GB1594647A

GB1594647A - Sealing device with metallic surfaces for rotating members

Info

Publication number: GB1594647A
Application number: GB1721878A
Authority: GB
Original assignee: Fluiten Italia
Current assignee: Fluiten Italia
Priority date: 1977-05-02
Filing date: 1978-05-02
Publication date: 1981-08-05
Also published as: DE2818664A1; DE2818664C2; IT1071334B

Description

(54) SEALING DEVICE WITH METALLIC SURFACES FOR ROTATING MEMBERS (71) We, FLUITEN ITALIA S.p.A. of Via Albani 29, Milan, Italy, an Italian Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a sealing device with metallic surfaces for rotating members in general, such as the shafts of pressure containers.

To operate certain mechanical members, for instance, the agitators of autoclaves or the pumps of centrifugal compressors, it is necessary to follow certain criteria in order to ensure not only the desired mechanical result, but also a sealing effect at the driving shaft which projects from the pressure container.

In a known arrangement, the said sealing action was realised by means of pairs of metal rings which cooperated face against face, while the fluid and the ambient pressure acted upon the said pairs.

However, the sealing members known in the art present some drawbacks due to the metal surfaces which are in contact with one another, to the pressure provided by such rings and to the operational speeds.

According to the invention, there is provided a sealing device for a shaft of a pressurized container comprising a first member partly defining a first annular or interrupted annular chamber and having a first metallic sealing surface, and a second member partly defining a second annular chamber, which is coaxial with the first annular chamber and communicates therewith via one or more ducts, and having a second metallic sealing surface cooperating with the first sealing surface to form a substantially annular seal, having portions extending radially inwardly and outwardly from the first chamber, one of the first and second chambers being provided with an inlet for receiving a fluid under pressure, the second member being arranged to be axially slidable with respect to the shaft, the second annular chamber being partially defined by a third member which is arranged to be axially fixed with respect to the shaft and the areas of the surfaces of the first, second and third members defining the first and second annular chambers being arranged so that, when a fluid under pressure is supplied via the inlet, the first and second sealing surfaces are urged towards each other.

At least one of the two sealing surfaces may advantageously haveat least one annular groove connected with the fluid source under pressure the said groove being designed to subdivide the surface concerned into two complementary surfaces, which are respectively arranged at the inside and the outside of the pressure container or vice versa.

To realise an automatic circuit of the lubricating and sealing fluid, the first annular chamber may be provided with an a axial depth or radial width which varies and may co-operate with a succession of cavities, each of which is angularly displaced with respect to the other and a number whereof is connected with the second annular chamber.

The invention will be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a cross-sectional view of a sealing group for a driving shaft of a stirrer for an autoclave or for a pump; Figure 2 is a cross-section through another preferred device; and Figures 3 and 4 are partial cross-sections along lines III - III and IV - IV of Figure 2.

In Figure 1, there is shown a driving shaft A and a sealing group B which incorporates a pre ferred device, the group being secured to an autoclave C.

The sealing group B comprises one flange 10, secured to the autoclave C by means of screws 12, the said flange being provided, at diametri cally opposite positions, with inlet and outlet connections 14 and 16 respectively, the inlet of which is connected to a fluid pressure gen erator and an outlet by means of limiting or throttling member. The fluid, which is let in through the connection 14, can consist either of a gas or of a liquid and in the last mentioned case the liquid can be an oil to lubricate the sealing members.

An axial duct 18 connects the connection 14 to a first annular groove 20 provided at one of the ends of a bush 22, which is retained in a corresponding seat in the flange 10 and whose end projects out of the flange. One pin 24, integral with flange 10, engages into an opening 26 of the bush 22, whereas packing (sealing) rings 28 ensure tight connection between the said parts and the exterior, or with the interior of the autoclave.

The annular groove 20, at the projecting end of the bush 22, serves to delimit, on the said end, two even and co-axial surfaces 30 and 32 respectively, shown as having the same radial width but which can have, if desired, different radial widths.

The said surfaces engage corresponding surfaces shown by one of the ends of a counterbush 34 which has formed there - in a complementary groove 35 to delimit, together with the grooves 20, an annular chamber 20 and 35.

The counter-bush 34 houses, at the other end thereof, one sleeve 36 retained by shaft A and having one or more pins 38 engaging with play corresponding openings 40 of the counterbush 34, to connect the said parts torsionally (rotationally) with each other.

The sleeve 36 is provided, in opportune positions, with axial openings 42, designed to house one part of spiral springs 44, the action whereof is exerted on an annular projection 46, inside of and toward one of the ends of the counter-bush 34, in such a way that the annular surfaces 30 and 32 of the bush 22 and of the counter-bush 34 are pressed against each other.

The counter-bush 34 has formed therein at least one axial opening 48 connecting the annular chamber 20 and 35 with a second annular chamber 50, formed between the sleeve 36 and the annular projection 46 of the counter-bush 34. Elastic gaskets 52 and 53, shown around the sleeve 36, provide a fluidtight connection between the fixed and the movable parts of the preferred device and in particular, between the chamber 50 and the interior (or exterior) of the autoclave.

Another preferred embodiment is shown in Figures 2 to 4 of the drawings, in which like parts are referred to by like reference numerals, a bushing 22a of the device having an annular groove 20a (see also Figure 3) extending over less than 360" The groove 20a connects, at an initial part thereof, with an axial duct 1 8a connected to a connection 14a, for the inlet of a fluid under pressure, whereas the final part of the groove 20a ends next to the initial part and is separated from the latter by means of a sealing area 58, being connected by means of a corresponding axial duct 19, to an outlet connection 1 6a for the outlet of the fluid under pressure.

The radial cross-section of the groove 20a, i.e. the depth thereof increases from the inlet duct 18a, until reaching a maximum depth at the medium part 21 of the said groove, that is, in a position which is diametrally opposite the sealing area 58. Beginning from the said maximum cross-section, the depth and hence the radial cross section of groove 20a decreases, until it becomes substantially equal to nought, next to the outlet duct 19.

The counter-bush 34a presents a plurality of axial openings 48a (see also Figure 4), in order to connect in this way the groove 20a to a chamber 50a which corresponds to the annular chamber 50 shown in Figure 1.

One or more cavities 60 are provided between the axial openings 48a, these cavities 60 being spaced apart by less than the angular width of the sealing area 58/of bush 22a As a consequence, during the rotational mo tion of the couter-bush 34a, an automatic circu lation of the cooling fluid is realised. In partic ular, the lubrication and the pressurisation would otherwise require the use of pumps con ected with connections 14 and 16. In the pre sent case, connections 14a and 16a can be connected to an adjusting member,by means of whic the fluid circulation, as well as the lubricating and pressurising circulation, can be adjusted.

As a consequence and according to the fore going description, or in both cases, the fluid under pressure, which is let in through the connection 14, flows into the annular chambers 20, 35 and 50, to establish, in the said chambers, different pressures, the resultant pressure of which is due to the action of the pressure in the chamber 50, which shows a greater surface than that of the chamber 20, 35. To the last mentioned surface sums the action provided by springs 44, thus ensuring the connection be tween the surfaces delimited by the annular chamber 20, 35. Furthermore, the fluid under pressure, contained in the chamber 20, 35, tends to leak through the sealing surfaces 30 and 32, which are, however, at all times, pressed against each other, by means of the pressure present in the chamber 50.In any case, eventual losses of the fluid present in the chamber 20, 35 will always occur at one of the sealing surfaces 30 or 32, which are connected with the exterior. For example, if a loss of pressurised fluid occurs at the inner surface 32, the fluid flows into a free space 54 formed be tween the bush 22 and the sleeve 36. Therefore, a fluid-tight connection is at any time ensured between the rotating parts, even if the said parts are moving at high speeds.

Furthermore, it is possible to introduce the fluid into the chambers 20, 35 and 50 under any desired pressure, without moving the sea ling surfaces 30 and 32 apart from each other by effect of the same pressure, also because it is possible to realise an optimum balance between the forces which tend to move the said surfaces away from each other and to open the same and between the forces which tend to close the said surfaces.

As previously mentioned, the fluid which is introduced into the chambers 20, 35 and 50 can advantageously consist of a lubricating oil, thus also providing a cooling action of the sur faces in contact with one another, by avoiding or limiting, during the realisation of the device, the use of very hard materials, such as those which are necessary in the case of the known sealing members.

With the sealing device as previously described, the above mentioned results, as well as others, are realised. In particular, it is possible to guarantee the efficiency of the seal, also when abrading products are present or if such products are machined.

In the case of the variation shown in Figures 2 to 4, it is not necessary to provide circulating pumps.

It is possible to modify and to vary the device, with particular reference to the operational characteristics thereof. For example, the device can be provided with several pairs of sealing surfaces, disposed in axial and/or in radial succession, to form an integrating part for the support of the shaft A The widths of the sealing surfaces 30 and 32 can advantageously vary from each other, also in relation to the different action which is to be obtained. Furthermore, in the case of the embodiment shown in Figures 2 to 4, the opening of chamber 20a can have a variable width beween the ducts 1 8a and 19 and the medium part 21. For instance, the said opening can have a spiral development.

Furthermore, the dimensions of the recesses 60 can advantageously vary, with particular reference to the angular width thereof, thus developing in the form of arch-shaped sectors, as shown by the dotted lines 35a of Figure 4, so as to embrace an area of the desired angular width of the chamber 20a.

The device can be put to various uses. For instance, it may be fitted not only to autoclaves, but also to pumps and centrifugal compressors, to mixers, stirrers, etc.

The rotating part of the seal can be equally provided either at the inside or at the outside of a container in which the treatment is to take place.

WHAT WE CLAIM IS: 1. A sealing device for a shaft of a pressurized container, comprising a first member partly defining a first annular or interrupted annular chamber and having a first metallic sealing surface, and a second member partly defining a second annular chamber, which is coaxial with the first annular chamber and communicates therewith via one or more ducts, and having an second metallic sealing surface cooperating with the first sealing surface to form a substantially annular seal having portions extending radially inwardly and outwardly from the first chamber, one of the first and second chambers being provided with an inlet for receiving a fluid under pressure, the second member being arranged to be axially slidable with respect to the shaft, the second annular chamber being partially defined by a third member which is arranged to be axially fixed with respect to the shaft and the areas of the surfaces of the first, second and third members defining the first and second annular chambers being arranged so that, when a fluid under pressure is supplied via the inlet, the first and second sealing surfaces are urged towards each other.

2. A device as claimed in claim 1, in which there is provided spring means urging the first and second sealing surfaces towards each other.

3. A device as claimed in claim 1 or 2, in which there is found in each of the first and second members a respective annular groove dividing each of the first and second sealing surfaces into radially inner and outer annular sealing surfaces and communicating with the inlet.

4. A device as claimed in Claim 3, in which the radially inner and outer sealing surfaces have substantially the same radial width.

5. A device as claimed in Claim 3, in which the radially inner and outer sealing surfaces have different radial widths.

6. A device as claimed in any one of Claims 3 to 5, in which the annular grooves are co-axial to one another and in communication with an outlet for the fluid.

7. A device as claimed in any one of Claims 1 to 6, in which the third member comprises a sleeve keyed to the shaft of the pressurised container, the sleeve retaining the second member which comprises a bush torsionally restrained to the sleeve, the bush being provided, at one of its axial ends with an annular groove having at the one side thereof the second sealing surface, and being provided with a movable wall partially defining the second annular chamber, the bush being axially movable with respect to and guided by the sleeve.

8. A device as claimed in any one of Claims 1 to 7, in which the first and second sealing surfaces each have first and second peripheral edges disposed in the ambient and in the pressurised container, respectively.

9. A device as claimed in any one of Claims 1 to 8, in which the first annular chamber has a depth in the axial direction which varies so as to realise a pumping effect for the circulating fluid.

10. A device as claimed in any one of Claims 1 to 9, in which the first annular chamber has a width in the radial direction which varies so as to realise a pumping effect for the circulating fluid.

11. A device as claimed in Claim 9 or 10, in which the depth or width of the first annular chamber varies from a maximum to zero and forms between the inlet and an outlet of the fluid under pressure a sealing area in such a way that the area with a greater depth or width of the first annular chamber is disposed substantially in a position opposed to the said sealing area.

12. A device as claimed in any one of claims 9 to 11, in which the first annular chamber has a circumferential extent of less than 360" and is delimited by the inlet duct and by a or the outlet duct for the fluid under pressure.

13. A device as claimed in any one of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. which are necessary in the case of the known sealing members. With the sealing device as previously described, the above mentioned results, as well as others, are realised. In particular, it is possible to guarantee the efficiency of the seal, also when abrading products are present or if such products are machined. In the case of the variation shown in Figures 2 to 4, it is not necessary to provide circulating pumps. It is possible to modify and to vary the device, with particular reference to the operational characteristics thereof. For example, the device can be provided with several pairs of sealing surfaces, disposed in axial and/or in radial succession, to form an integrating part for the support of the shaft A The widths of the sealing surfaces 30 and 32 can advantageously vary from each other, also in relation to the different action which is to be obtained. Furthermore, in the case of the embodiment shown in Figures 2 to 4, the opening of chamber 20a can have a variable width beween the ducts 1 8a and 19 and the medium part 21. For instance, the said opening can have a spiral development. Furthermore, the dimensions of the recesses 60 can advantageously vary, with particular reference to the angular width thereof, thus developing in the form of arch-shaped sectors, as shown by the dotted lines 35a of Figure 4, so as to embrace an area of the desired angular width of the chamber 20a. The device can be put to various uses. For instance, it may be fitted not only to autoclaves, but also to pumps and centrifugal compressors, to mixers, stirrers, etc. The rotating part of the seal can be equally provided either at the inside or at the outside of a container in which the treatment is to take place. WHAT WE CLAIM IS:

1. A sealing device for a shaft of a pressurized container, comprising a first member partly defining a first annular or interrupted annular chamber and having a first metallic sealing surface, and a second member partly defining a second annular chamber, which is coaxial with the first annular chamber and communicates therewith via one or more ducts, and having an second metallic sealing surface cooperating with the first sealing surface to form a substantially annular seal having portions extending radially inwardly and outwardly from the first chamber, one of the first and second chambers being provided with an inlet for receiving a fluid under pressure, the second member being arranged to be axially slidable with respect to the shaft, the second annular chamber being partially defined by a third member which is arranged to be axially fixed with respect to the shaft and the areas of the surfaces of the first, second and third members defining the first and second annular chambers being arranged so that, when a fluid under pressure is supplied via the inlet, the first and second sealing surfaces are urged towards each other.

13. A device as claimed in any one of

Claims 9 to 12, in which the second sealing surface has a plurality of circumferentially spaced cavities disposed opposite the first annular chamber, the cavities being interposed between the openings of the ducts which connect the two annular chambers with one another.

14. A device as claimed in Claim 13, in which the angular distance between adjacent recesses and between each adjacent recess and duct is less than the angular width of the sealing area between the inlet duct and a or the outlet duct of the first chamber.

15. A sealing device for a shaft, substantially as herein-before described with reference to Figure 1 of the accompanying drawings.

16. A sealing device for a shaft, substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.

17. A support for the shaft of an autoclave or the like, including a sealing device as claimed in any one of Claims 1 to 16.