Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1992-08-28
1994-10-04
Cuchlinski, Jr., William A.
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
277 65, 277 81R, 277100, F16J 1534
Patent
active
053519728
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a shaft packing for sealing of rotating machine parts in order to prevent penetration by a medium in a container or the like.
At lead-through shafts in e.g. pumps and mixers the rotating shaft must be sealed against the stationary portion, e.g. the pump housing, in order to prevent that fluid penetrates at the transition between the rotating and stationary portions.
For the shaft packings of this type existing today most often a large part of the packing, including the spring package biasing the packing, is present in the container to be sealed.
This leads to it being a great risk by the packings of today that fluid penetrates from behind the packing, into the spring unit and all corners of the packing. Within food industry this is a severe problem, as colonies of bacteria rapidly are formed in the packing.
Within the cellulose industry, fibrous liquid can penetrate into the spring unit, whereby depositions are built up on the springs. The elasticity is decreased or lost and the packing starts to leak.
In order to eliminate the above defects double packings are arranged with a flushing between the packings. In this respect springs and the components of the packing have been present in the flushed space.
From aseptic viewpoint this space is adjacent the product only separated by the sealing surfaces, which is unsatisfying as a possible growth of bacteria in the flushed space may "migrate" through the sealing surface to the product.
Likewise, the flushing medium is often contaminated and limy which means that coatings are formed on the springs, eventually restraining their movements.
Yet another problem is that one does not always have control over the sealing. The wear and tear of the slide rings must be taken up by the elastic portion of the sealing, and wedge sealings wear and tear on the shaft by the wedge portion constitutes an additional uncontrollable factor.
Still another problem with the shaft packings of today is that it is difficult to axially fix the packing in the right position and that they can be difficult to reach in order to tighten the stop screws in the rear edge of the packing if it is built in, e.g. a stuffing box space.
In order to lubricate the packing and to take away small particles that are detached during the rotation it is common to arrange a flushing of the shaft packing.
An object with the present invention is to provide a shaft packing which is totally encased and moreover has a smooth and hygienic surface both on the product side and in the flushed space. Whereby there are no pockets or the like collecting the sealed medium.
A further object with the present invention is to provide a shaft packing in which angular variations of the shaft do not lead to wear and tear of the shaft packing, because the angular variations are taken up by a non-rotating part.
Still another object with the present invention is to provide flushing of the shaft packing in order to lubricate the sealing surfaces and to flush away possible contaminants. In one embodiment of the invention it is not necessary that the pressure of the flushing is higher than the pressure of the container to be sealed. The hydraulic balancing of the sealing surfaces is so formed that the sealing surfaces will receive a positive closing action from the pressure of the flushing and the pressure of the product, respectively, in spite of their mutual pressure relation.
These objects are achieved by a shaft packing according to the claims. Which shaft packing comprises a double sealing with an outer and an inner sealing that are biased to an intermediate ring by means of a spring package. The spring package is placed on the outside of both the medium to be sealed off and the flushing space, whereby there is no risk that the medium from the container, which in the food industry often contains particles and fibres, comes into contact with the spring package and thereby disturb its function or form growth of bacteria. Thus, it is possible to design the flushed space with completely smooth surfaces
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H. Hugo Buchter; "Industrial Sealing Technology"; Jul. 1986; pp. 141, 143-146, 148-149.
Cuchlinski Jr. William A.
Cummings Scott W.
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