamber during actuation of the pneumatic cylinder presses the sealing tape from the inside against the two longitudinally extended sealing areas in the area of the end of the longitudinal slot inside the cylinder, forming a seal. In an unpressurized state, however, precautions must in most instances be taken to prevent the sealing tape from sagging into the cylinder, since at least a temporary leak will otherwise arise during pressurization with the pressure medium. For this reason, one design for a pressure cylinder of the kind mentioned at the outset, e.g., as known from EP 82 829 B1, provides for outwardly directed, longitudinally-extended fixing elements that flexibly press outwardly against the side walls of the longitudinal slot, thereby using clamping and friction forces to bring about a non-positive fit of the sealing tape in the longitudinal slot. EP 147 803 B1 also discloses a similar design, in which the central area of the side walls of the longitudinal slot exhibits rebounding recesses that are expanded relative to accompanying longitudinally extended, projecting fixing lips on the fixing strip of the sealing tape. As a result, the sealing tape is here finally held in a non-positive manner in the longitudinal slot of the cylinder tube by clamping and frictional forces.
In both mentioned known arrangements, in particular in applications involving exposure to strong vibrations or the like, for example, there is a danger that the sealing tape on the unpressurized side will still sag into the cylinder, as a result of which the described initial leaks can become noticeable in a correspondingly disruptive fashion during pressurization. The object of this invention is to avoid the mentioned disadvantages to known arrangements, in particular to design a pneumatic cylinder of the kind discussed at the outset in such a way as to ensure that the sealing tape will hold better in the longitudinal slot using simple means, even in an unpressurized state.
SUMMARY OF THE INVENTION
The object is achieved according to the invention in a pneumatic cylinder of the kind mentioned at the outset by having the fixing elements of the fixing strip engage the fixing edge provided on the cylinder with a positive fit to hold the sealing tape in the longitudinal slot. This makes it very easy to ensure that the sealing strip or its sealing areas always interact with the accompanying longitudinally extended sealing areas around the interior cylinder end of the longitudinal slot even on the unpressurized side. As a result, the longitudinal slot is already sealed as pressurization of the respective cylinder side begins, and the described leaks virtually become no longer discernible.
In a preferred embodiment of the invention, the fixing edges can be formed on the longitudinal slot of the cylinder tube itself. On the one hand, this simplifies the manufacture of cylinder tubes, which are today most often extruded out of aluminum, and of the fixing strip of the sealing tape. On the other hand, this makes it relatively easy to engage or disengage the joint holding the sealing tape in the longitudinal slot.
In another advantageous embodiment of the invention, the fixing edges can also be arranged on separate fixing grooves of the cylinder tube provided on the interior on either side, essentially parallel next to the longitudinal slot. This permits the greatest variety of potential configurations for these fasteners and, for example, leaves the longitudinal slot available as a lateral support for the projecting transmission element.
In another preferred embodiment of the invention, the fixing edges can also be provided on an outer band that at least partially covers the longitudinal slot from outside. This simplifies the cylinder tube profile and its manufacture, since it shifts the corresponding measures to the area of the outer band.
In a further embodiment of the invention, the fixing edges can be formed directly by the outside edges of the longitudinal slot. This also enables a very easy forming of the cylinder tube profile while and a simultaneous reliable fixing or anchoring of the sealing tape.
In a further embodiment of the invention, the fixing edges formed on the longitudinal slot of the cylinder tube itself can be designed as fixing grooves provided on both sides of the side walls of the longitudinal slot, on the sides facing the interior of the cylinder tube. These fixing grooves preferably exhibit additional fixing edges on the opposing sides to secure a correspondingly designed outer band. As a result, these side fixing grooves can simultaneously accommodate an outer band that covers the longitudinal slot from outside to prevent dirt, foreign objects and the like from getting inside. This outer band is essentially identical or similar in designed to the inside sealing tape and arranged laterally reversed to the latter.
In a design with separate grooves provided essentially parallel next to the longitudinal slot, a further embodiment of the invention can provide that the side walls of the fixing grooves be undercut on the side facing away from the longitudinal slot, or preferably even on both sides, near the floor of the groove. The transition from fixing groove to undercut forms the fixing edge that interacts with the accompanying fixing element of the fixing strip. As a result, the sealing tape is very reliably secured with a positive fit near the two longitudinally extended sealing areas.
In another advantageous further development of the invention for fixing edges formed on the outer band, the outer band is divided in a longitudinal direction, and the sealing tape is held in between with the fixing strip. As a result, the longitudinal slot is sealed on the outside, and the inner sealing tape is secured. In this regard, no more additional precautions need to be met on the longitudinal slot.
In another preferred further development of the invention, the sealing tape along with, advantageously, the outer band preferably consist of plastic, with at least the sealing strip of the sealing tape exhibiting inserted or simultaneously formed linear reinforcements extending in the longitudinal direction, preferably made out of steel wire or kevlar fibers. This makes it possible to manufacture the sealing tape and outer band in accordance with practical requirements.
In the following, the invention will be explained in greater detail based
Fritz Erhard
Rohatschek Peter
Dykema Gossett PLLC
Hygrama AG
Ryznic John E.
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