Patent Description:
The seals of rotary feeders undergo significant wear and tear, especially when feeding abrasive materials. This requires them to be replaced often. For this purpose, installation holes are arranged in the face flanges of the body of the rotary feeder, being closed up during operation. The dimensions of the installation holes are large enough for a hand to be inserted with appropriate tools to release the seal and then pull it out. A new seal is then mounted in a reverse order. <CIT> discloses a system for securing the seal to the blade, based on the fact that the seal is screwed in place with the aid of force-locking screws. The mounting technique involves inserting a new seal via one of the installation holes into the internal space of the rotary feeder and fixing the two-part seal with a strip with force-locking screws. These screws are passed through positioning holes and screwed into anchor holes made in the blade.

This is inconvenient work, since it takes place in a tight space. Besides this drawback of the known fastening system, a precise alignment of the seal with the body is difficult to achieve and depends on the touch and manual dexterity of the worker performing the installation. The inaccuracy is caused in the clearance required from the seal, during its positioning. The seal is guided only by the force-locking screws.

In an improved version of this fastening system, the seal is centred by means of pins and then secured by the force-locking screws. While the precision of positioning the seal is greater in this version, the inconvenience involved in its replacement still remains. In addition, <CIT> and <CIT> describe rotary feeders for bulk material with a main housing, a rotor disposed within a cylindrical passage of the main housing and adapted to rotate therein. The rotor including angularly-spaced radially-extending rotor blades, each of said rotor blades having a sealing tip assembly secured to its outer edge and extending transversely the full width of the rotor pocket and extending radially into sealing engagement with the cylindrical passage of the main housing. More particularly, <CIT> discloses a system of fastening a seal to a rotor blade of a rotary feeder of loose material, comprising said seal and said rotor blade, wherein the seal secured to the blade has a sealing edge arranged above the top edge of the blade, wherein- below the top edge, a groove is formed in the wall of the blade which is parallel with the axis of the rotor, said system comprising:.

Further <CIT> shows a rotary feeder with conveyor blades and reinforcing strips which are located in the free end of the conveyor blades and form a cutting edge of the conveyor blade. Each conveyor blade as a longitudinal groove with a corresponding recess for positive reception of the reinforcing strips.

It is therefore an object of the invention to significantly reduce the drawbacks of a system of fastening a seal to a rotor blade of a rotary feeder.

In an exemplary embodiment a system is provided that includes a hard seal of abrasion-resistant material or a soft seal of nonabrasive material, against which a supporting strip is pressed in the direction of the blade. The seal secured to the blade has a sealing edge located above the top edge of the blade. According to the invention, below the top edge of the blade, a groove is formed in the wall of the rotor blade. The groove is substantially parallel with the axis of the rotor. The supporting strip is inserted into the groove by sliding. The shape of the supporting strip's first contact surface basically matches the shape of the groove. The rear side of the supporting strip is provided with a second contact surface, against which a contact surface of the seal rests. According to the invention, at both ends of the groove there are formed at least two anchor holes in the rotor blade, which are adapted to the fastening of securing screws. Through holes are made in the supporting strip, which are concentric with the anchor holes when the support strip is fully inserted into the groove. Through holes are formed in the seal, too, which fits to the anchor holes in the blade and the through holes in the supporting strip. On the side opposite the contact surface the seal's through holes are provided with a conical recess with a similar conicity as the conical heads of the securing screws. When the supporting strip with the seal is inserted into the groove and the securing screws are tightened, a rigid unit is formed by the seal and blade.

The benefit of the indicated arrangement is that the seal may be easily pushed into the blade by means of the groove and then fixed to the blade by means of the securing screws. Another benefit is the accurate fit of the seal in the blade, thus precisely limiting its position relative to the body of the rotary feeder.

In an advantageous embodiment, the groove has a concave shape or the shape of a dovetail. In the radial direction from the axis of the rotor to the back side of the blade the groove has an oblique bottom surface, pointing radially inward towards the centre or axis of the rotor at a slant from the wall of the blade. A bottom surface parallel to the blade surface adjoins the oblique bottom surface at least up to the area beneath the anchor holes. Above the anchor holes there is formed an oblique top surface with opposite inclination to that of the oblique bottom surface. The oblique top surface is adjoined at an acute angle by a normal top surface, which is parallel to the normal bottom surface.

In such a groove, the strain is transmitted from the seal to the blade by the groove based on an interlocking form of the seal, supporting strip and the groove. Therefore only two securing screws are sufficient for fastening the seal to the blade, one at either end of the seal. This significantly facilitates the installation of the seal.

An easier fabrication of the blade with the groove is made possible by a modification in which the normal bottom surface is in the same plane as the normal top surface.

Depending on the properties of the bulk material, forces are transmitted from the seal to the blade which, if secured by only two securing screws, might in some instances result in its deformation. According to the invention, in order to increase the rigidity of the seal, threaded holes are arranged in the supporting strip for fastening screws. For these fastening screws, installation holes are arranged in the seal that are provided with a conical recess having a similar conicity as the conical bevelled heads of the fastening screws. The length of the fastening screws is less than the total thickness of the seal and the supporting strip together. Besides assisting in the transfer of force from the seal to the blade, this modification has the advantage that a single part may be formed from the seal and supporting strip, outside the interior of the rotary feeder, which is secured to the blade in the above described manner.

If the seal is formed as a hard seal, a modification can be used for its precise fitting relative to the supporting strip, wherein the seal is provided with a nose in the radial direction from the axis of the rotor. The bearing surface of the nose of the supporting strip rests against a tangential surface of the supporting strip in relation to the axis of the rotor.

In order to press this seal against the supporting strip and the supporting strip against the corresponding surfaces of the groove, the distance of the axis of the conical recess from the bearing surface is less than the distance of the axis of the through hole from the tangential surface. The two axis can have a first eccentricity amounting to <NUM> to <NUM>% of the diameter of the securing screw.

A similar effect may be accomplished when mounting a hard seal on a supporting strip arranged separately outside the interior of the rotary feeder. For this purpose, the distance of the axis of the conical recess from the bearing surface is less than the distance of the axis of the threaded hole from the tangential surface. The two axis can have a second eccentricity amounting to <NUM> to <NUM>% of the diameter of the fastening screw.

In order to increase the effect of the latter mentioned modifications, the dimensions of the conical recess for the securing screws are the same as those of the conical recess for the fastening screws. Moreover, the dimensions of the conical heads of the securing screws are the same as those of the conical bevelled heads of the fastening screws. At the same time, the first eccentricity dictated by the distance of the axis of the conical recess for the securing screws from the bearing surface is the same as the second eccentricity dictated by the distance of the axis of the conical recess for the fastening screws from the bearing surface.

The fastening system according to the invention, both in its basic embodiment and in its improving modifications, significantly improves the replacement of the seals of rotary feeders of bulk material.

The enclosed drawing shows schematically the system for fastening a seal to a rotor blade of a rotary feeder according to the invention, where:.

The rotary feeder (<FIG>) comprises a body or housing <NUM>, in which a rotor <NUM> is rotary mounted. The drive mechanism of the rotor is not shown. The rotor <NUM> comprises blades <NUM>, which carry the bulk material upon rotation from an inlet opening <NUM> to an outlet opening <NUM>. The rotor <NUM> is sealed off against the housing <NUM> by seals <NUM>, which are fastened to outer margins of the blades <NUM>. The seals <NUM> have a sealing edge <NUM> located above the top edge <NUM> of the blade <NUM>. At the face flanges of the housing <NUM> insertion openings <NUM> are arranged, which serve for replacing the seal <NUM>. During the operation of the rotary feeder, the insertion openings <NUM> are closed by covers <NUM>.

The seal <NUM> is formed by an element from the group comprising on the one hand a hard seal <NUM> of abrasion-resistant material and on the other hand a soft seal <NUM> of nonabrasive material. For abrasive bulk materials, it is advisable to use abrasion-resistant steel to provide the hard seal <NUM>. For other bulk materials soft seals <NUM>, as made of rubberized textile are sufficient. In order to ensure sufficient rigidity, a locating strip <NUM> is attached to the soft seal <NUM> in the way that will be described below.

Beneath the top edge <NUM> of the blades <NUM>, on their back side <NUM>, there is formed a groove <NUM> in their wall <NUM> being parallel with the axis <NUM> of the rotor <NUM>. The groove <NUM> may have a concave cross section. In an advantageous embodiment (<FIG>, <FIG>), the groove <NUM> has two-tiered dovetail shape. The the two-tiered dovetail comprises, in the radial direction from the axis <NUM> of the rotor <NUM> to the backside <NUM> of the blade <NUM>, an oblique bottom surface <NUM> pointing radially inward from the blade <NUM> in relation to the axis <NUM>. The oblique bottom surface <NUM> is adjoined at least as far as the area beneath the anchor holes <NUM> by a normal bottom surface <NUM>. Above the anchor holes <NUM> there is formed an oblique top surface <NUM> with the opposite inclination to that of the oblique bottom surface <NUM>. The oblique top surface <NUM> is adjoined at an acute angle by a normal top surface <NUM>, which is parallel with the normal bottom surface <NUM>. In the example of <FIG> and <FIG>, the normal bottom surface <NUM> is in the same plane as the normal top surface <NUM>. In this way, there is formed in the groove <NUM> a pocket <NUM>. In an alternative not shown, the groove has a dovetail shape. This means that the normal bottom surface <NUM> may be adjoining the oblique top surface <NUM>, so that there is no additional pocket <NUM> formed.

In the fastening system, a support strip <NUM> is inserted by sliding it into the groove <NUM>. The support strip <NUM> has on its first contact surface <NUM> in direction towards the rotor blades <NUM> a protruding channel which fits substantially to the shape of the groove <NUM>. The rear side of the supporting strip <NUM> is provided with a second contact surface <NUM>, against which rests the contact surface <NUM> of the seal <NUM>.

At each end of the groove <NUM> there is formed in the blade <NUM> at least one anchor hole <NUM> adapted to adjust the securing screws <NUM> (<FIG>, <FIG>). Therefore the anchor holes <NUM> are provided with threads. Another option for the fastening the securing screws <NUM> involves the use of nuts. Through holes <NUM> are arranged in the supporting strip <NUM>, which are concentric with the anchor holes <NUM> when the supporting strip <NUM> is fully inserted into the groove <NUM>. The seal <NUM>, whether made as a hard seal <NUM> or as an soft seal <NUM> and locating strip <NUM>, is provided with locating holes <NUM> with an arrangement similar to that of the anchor and through holes <NUM>, <NUM>.

On the side opposite the seal's <NUM> second contact surface <NUM> the locating holes <NUM> are provided with a conical recess <NUM> with a similar conicity to that of the conical heads <NUM> of the securing screws <NUM> (<FIG>, <FIG>).

Further, threaded holes <NUM> are arranged in the supporting strip <NUM> for fastening screws <NUM>, for which installation holes <NUM> are produced in the seal <NUM> and provided with a conical recess <NUM>. The conical recess <NUM> has a similar conicity to that of the conical bevelled heads <NUM> of the fastening screws <NUM>. The length m of the fastening screws <NUM> is less than the total h of the thickness of the seal <NUM> and supporting strip <NUM> (<FIG>, <FIG>).

The embodiment described thus far pertains to both a seal <NUM> made of hard seal <NUM> and a seal <NUM> containing a soft seal <NUM>. In the event that the seal <NUM> is formed by a hard seal <NUM>, which is illustrated in one advantageous embodiment in <FIG>, it is provided with a nose <NUM> with bearing surface <NUM> in the same plane as the top edge <NUM> of the rotor blade <NUM> nad/or the tangential surface <NUM> of the supporting strip <NUM>. The bearing surface <NUM> rests against the tangential surface <NUM> formed on the supporting strip <NUM> in the relation to the axis <NUM> of the rotor <NUM>.

In the application of a seal <NUM> containing a soft seal <NUM>, the axis <NUM> of the anchor hole <NUM> is identical to the axis <NUM> of the conical recess <NUM> and to the axis <NUM> of the through hole <NUM> (<FIG>). In the application of the seal <NUM> made of a hard seal <NUM>, a similar embodiment can be employed, but it is more advantageous to depart from this identity of the axes (<FIG>) in that the distance g of the axis <NUM> of the conical recess <NUM> from the bearing surface <NUM> is less than the distance b of the axis <NUM> of the through hole <NUM> from the tangential surface <NUM> by a first eccentricity e amounting to <NUM> to <NUM>% of the diameter D of the securing screw <NUM>.

The fastening of the seal <NUM> to the supporting strip <NUM> is arranged in similar manner. When using a seal <NUM> with a soft seal <NUM>, the axis <NUM> of the threaded hole <NUM> is identical to the axis <NUM> of the conical recess <NUM> (<FIG>). If a hard seal <NUM> is used, resting by its nose <NUM> against the tangential surface <NUM> of the blade <NUM>, it is advisable for the distance n of the axis <NUM> of the conical recess <NUM> from the bearing surface <NUM> to be less than the distance c of the axis <NUM> of the threaded hole <NUM> from the tangential surface <NUM> by a second eccentricity f amounting to <NUM> to <NUM>% of the diameter d of the fastening screw <NUM> (<FIG>).

For the transfer of forces, it is advantageous when the dimensions of the conical recess <NUM> for the securing screws <NUM> are the same as those of the conical recess <NUM> for the fastening screws <NUM>, and the dimensions of the conical heads <NUM> of the securing screws <NUM> are the same as those of the conical bevelled heads <NUM> of the fastening screws <NUM>. In this case, the first eccentricity e is the same as the second eccentricity f.

According to the invention, when replacing the seal <NUM>, first of all the cover <NUM> is removed from the housing <NUM> and the blade <NUM> is turned toward the insertion opening <NUM>. After this, the securing screws <NUM> are loosened on each end of the seal <NUM> and the seal <NUM> with the supporting strip <NUM> are removed from the groove <NUM>. The seal <NUM> is released from the supporting strip <NUM> by unscrewing the fastening screws <NUM>.

According to the invention, when mounting a new seal <NUM>, at first a rigid unit is produced, consisting of the supporting strip <NUM> and either a hard seal <NUM>, or an soft seal <NUM> attached by a locating strip <NUM>. To produce this rigid unit, fastening screws <NUM> (<FIG>) are passed through installation openings <NUM> and screwed into threaded holes <NUM> in the supporting strip <NUM>. If the seal <NUM> comprises a hard seal <NUM> with a nose <NUM> and if it contains a conical recess <NUM> shifted by the second eccentricity f with respect to the axis <NUM> of the threaded hole <NUM> (<FIG>), after the tightening of the fastening screws <NUM> the bearing surface <NUM> of the nose <NUM> is pressed against the tangential surface <NUM> of the supporting strip <NUM>.

If the seal <NUM> doesn't comprise a hard seal <NUM> having an eccentric displacement of the conical recess <NUM> of the installation opening <NUM>, or in the event of a seal <NUM> comprising a soft seal <NUM> and a locating strip <NUM>, the self-locating effects are limited to the pressure from the tightened fastening screws <NUM> to the supporting strip <NUM>.

After assembling the rigid unit made of seal <NUM> and supporting strip <NUM>, it is inserted by the insertion opening <NUM> into the groove <NUM> in the blade <NUM> of the rotor <NUM>. The securing screws <NUM> are passed through the locating holes <NUM> in the seal <NUM> and the through holes <NUM> in the strip <NUM> and are screwed into the anchor holes <NUM> in the blade <NUM>. If in a seal <NUM> made from a hard seal <NUM> the conical recess <NUM> is offset by the first eccentricity e, the tightening of the securing screws <NUM> on the one hand ensures the connection between seal <NUM> and supporting strip <NUM> and on the other hand the supporting strip <NUM> is pressed not only against the normal bottom and top surfaces <NUM>, <NUM>, but also against the oblique bottom surface <NUM>. This configuration is important both to assure a precise position of the seal <NUM> and a reliable transfer of forces during the operation in both directions of turning of the rotor <NUM>.

If the seal <NUM> does not have an eccentrically displaced conical recess <NUM>, the force effects are similar to those in the case of no displacement of the conical recess <NUM> of the installation opening <NUM>.

After mounting the seal <NUM>, the cover <NUM> is secured to the housing <NUM> and the rotary feeder is ready to operate.

Claim 1:
System of fastening a seal (<NUM>) to a rotor blade (<NUM>) of a rotary feeder of loose material, comprising said seal (<NUM>) and said rotor blade (<NUM>),
wherein the seal (<NUM>) secured to the blade (<NUM>) has a sealing edge (<NUM>) arranged above the top edge (<NUM>) of the blade (<NUM>),
- wherein below the top edge (<NUM>), a groove (<NUM>) is formed in the wall (<NUM>) of the blade (<NUM>) which is parallel with the axis (<NUM>) of the rotor (<NUM>),
said system comprising
- a supporting strip (<NUM>) being removingly secured in the groove (<NUM>),
- a first rigid unit, produced when mounting said seal (<NUM>), consisting of the supporting strip (<NUM>) and either a hard seal (<NUM>), or a soft seal (<NUM>) attached by a locating strip (<NUM>), said first rigid unit being produced by means of fastening screws (<NUM>) passed through installation openings (<NUM>) of said seal (<NUM>) and screwed into threaded holes (<NUM>) in the supporting strip (<NUM>),
and wherein
- the supporting strip (<NUM>) has a first contact surface (<NUM>) which shape basically matches with the shape of the groove (<NUM>) and a second contact surface (<NUM>) is directly in contact with a contact surface (<NUM>) of the seal (<NUM>),
- wherein the seal (<NUM>) and the supporting strip (<NUM>) forming another rigid unit with the blade (<NUM>) by being fixed with securing screws (<NUM>),
and on each side of the groove (<NUM>) there is at least one anchor hole (<NUM>) formed in the blade (<NUM>), which is adapted to the securing screws (<NUM>)