Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Patent
1997-12-11
2000-04-04
Knight, Anthony
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
277489, 277490, 277946, F16J 916
Patent
active
060451351
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a sealing ring disk for a seal at a piston rod.
2. Description of the Prior Art
Dry running piston compressors are machines which require no foreign lubrication in the compression part. Such compressors have fixed sealing elements past which a piston rod is moved. With such an arrangement, a plurality of seal elements are usually arranged pair-wise one after the other in series forming a so-called packing. A pair of seal elements arranged in a packing in this manner is known from DE-42 01 246 C2. This arrangement and design of seal elements has the disadvantage that in each case two seal elements are to be placed lying adjacent to one another in the direction of motion of the piston in order to fulfil the seal function. A known problem of such seals at piston rods is the arising heat of friction. Conveying off the heat of friction via the seal elements themselves is possible only to a limited extent, since the seal elements are usually made of plastic and act thermally nearly as insulators. The greatest portion of the heat of friction is thus led off in a clearly less efficient manner by the piston rod. The arising heat of friction is thus largely responsible for a high degree of wear. Thus, a complicated and expensive cooling of the packing containing the sealing elements is often required.
The object of the present invention is to overcome these known disadvantages of sealing elements.
SUMMARY OF THE INVENTION
The sealing ring disk in accordance with the invention is suitable, in particular, for dry running ring piston compressors, with the sealing ring disks consisting of a plastic with self-lubricating properties. Such sealing ring disks are used e.g. as piston rod seals (stuffing box, packing) in which the piston rod is moved past the fixed seal elements. As a result of the low heat resistance of polymer sealing materials the heat of friction which arises can lead to substantial thermal problems. An advantage of the sealing ring disk in accordance with the invention is to be seen in the fact that the sealing ring disk can be made relatively thin in the direction of the piston rod; and, in comparison with the cited state of the art, a single sealing ring disk suffices to ensure the seal function instead of the two sealing rings as previously. The relatively thin sealing ring disk in accordance with the invention has the advantage that an increased heat flow is possible through radiation from the piston rod to the metal housing of the packing, since the sealing ring disk that acts as an insulator has smaller dimensions, and that the ratio of the portion of the piston rod surface not covered over by seal rings to the sum of the seal ring contact area is substantially more favorable. A further advantage of the sealing ring disk of the invention is to be seen in the fact that the radial partition joints known from the current state of the art can be dispensed with. For this reason it is no longer necessary to use two sealing ring disks lying adjacent to one another, but rather the use of a single sealing ring disk suffices. Suitable materials for the sealing ring disk are plastics for dry running applications such as filled polymers with a matrix of polytetrafluoroethylene (PTFE) or a mixture of mechanically solid, high-temperature-resistant and wear-resistant modified polymers such as polyetheretherketone (PEEK), polyetherketone (PEK) polyimide (PI), polyphenylene sulphide (PPS), polybenzimidazole (PBI), polyamidimide (PAI) or even epoxy resin.
The sealing ring disk in accordance with the invention can be manufactured of modified PEEK. This has the advantage that very thin rings can be manufactured so that, on the one hand, the piston rod can better transmit the heat via radiation to the packing and, on the other hand, a smaller frictional area exists between the seal ring and the piston rod, which also reduces the heating. Too much heating up of the piston rod can be avoided in this manner, which has the advantage that the
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Knight Anthony
Maschinenfabrik Sulzer-Burkhardt AG
Pickard Alison K.
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