GB1598337A

GB1598337A - Sealing arrangement

Info

Publication number: GB1598337A
Application number: GB52653/77A
Authority: GB
Original assignee: KARLSTAD MEKANISKA AB; Karlstads Mekaniska Werkstad AB
Current assignee: KARLSTAD MEKANISKA AB; Metso Fiber Karlstad AB
Priority date: 1976-12-20
Filing date: 1977-12-19
Publication date: 1981-09-16
Also published as: FI773795A; SE7614289L; NO160463C; NO774323L; JPS5377949A; NO160463B; DE2756527A1; FI65655B; NL7714114A; SE409895B; FI65655C

Description

(54) SEALING ARRANGEMENT (71) We, AKTIEBOLAGET KARL STADS MEKANISKA WERKSTAD, a Swedish Company of Verkstadsgatan 20, S-65101, Karlstad, Sweden, 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 arrangement between a first and a second part which are provided to rotate relative to each other.

O-ring sealings, i.e. sealings in which the sealing member is an O-shaped ring of resilient material of substantially circular cross-section, are in general used in the machine industry. In general a sealing arrangement of this type shows a groove in a first machine part, which groove is slightly more shallow than the cross-section of the ring, while the other machine part, which has to be tightened to the first part, exhibits a flat or cylindric surface, provided to be tightened against the O-ring by being pressed against the same. When there is a relative movement between the two machine parts, which is the case by the type of arrangement to which the present invention relates, wear of the ring as well as of the sealing surfaces ensues in the course of time.With parts of similar material the wear arises both in the groove and on the sealing surface of the other part as a result of the ring performing a relative movement in relation to both the sealing surface and to the groove, in which it floats. Because of said condition wear will occur on three parts in every sealing arrangement of this type, viz. on the ring and on the two machine parts, which makes repairs expensive and time consuming.

Another drawback with a ring in a floating arrangement in the groove is that the ring can twist round its own axis, which can cause leakage.

Thus the free arrangement of the ring in the groove, which usually has a rectangular cross-section, can result in certain drawbacks. However, this unobstructed movability of the ring in the groove is necessary with machine parts which perform an axial movement relative to each other e.g. piston rods, which represent a common sealing problem.

Accordingly the principle of a freely moving ring in the groove seems to be applied as a routine.

The present invention relates to a sealing for the tightening between parts, which rotate in relation to each other, and it is an aim of the present invention to eliminate the drawbacks mentioned by providing for li mited wear and further to remove the risks of undesired wear and leakage, which can be the result of the tendency of the sealing ring to twist in its groove.

A further aim of the invention is to provide that the wear and consequently also the need of repair will be restricted to one of the machine parts.

According to the present invention there is provided a sealing arrangement between parts which are arranged to rotate relative to each other with one part provided with a groove which partly encloses an O-ring of resilient material which in an uncompressed condition is of substantially circular crosssection, a surface on the other part pressing against the O-ring so that the O-ring is deformed and forms a seal between the groove and said surface, the surface of the groove being curved in transverse crosssection, the curvature of the groove surface at least in part and the resilient properties of the O-ring being selected so that the O-ring in the compressed condition rests against the major part of the surface of the groove along an unbroken line as seen in transverse cross-section and the length. of the O-ring surface, as viewed in transverse cross section, which engages said other part is less than the length of the O-ring surface, as viewed in the transverse cross-section, engaging the surface of the groove, whereby the O-ring is fixed in position in the groove but movable in relation to the surface of said other part.

According to a further feature of the present invention there is provided a sealing arrangement between a portion of a shaft and a bearing means in which the portion of the shaft is rotatable, comprising a body rigidly connected to the bearing means and provided with a surface in which an annular groove is made, an O-ring of resilient material and in uncompressed condition of substantially circular cross-section, being located in the groove and engaged by a first flat radially extending surface of a second ring of a non-resilient material located in a position between the O-ring and a flat radially extending surface belonging to the portion of the shaft, with a second flat radially extending surface of the second ring which is opposed to said first flat radially extending surface, bearing against the flat radially extending surface belonging to the portion of the shaft, the surface of the groove being at least in part curved in transverse cross-section, the curvature of the grove surface and the resilient properties of the O-ring being selected so that the O-ring in the compressed condition rests against the major part of the surface of the groove along an unbroken line as seen in transverse cross-section, and is pressed against said first flat radially extending surface of the said second ring, the length of the O-ring surface, as viewed in transverse cross-section, which engages said first flat radially extending surface being less than the length of the O-ring surface, as viewed in transverse cross-section, engaging the surface of the groove, whereby the O-ring is fixed in position in the groove.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows in an illustrative way the application of the invention in the form of a partial view of a cross-section through a blade seal for a propellor with pivotable blades; Figure 2 shows an enlarged view of part of Figure 1; Figure 3 shows a second embodiment of the present invention; Figure 4 shows a third embodiment of the present invention; and Figure 5 shows a propellor with pivotable blades of the kind to which the invention relates.

The figures 2, 3 and 5 are cross-sections corresponding to the cross-section in Figure 1 and are in an enlarged scale compared with the figures 1 and 5.

According to the figures 1 and 5 a propeller with pivotable blades has a hub 1, three propeller blades 26, each one with a flange 2 and shaft pivot 3, a bearing means 4 for the pivot 3 and a sealing arrangement 5.

According to Figure 5 the hub 1 is provided with an outer end portion 25. The inner end of the hub is mounted on a propeller shaft (not shown) by means of which it can be rotated. When in operation the hub 1 rotates along an axis, which is in line with the propeller shaft, the centre line of which extends in a direction, which in Figure 1 is perpendicular to the plane of the Figure.

The propeller blades 26, of which the flange 2 of one of the blades is shown in Figure 1, are pivotable about axes, which are perpendicular to the axis of rotation for the propeller hub and extend parallel to the axis of the respective pivots 3. Thus when pivoting the blades, the blade flanges 2 and consequently the pivots 3 rotate in relation to the respective bearing means 4 integrated in the propeller hub 1. The sealing between the relatively movable parts, i.e. between the propeller blade and the propeller hub 1 including the bearing means 4, is provided by means of the sealing arrangement 5, three embodiments of which are shown in more detail in the following with reference to the figures 2, 3 and 4.

The device according to Figure 2 has a stepped supporting ring 7, made of metal, which is sealed in a stationary position in the propeller hub 1 by means of a resilient sealing ring 8. On its lower step surface, the supporting ring 7 has a groove 9 in the shape of a segment of a circle. An O-ring 10 lies against the bottom of the groove 9, a sealing ring 11 of metal, resting with a surface 19 against O-ring 10, the O-ring 10 pressing the sealing ring 11 against the blade flange 2.

As is evident from figure 2, the distance between the bottom of the groove 9 and the sealing ring 11 in relation to the dimensions of the O-ring 10, is chosen in such a manner that the latter will be pressed to acquire an elongated cross-section and will rest along substantially the whole extension of the bottom of the groove 9 and forms a wide flat resting surface against the surface 19 of the sealing ring 11. As mentioned, the supporting ring 7 is stationary in the propeller hub and the material for the same can be chosen without consideration to bearing properties, and therefore a material having a great cavity resistance, by way of example nialbronze, can be chosen. For the sealing ring 11 a bronze of good bearing properties in relation to the blade flange 2 is chosen, which blade flange can be made of propeller bronze or stainless steel. For the O-ring 10 as well as for the O-ring 8 a synthetic rubber is chosen.

The embodiment according to figure 3 comprises a supporting ring 12 provided with a sealing ring 13 for the sealing of the propeller hub 1, and with a groove 14. An additional sealing ring 15 of metal with a second groove 16 is provided. O-rings 17 and 18 respectively are placed in the both grooves 14 and 16. The ring 17 seals against a surface 20 of the ring 15 and the ring 18 seals against a surface 21 of the blade flange 2.

The two grooves 14 and 16 for the O-rings are of different size, the groove 16 of the sealing ring 15 being smaller than the groove 14 of the supporting ring 12, but the shape is the same. Both the grooves show a flat bottom and sides perpendicular to the outer surface of the respective rings 12 and 15 and also to the bottom of the grooves. The grooves are provided with bottom radius, the measure of which is about one half of the depth of the groove. The topedges of the sides are rounded off. When the parts are pressed together in their mounted positions, the O-rings 17 and 18 are compressed between their resting surfaces and are pressed out to acquire an oblong shape, so that they will fill out the width of the respective groove completely and will lie against the bottom along its entire extension and against the respective bottom radius.The opposite sides of the O-rings 17 and 18 directed towards the sealing ring 15 and the blade flange 2 respectively, are pressed to a flat form following the planes of the respective surface. Thus, the rings are expanding each one in its respective groove in two opposite directions and an adjusted distribution of the expanding is provided by means of the floating arrangement of the rings, which occupy a position depending of the spring forces arising in connection with the compression of the rings. The choice of material for the second embodiment (Figure 3) can be the same as for the first embodiment. In connection with both embodiments the sealing means is well enclosed and thereby protected against attacks of cavitation.

In Figure 4 the reference numbers are the same for parts which have the same function, as mentioned in the foregoing. Thus are shown a blade flange 2, a pivot 3, a bearing means 4, which by this embodiment comprises two bushings and a propeller hub 1. In addition there is a sealing arrangement 5, which in the embodiment according to figure 4 is very simple in design and includes an O-ring 22 situated in a groove 23 in the propeller hub 1 and sealing against a surface 24 of the propeller blade flange 2. The groove 23 with respect to its width and bottom radii is dimensioned in such a manner relative to the dimensions of the O-ring 22 when it is pressed against the surface 24 that the ring gets a full fit to the bottom and radii of the groove 23. By this arrangement the O-ring is locked in the groove by friction forces.In the embodiment according to figure 4 the measure for the radii of the groove 23 corresponds to one half of the width of the groove and to approximately one half of its depth, whereby the O-ring 19 rests substantially only against rounded surfaces of the groove and also against limited parts of its straight sides.

In the embodiment according to Figure 2 a considerable friction arises between the O-ring 10 and its resting surfaces compared to the friction between the sealing ring 11 of bronze and the blade flange 2 as a result of the hard compression of the O-ring and the large resting surfaces at the bottom 9 of the groove and at the sealing ring 11. Hereby movement is prevented in relation to the O-ring 10, in other words, the sealing ring 11 is locked relative to the supporting ring 7, held by the propeller hub, and all sliding movements will occur between the sealing ring 11 and the blade flange 2. By a suitable choice of material the wear can substantially be limited to the sealing ring 11, which can easily be exchanged. Any wear of the O-ring or risk of twisting with a resulting leakage and possibly uneven wear can not arise, as the O-ring works as a stationary seal.

A possible wear of the blade flange can also easily be repaired.

In the embodiment according to figure 3, the O-rings 17 and 18 because of the trilateral bearing will be securely locked in their grooves and cannot perform any twisting movement. Neither can any relative movement between the rings and the grooves occur, and thus, no wear can result in the grooves, which are comparatively difficult to machine. Because of the fact that the O-ring 17 is larger than the O-ring 18 a harder compression and larger bearing surfaces will occur with the first mentioned O-ring this resulting in the sealing ring 15 being locked in relation to the supporting ring 12 held by the hub. Thus, the sliding takes place between the sealing ring 15 and the blade flange 2 and the function of the O-ring 18 is to compensate minor unevenesses and damage in order to maintain the sealing capacity.If as an exceptional case it should happen that sliding takes place between the sealing ring 15 and the O-ring 17, a locking of the O-rings 17 and 18 in their grooves is in any case secured, so that the risk of twisting of the rings and wear of the walls of the grooves is eliminated.

In the embodiments according to Figures 2 and 3 the supporting rings 7 and 12 respectively are not pivoted in relation to the propeller hub, and therefore the rings 8 and 10 respectively function as stationary seals.

In the embodiment according to Figure 4 the sealing occurs where the O-ring 22 rests against the surface 24, this being displaced relative to the O-ring 22, when the propeller blade 2 pivots relative to the propeller hub 1. As a result of the shape of the groove in accordance to the invention, the O-ring 19 will not move in the groove 20, so that the risk of twisting of the ring and wear in the groove is eliminated. In the arrangement according to Figure 4 it is very important that damage from wear in the propeller hub 1 is avoided, as such damage due to the necessity of undertaking an extensive dismantling work is very difficult to repair. On the other hand an adjustment of the surface 24 can easily be made after demounting the respective propeller blade 2.

In the foregoing it has been shown that contrary to what has previously been assumed the combined qualities of certain types of seals can be improved by dimensioning the present O-ring grooves so that the ring is locked therein.

WHAT WE CLAIM IS: 1. A sealing arrangement between parts which are arranged to rotate relative to each other with one part provided with a groove which partly encloses an O-ring of resilient material which in an uncompressed condition is of substantially circular cross-section, a surface on the other part pressing against the O-ring so that the O-ring is deformed and forms a seal between the groove and said surface, the surface of the groove being at least in part curved in transverse crosssection, the curvature of the groove surface and the resilient properties of the O-ring being selected so that the O-ring in the compressed condition rests against the major part of the surface of the groove along an unbroken line as seen in transverse crosssection and the length of the O-ring surface, as viewed in transverse cross-section, which engages said other part is less than the length of the O-ring surface, as viewed in transverse cross-section, engaging the surface of the groove, whereby the O-ring is fixed in position in the groove but movable in relation to the surface of said other part.

2. A sealing arrangement as claimed in claim 1, in which the bottom of the groove is connected to two opposing sides of the groove by radii which correspond approximately to one half of the depth of the groove, and the groove has a width corresponding to the width of the deformed O-ring so that the same extends the full distance between the sides of the groove.

3. A sealing arrangement as claimed in claim 1 or 2, in which said surfaces of said parts face each other.

4. A sealing arrangement as claimed in claim 1, 2 or 3, in which said other part is in the form of a sealing element having an additional surface which is pressed by the deformed O-ring against a further surface producing a seal between the sealing element and said further surface.

5. A sealing arrangement as claimed in claim 4, in which the sealing element has a grooove in the additional surface, which groove is arranged to accomodate an additional O-ring which is pressed by said deformed O-ring against said further surface, 6. A sealing arrangement between a portion of a shaft and a bearing means in which the portion of the shaft is rotatable, comprising a body rigidly connected to the bearing means and provided with a surface in which an annular groove is made, an O-ring of resilient material and in uncompressed condition of substantially circular cross-section, being located in the groove and engaged by a first flat radially extending surface of a second ring of a non-resilient material located in a position between the O-ring and a flat radially extending surface belonging to the portion of the shaft, with a second flat radially extending surface of the second ring which is opposed to said first flat radially extending surface, bearing against the flat radially extending surface belonging to the portion of the shaft, the surface of the groove being at least in part curved in transverse cross-section, the curvature of the groove surface and the resilient properties of the O-ring being selected so that the O-ring in the compressed condition rests against the major part of the surface of the groove along an unbroken line as seen in transverse cross-section, and is pressed against said first flat radially extending surface of the said second ring, the length of the O-ring surface, as viewed in transverse cross-section, which engages said first flat radially extending surface being less than the length of the O-ring surface, as viewed in transverse cross-section, engaging the surface of the groove, whereby the 0-ring is fixed in position in the groove.

7. A sealing arrangement between parts which are arranged to rotate relative to each other, constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. seals. In the embodiment according to Figure 4 the sealing occurs where the O-ring 22 rests against the surface 24, this being displaced relative to the O-ring 22, when the propeller blade 2 pivots relative to the propeller hub 1. As a result of the shape of the groove in accordance to the invention, the O-ring 19 will not move in the groove 20, so that the risk of twisting of the ring and wear in the groove is eliminated. In the arrangement according to Figure 4 it is very important that damage from wear in the propeller hub 1 is avoided, as such damage due to the necessity of undertaking an extensive dismantling work is very difficult to repair. On the other hand an adjustment of the surface 24 can easily be made after demounting the respective propeller blade 2. In the foregoing it has been shown that contrary to what has previously been assumed the combined qualities of certain types of seals can be improved by dimensioning the present O-ring grooves so that the ring is locked therein. WHAT WE CLAIM IS:

1. A sealing arrangement between parts which are arranged to rotate relative to each other with one part provided with a groove which partly encloses an O-ring of resilient material which in an uncompressed condition is of substantially circular cross-section, a surface on the other part pressing against the O-ring so that the O-ring is deformed and forms a seal between the groove and said surface, the surface of the groove being at least in part curved in transverse crosssection, the curvature of the groove surface and the resilient properties of the O-ring being selected so that the O-ring in the compressed condition rests against the major part of the surface of the groove along an unbroken line as seen in transverse crosssection and the length of the O-ring surface, as viewed in transverse cross-section, which engages said other part is less than the length of the O-ring surface, as viewed in transverse cross-section, engaging the surface of the groove, whereby the O-ring is fixed in position in the groove but movable in relation to the surface of said other part.

5. A sealing arrangement as claimed in claim 4, in which the sealing element has a grooove in the additional surface, which groove is arranged to accomodate an additional O-ring which is pressed by said deformed O-ring against said further surface,

6. A sealing arrangement between a portion of a shaft and a bearing means in which the portion of the shaft is rotatable, comprising a body rigidly connected to the bearing means and provided with a surface in which an annular groove is made, an O-ring of resilient material and in uncompressed condition of substantially circular cross-section, being located in the groove and engaged by a first flat radially extending surface of a second ring of a non-resilient material located in a position between the O-ring and a flat radially extending surface belonging to the portion of the shaft, with a second flat radially extending surface of the second ring which is opposed to said first flat radially extending surface, bearing against the flat radially extending surface belonging to the portion of the shaft, the surface of the groove being at least in part curved in transverse cross-section, the curvature of the groove surface and the resilient properties of the O-ring being selected so that the O-ring in the compressed condition rests against the major part of the surface of the groove along an unbroken line as seen in transverse cross-section, and is pressed against said first flat radially extending surface of the said second ring, the length of the O-ring surface, as viewed in transverse cross-section, which engages said first flat radially extending surface being less than the length of the O-ring surface, as viewed in transverse cross-section, engaging the surface of the groove, whereby the 0-ring is fixed in position in the groove.