Expansible chamber devices – Sealed opening in longitudinal wall of chamber for receiving...
Reexamination Certificate
1999-06-29
2001-09-04
Ryznic, John E. (Department: 3745)
Expansible chamber devices
Sealed opening in longitudinal wall of chamber for receiving...
C277S345000
Reexamination Certificate
active
06283010
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a piston rod-less pneumatic cylinder, with 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 exhibits 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, and with an outer band that at least partially covers the longitudinal slot from outside on either side of the piston, wherein this outer band exhibits fixing elements that engage the fixing elements of the sealing tape to secure the sealing tape in the longitudinal slot, with the sealing tape being spaced apart from the walls of the longitudinal slot except for the sealing areas.
2. The Prior Art
Piston rod-less pneumatic cylinders vary widely in design, and are most often used as pneumatically actuated working cylinders in arrangements where the smaller fitting length is advantageous relative to cylinders with piston rods. The force exerted on the piston by the pressure medium is conveyed from the transmission element that 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 sealing cuffs on the piston, and also by the sealing tape abutting from the inside on the longitudinally extended sealing areas near the end of the longitudinal slot, wherein the sealing tape is routed through in the inside under the transmission element of the piston in the unpressurized area between the piston seals.
The sealing tape is pressed against the longitudinally extended sealing areas by the pressure prevailing in the respectively pressurized cylinder interior. However, precautions must normally be introduced to prevent the sealing tape from sagging into the interior when the latter is in an unpressurized state, since this would result in at least a temporary leak as pressure begins to build in this previously unpressurized interior.
In the above connection, for example, EP 69 199 B1 discloses a pneumatic cylinder of the kind mentioned at the outset in which an outer band that covers the longitudinal slot from outside to prevent foreign objects, contaminants and the like from penetrating is provided simultaneously to hold the inner sealing tape. To this end, the fixing strip located centrally in the sealing strip or sealing tape exhibits projections on both sides as longitudinally extended fixing elements that are overlapped by two accompanying ledge-shaped fixing elements of the outer band. As a result, the sealing tape is held with an overall positive fit to the outer band, and hence in the longitudinal slot, even if no pressure is acting on the sealing tape from the inside. Since the longitudinal slot itself can remain free of fixing grooves and the like, the cylinder tube is relatively simple in design, wherein the transmission element can also be laterally guided or supported in the longitudinal slot.
The only disadvantage to the discussed known design is the fact that engaging and disengaging the sealing tape mount on the outer band does require relatively high forces due to the joint with a positive fit, which must be taken into account in the structure and design of the interacting bands, in particular to prevent the outer band from becoming drawn into the longitudinal slot or lifting off of the longitudinal slot due to the inner sealing tape. The object of this invention is to avoid the mentioned disadvantages, in particular to improve a pneumatic cylinder of the kind mentioned at the outset in such a way as to simplify the securing of the sealing tape during the safe operation of the arrangement.
SUMMARY OF THE INVENTION
The object is achieved according to the invention for a pneumatic cylinder of the kind mentioned at the outset by having the fixing elements on the sealing tape and outer band interact in a purely frictionally engaged manner. Surprisingly, it was discovered that the lower retention forces to be applied are entirely sufficient to hold the inner sealing tape reliably in the slot or have it form a seal on the longitudinally extended sealing areas near the end of the longitudinal slot on the cylinder interior, even with the cylinder space lying below in an unpressurized state. As a result, the described leaks can be avoided without the mentioned problems relating to the outer band coming about due to excessively high forces to be overcome while joining or separating this connection.
In a preferred embodiment of the invention, the outer band is designed as a single unit, and exhibits essentially striated fixing elements to hold the sealing tape on its side facing the interior of the cylinder tube. This simple design is similar in some way to the one de scribed above relating to prior art, except that retention is purely frictional here, and does not involve a positive fit.
In another preferred embodiment of the invention, however, the outer band can be divided in a longitudinal direction, and the fixing strip of the sealing tape can be securely held in between the two parts. As a result, the divided outer band and the inner sealing tape secured in between together take over the function of covering the longitudinal slot on the outside. The divided outer band held in a groove, e.g., through clamping, is safeguarded even more against being drawn into the longitudinal slot in this variant.
In another preferred embodiment of the invention, the sealing tape along with, advantageously, the outer band can consist of a flexible material, preferably plastic, e.g., polyurethane, 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 tape and band in accordance with practical requirements.
REFERENCES:
patent: Re. 33637 (1991-07-01), Hoglund
patent: 4733604 (1988-03-01), Lipinski
patent: 4991494 (1991-02-01), Migliori
patent: 5467686 (1995-11-01), Lipinski
patent: 5517901 (1996-05-01), Lipinski
patent: 3124878 C1 (1982-12-01), None
patent: 0068088 (1983-01-01), None
Fritz Erhard
Rohatschek Peter
Dykema Gossett PLLC
Hygrama AG
Ryznic John E.
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