SPECIFICATIONRing sealThis invention relates to a ring seal comprising elastic material for sealing a gap between two machine components that are movable relative to each other, so as to seal between two spaces at different pressures, which ring seal can be fitted in a groove in one of the machine components.
Ring seal of this kind are known, in the form of what is referred to as "O-rings", of circular cross-section or of other cross-sectional shapes. Particularly for large machine components and correspondingly large diameter ring seals, considerable displacement or adjusting forces are required to overcome the high level of friction produced by the ring seal. This friction also results in a correspondingly large amount of wear, particularly if dust or granular material gets into the gap between the two machine components, as is regularly the case with slider valves and separators or switching devices used in the pneumatic bulk material conveying art.
It is also already known to use tubular inflatable ring seals in such use situations, which inflatable seals however are expensive and require ancillary units for pressurization and pressure relief.
There is thus a need for a generally improved ring seal of simple construction comparable to an O-ring seal, but which in terms of function has the advantages of an inflatable seal, insofar as it fulfils the requirement that the spaces pr chambers which are to be sealed off relative to each other are brought to the same pressure before the machine components, which are displaceable relative to each other and between which the ring seal is disposed, are moved.
According to the invention there is provided a ring seal for sealing a gap between two machine components that are movable relative to each other so as to seal between two spaces at different pressures, which ring seal can be fitted in a groove in one of the machine components, wherein the ring seal comprises elastic material, is annular in shape and has in a diametrically inwardly facing side surface thereof which, when the seal is in operative association with two machine components defining the gap, is directed towards the higher pressure space, a continuous notch therearound which is approximately V-shaped in cross-section, whose depth is at least equal to half the thickness of the ring seal and which, when the seal and machine components are in operative association as aforesaid, communicates with the higher pressure space.
This construction has the advantage that the reduction in cross-section produced by the notch in the ring seal acts as a hinge-like connection between the inner and outer crosssectional regions of the ring seal on either side of the notch.
Preferably the notch, in operation, communicates with the higher-pressure space by way of a cross-sectional region of reduced thickness of the ring seal. Although the communication between the notch and the higherpressure space could be provided by a suitably stepped groove in one of the two machine components, from the point of view of manufacturing procedure it is substantially easier to provide a reduced thickness crosssectional region on the ring seal.
For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:Figure 1 is a cross-sectional view through a ring seal according to one embodiment of the invention,Figure 2 shows a use of the ring seal of Fig.
1 in a tube-type separator or switch device,Figure 3 shows the detail X of Fig. 2 to an enlarged scale with the ring seal under pressure, andFigure 4 shows the same detail X but with the ring seal in the unpressurized condition.
Referring to Fig. 1, an annular ring seal 1 of the invention comprises elastic material, for example silicone rubber, and is provided in its diametrically inwardly facing side surface 1 a with a continuous notch or groove 2.
Fig. 2 shows a cross-sectional view of a conventional tube-type separator or switch device which comprises a housing 3 and a rotor 4 which is mounted therein. The rotor 4 can be pivoted by way of an adjusting cylinder 5 in such a way that a connecting flange 6 either communicates with a connecting flange 7 in the straight-through flow position or with a connecting flange 8 in the inclined flow position. The gaps between the connecting flanges 6, 7 and 8 and the rotor 4 are sealed off by ring seals such as the ring seal of the invention.
Fig. 3 shows the ring seal 1 in a groove 3a in the housing 3, during a pressure conveying operation through the tube-type separator.
The higher pressure in the interior of a tube duct 9, by way of the V-shaped notch 2 in the ring seal 1, causes the ring seal to bear firmly against the rotor 4 as shown in Fig. 3. The side walls of the notch 2 converge in a direction away from the side surface 1 a.
Fig. 4 shows the same detail during displacement of the tube-type separator which is usually effected in the non-pressurized condition. As the notch 2 is no longer subjected to pressure, the ring seal can contract, under its inherent elasticity, so that it then only bears with a really low pressure against the peripheral surface of the rotor 4. In addition, the region of smallest cross-section of the ring seal 1 acts in the manner of a hinge so that, upon rotary movement of the rotor 4 as indicated by the arrow, the portion of the ring seal 1 which is disposed outside the groove 3a pivots into the position shown; that is to say, it can additionally deflect, whereby the degree of friction is also reduced.
As can be seen from the drawing, the communication between the notch 2 and the space 9 in which the higher pressure obtains is provided by a suitable reduction in the cross-section of the ring seal in its region which is nearer the rotor 4 so that a narrow gap remains between the respective side surface of the ring seal and the oppositely disposed side surface of the groove 3a.
The above-described ring seal can also be used in the same manner for sealing other machine components which are moved relative to each other, such as for example flat or gate-type slide valves and slider-type switching devices. Besides the advantages achieved, namely ad degree of friction which is low in the non-pressurized condition, thus giving a low rate of wear and the need for low adjusting forces, a further advantage of the seal is that the pressure thereof against the respective machine components positively increases with an increasing difference between the pressures which obtain on the two sides of the gap to be sealed off.