FI64449C - GLIDRINGSTAETNING FOER AXELN TILL CENTRIFUGALMASKINER SAERSKILT CENTRIFUGALPUMPAR - Google Patents

Description

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Patent and Registration Office (44) Nlhtivlkllpanon). ui VAT, .- on

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Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 26157 ^ 3-7 Proven-Styrkt (71) Wernert-Pumpen GmbH, Oberhausener Strasse 67-77, U33 Miilheim / Ruhr, Federal Republic of Germany-Förbundsrepubliken Tyskland (DE), (72) Friedrich Ratingen-Breitscheid, Helmut Denda, Oberhausen,

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (7U) Lei tzinger Oy (5U) Slip ring seal for the shaft of centrifugal machines, in particular centrifugal pumps - Glidringstätning för axeln account centrifugalkiner särskilt centrifugalpumpar

The invention relates to a mechanical seal for a shaft of centrifugal machines, in particular centrifugal pumps, in which the shaft passing through the sealing chamber of the pump housing is surrounded by an elastic bellows which, on the impeller side, against a fixed sealing ring.

In known slip ring seals of the above-mentioned quality, the bellows surrounding the shaft is in place and is pressed against the sealing ring surrounding the shaft or impeller in the bellows.

In centrifugal pumps made of plastic, such a sealing device can be problematic because predetermined operating conditions cannot be monitored, i.e., the pumps can, for example, occasionally run dry without liquid or for a longer time with their own liquid. In such applications, the frictional heat generated between the slip rings as a result of temperatures above 200 ° C will be transferred to the plastic components and can lead to their failure.

In the device shown in the introduction, the flexible bellows is convexly rotationally symmetrical. Since the production side must always be under overpressure relative to the atmosphere, the prestress of such an outwardly formed corrugated bellows (sealing collar) is converted by the fluid pressure into an axial stress which receives an increasing pressure, resulting in a higher compression pressure between the sliding ring surfaces. The pressure of the supply fluid in the shaft bushing depends essentially on the feed height of the pump and thus also on the operating speed. In addition, the feed, the quality of the relief reliefs on the compensating bores and the rear vanes and the operating status of the pump are affected.

The mechanical seal according to the invention allows the compression pressure to increase with a certain speed. Due to the bulging due to the centrifugal forces that become strong in the rotating corrugated bellows, the aim is to shorten the corrugated bellows and with it to reduce the elastic compression pressure. However, at the same time, the pressure increases in the slip ring state as the speed increases, resulting in the opposite effect to the centrifugal forces. When both effects are proportional mainly to the square of the speed, an equalization of the centrifugal forces is obtained so as to obtain, as constant as possible, a constant compressive pressure of the sliding ring parts sliding against each other.

Accordingly, the main object of the invention is to provide a mechanical seal of the quality described in the definition of the species, so that, among other things, any damage to the plastic impeller due to excessive temperature action on this impeller can be avoided due to the ability to compensate for centrifugal forces.

According to the invention, this object is solved mainly by fitting a sleeve rotating with the shaft at the end of the shaft, by having a larger diameter on the impeller-side sleeve to form a gap between the shaft and the sleeve and by turning the impeller-side bellows end inwards to form an inner pocket. and the end of the sleeve receives this inner pocket or goes into this inner pocket, the end of the pocket resting under pressure against the back side of the impeller hub.

In this way, the heat generated on the side of the friction heat impeller, i.e. on the impeller, is avoided so that the plastic impeller cannot be damaged by heat generation. The sliding rings sliding against each other are located at the end of the bellows away from the impeller.

The drawing shows a section of the essential parts of a centrifugal pump according to an embodiment.

The shaft 1 in the pump housing 2 has an impeller 3 made of thermoplastic. The shaft 1 passes through the sealing chamber 4 of the pump housing 2.

A mechanical seal is arranged in the sealing chamber 4 between the cover 16 of the sealing chamber 4 and the impeller 3. In this case, a sleeve 5 is arranged on the shaft 1, which rotates with the shaft. The end 6 of the sleeve 5 on the impeller 3 side is widened in diameter, as a result of which there is a gap 7 between the shaft end and the sleeve end. The bellows 8 surrounding the shaft are turned inwards from the impeller 3 side and thus form a pocket. The outer end 10 of the pocket abuts the impeller hub. The bellows rotates with the shaft 1 and the impeller 3.

The other end 11 of the bellows 8 is provided with a sealing ring 12.

In addition, the end 11 of the bellows engages in a ring groove in the end face 13 of the sealing ring, which has a conically outwardly extended cross-section. The second end face of the sealing 12 is also located opposite the sliding ring 15, which is fixed in place on the cover 16 of the sealing chamber 4.

The bellows 8 is bulged outwards and is under the pressure of the feed liquid, which feed liquid is led through the channel 17 to the chamber 4.