The invention relates to a seal for sealing a material transfer apparatus. The material is usually a powder, pellets or a similar flowable material.

In the transport, storage and general handling of flowable material such as powder, particulate material, granules and the like, it is nowadays usual for such materials to be held in bins, containers, hoppers, silos, or intermediate bulk containers (I.B.C’s). Such containers have a filling inlet and a discharge outlet. The outlet is often of hopper configuration, and is usually obturated by a closure device which is substantially conical or frusto-conical. The cone in the obturating position rests on the inner (in use) surface of the outlet hopper. At a discharge or transfer station, the closure device is raised from the hopper outlet by suitable means, such as a bellows device marketed under the registered trade mark MATCON®, to open an annular discharge opening between the hopper outlet and the closure device through which a desired amount of the flowable material can pass to other stations for use.

The material transfer apparatus may comprise a cone valve. In this case, there is a need to seal the cone valve. When a seal is fitted to the apparatus, over time, the seal typically becomes worn or damaged such that there is a need to replace the seal. Such replacement of the seal can be expensive and may result in a significant period of down time of the apparatus which can be detrimental to production. In some industries where maintaining good hygiene is not a high priority, some users choose not to maintain worn or damaged cone seals in order to avoid the cost and down time that would be required when replacing the seal. This often leads to poor cone seal performance, powder leakage and hence a dusty factory environment.

Past attempts at developing a removable cone seal have included use of the standard “C” section bonded cone seal that is fitted around the cone valve seal ring but without sealant or adhesive. This has tended to work acceptably well for a short time but over time the ingress of powder occurs behind the seal cavity due to the pressure and/ or vacuum effects of repeated valve opening and closing. This powder ingress could lead to cross-contamination between powder batches, or distortion of a blend recipe as some ingredients may be excluded from the batch.

The present invention aims to address the above problems. According to a first aspect, there is provided a seal for use in sealing a movable closure in an aperture of a material transfer and/ or containment device, the seal comprising a first seal surface configured to cooperate with a corresponding surface of the aperture and a second seal surface configured to cooperate with a corresponding seal seat of the closure, wherein the seal is dimensioned relative to the seal seat such that the seal material requires compression for retention thereby, the seal comprising a closed cell porous core and an outer layer adapted to prevent powder ingress.

Advantageously, the seal is hygienic in design and reduces cross-contamination between different powder batches. This is a particular advantage in the pharmaceutical industry, and especially where automated repeatable IBC washing is a requirement.

Typically, the seal is prepared by an extrusion process. Preferably, the seal comprises a silicone material. Preferably, the seal comprises a sponge. Typically, the sponge comprises a closed cell porous core.

It is preferred that the seal has a density of between 400 and 800 kg/m ³ . Preferably, the seal has a density of 600 kg/m ³ .

In a preferred embodiment, the seal comprises a material that is FDA approved and is compliant to FDA-CFR 21 Part.1772600.

Preferably, the seal is weather resistant, UV resistant, ozone resistant and has good aging proof.

Advantageously, the seal has a sealing performance which provides good sealing quality as well as the benefits of convenience and reduced cost and down-time.

Preferably, the seal requires slight compression to enable it to be assembled with the cone valve. Advantageously, such compression helps prevent powder ingress into the seal joints above and below the seal, thus reducing the required frequency of cleaning.

According to a second aspect, there is provided a valve for obturating the outlet of a material discharge apparatus for discharging flowable particulate material, the apparatus including an outlet hopper, the valve comprising a conical or frustoconical closure device seated, in the closed position, on an inner, in use, surface of the outlet hopper and raisable internally within the hopper to open an annular discharge opening between the hopper and the closure device, the closure device including a seal seat dimensioned to receive and removably retain a seal by compression of the seal alone, and a compressible seal according to the first aspect described above.

According to a third aspect, there is provided a method of sealing a valve comprising the use of a seal according to the first aspect.

The invention will be further described by way of example and with reference to the following figures, in which:

Figure la shows a partial side view of the seal of the present invention;

Figure lb shows a partial side view of a prior art seal;

Figure 2a shows a top plan view of the seal of the present invention;

Figure 2b shows a side section view of the seal of the present invention;

Figure 2c shows an enlarged partial side view of the seal of the present invention showing the detail from Section A shown in Figure 2b; and

Figure 2d shows a front perspective view of the seal of the present invention.

With reference to Figure 2a, there is provided a seal (2) for use in sealing a movable closure in an aperture of a material transfer and/ or containment device, the seal comprising a first seal surface configured to cooperate with a corresponding surface of the aperture and a second seal surface configured to cooperate with a corresponding seal seat of the closure, wherein the seal is dimensioned relative to the seal seat such that the seal material requires compression for retention thereby, the seal comprising a closed cell porous core and an outer layer adapted to prevent powder ingress. Advantageously, the seal is prepared by an extrusion process which creates a sponge profile with an outer skin which is useful in preventing powder ingress into the pores of the sponge. Advantageously, the seal (2) is closed cell in nature so that no power can pass between the pores even in the event that ingress did occur.

The seal comprises a silicone material having a density of around 600 kg/m ³ .

The typical property data for the material used to form the seal is set out in Table 1 below:

Table 1

Post cure 200°C / 4 hours Curing system: Addition cured

The material that is used to form the seal advantageously has good ageing proof, very good ozone resistance, very good weather resistance and very good UV resistance.

The material that is used to form the seal is FDA approved and is compliant to FDA-CFR 21 Part.1772600, or FDA 21 CFR 177.2600.

Typically, sponges could not previously be used for direct food and pharmaceutical powder contact because the gasses used in the manufacturing process for expanding the sponge were considered toxic. When FDA approved sponges were initially offered to market they were much too dense to provide the softness needed to perform as a cone seal. These issues have advantageously been overcome using the seal of the present invention which comprises a sponge having a structure such that no powder could pass between the pores of the sponge even if ingress did occur.

The seal (2) is typically designed such that it has an “interference fit” with respect to the cone valve, i.e. the profile of the seal is dimensioned such that it is slightly larger than the cone valve to which it is fitted. The seal (2) requires slight compression to enable it to be assembled. Advantageously, this compression helps prevent powder ingress into the seal joints above and below the seal, thus reducing the required frequency of cleaning.

With reference to Figures la and lb, the seal has an outer profile that is similar to a standard bonded seal. Advantageously, the seal of the present invention has a sealing performance which provides good sealing quality and provides the benefits of convenience and reduced cost and down-time.

With reference to the figures, there is also provided a valve for a material discharge apparatus comprising a seal (2) for use in sealing a movable closure in an aperture of a material transfer and/ or containment device, the seal comprising a first seal surface configured to cooperate with a corresponding surface of the aperture and a second seal surface configured to cooperate with a corresponding seal seat of the closure, wherein the seal is dimensioned relative to the seal seat such that the seal material requires compression for retention thereby, the seal comprising a closed cell porous core and an outer layer adapted to prevent powder ingress.

With reference to the figures, there is also provided a method of sealing a valve comprising the use of a seal (2) for use in sealing a movable closure in an aperture of a material transfer and/ or containment device, the seal comprising a first seal surface configured to cooperate with a corresponding surface of the aperture and a second seal surface configured to cooperate with a corresponding seal seat of the closure, wherein the seal is dimensioned relative to the seal seat such that the seal material requires compression for retention thereby, the seal comprising a closed cell porous core and an outer layer adapted to prevent powder ingress.

In manufacture, the seal is prepared by an extrusion process and comprises a closed cell porous core and an outer layer adapted to prevent powder ingress. In use, the seal is removably fitted to a sealing ring of a cone valve. The seal requires slight compression to enable it to be assembled with the cone valve. Advantageously, this compression helps prevent powder ingress into the seal joints above and below the seal, thus reducing the required frequency of cleaning.