GB2068260A

GB2068260A - Selecting grating for granulating mill

Info

Publication number: GB2068260A
Application number: GB8040467A
Authority: GB
Original assignee: PREVIERO Sas
Current assignee: PREVIERO Sas
Priority date: 1980-01-30
Filing date: 1980-12-17
Publication date: 1981-08-12
Also published as: FR2474352A1; ES255240U; JPS615954Y2; GB2068260B; ES255240Y; IT8020628V0; FR2474352B1; BE887288A; ATA6381A; DE3100097A1; JPS56159141U; AT378131B

Abstract

Each bore (2) of the plate (1) forming a selecting grating for a granulating mill houses a replaceable bush (3) having a hardness greater than that of said plate (1). A higher stress resistance and a lower wear are thus obtained and the bushes (3), when worn, may be replaced with new ones without any necessity of replacing the entire grating. Each bush (3) is provided with a cutting edge (6) to facilitate cutting of the material being granulated and each bush (3) may be turned in its bore (2) when the cutting edge (6) becomes locally worn to prolong bush life. <IMAGE>

Description

SPECIFICATION Selecting grating for granulating mill The present invention relates to a selecting grating for granulating mill.

As known, a granulating mill is a machine capable of reducing pieces of material of every kind and shape to the size of small granules. It generally comprises a rotor with horizontal axis, which is rotated inside a stator cavity, which communicates upwards with a supply hopper and is closed downwards by a selecting grating having an arcuate shape.

The rotor is provided with radial blades, which, while the rotor is rotating, cooperate with stationary stator counter blades to cut and crumble gradually the material so much that it is reduced to the size of granules capable of passing through the bores of the selecting grating and thus reaching a collecting chamber located below.

A problem of the presently known granulating mills is represented by the wear of the selecting grating, which is subjected to high stresses and resulting deformations, especially when, as it often occurs, a granule having already reduced transversal size but still exaggerated length has come into a bore of the grating and, while it is in that condition, is struck by a blade of the rotor and strongly subjected to tearing stress against the bore wall. Such a drawback, which occurs particularly with rubber-like products, causes the necessity of periodic substitutions of the grating with consequent expenses.

The object of the present invention is to realize a selecting grating for granulating mill, which is subjected to lower wear and involves, in any case, reduced costs of maintenance.

According to the invention this object is attained by means of a selecting grating, comprising a plate provided with bores, characterized in that each bore houses a replaceable bushing having a hardness greater than that of said plate.

The use of bushings of greater hardness obviously allows a higher stress resistance and, therefore, a lower wear and a longer duration. Moreover, once the bushings have worn, it is not necessary to replace the entire grating, but only the bushings. This obviously results in a very reduced cost of maintenance.

Each bushing is preferably provided with an inner cutting edge at its end which, in the use, is faced to the rotor. Such a cutting edge has the function of facilitating the shearing rupture, instead of the tearing rupture, of the granules already partially inserted in the bores of the grating and, due to its hardness, it wears very slowly, assuring an excellent quality of the product for a long time. As the rotor is always rotated in the same sense and it is always the same half of the cutting edge, which works and, consequently wears, it is also possible to double the duration of the cutting edge and, therefore, of the bushing by rotating at a suitable time the bushing through an angle of 180 . The other half of the cutting edge, which is in perfect conditions, is thus ready to work.

The features of the present invention will be better understood by referring, by way of example, to the accompanying drawings, in which: Figure 1 shows a top plan view, developed in a plane and without any bushings, of a selecting grating according to the invention; Figure 2 shows the grating as provided with bushings, sectioned along the line ll-ll of Fig.

1 and with the bending foreseen for its use; Figure 3 shows a part of said grating in top plan view with respect to Fig. 2; Figure 4 shows the same part of the grating in bottom plan view with respect to Fig. 2.

The selecting grating illustrated in the drawings comprises a metallic plate 1 with distributed circular bores 2, which is developed in a plane in Fig. 1 but is really destined to be employed in a granulating mill with the arcuate shape illustrated in Fig. 2.

In each of said bores there is inserted a replaceable bushing 3, which is held in position by a turned end edge 4 thereof and by a Seeger ring 5, which cooperate with opposite faces of the plate 1. The material of the bushings is chosen in such a way as to provide the same bushings with a hardness and, therefore, a stress resistance much higher than that of the plate 1.

As it may be noted from Fig. 2, the end of each bushing 3 which is faced to the center of curvature of the plate 1 and, in the use, to the rotor of the granulating mill, is provided with a circular inner cavity edge 6, which has the function of making easier the cut, by the rotor blades, of the possible granules of exaggerated length, which are already partially inserted in the axial bores of the bushings 3.

For the replacement of the bushings 3, as well as for their rotation of 180 once the first half of the cutting edge 6 has worn, it is sufficient to remove momentarily the Seeger rings 5.

1. Selecting grating for granulating mill, comprising a plate providing with bores, characterized in that each bore houses a replaceable bushing having a hardness greater than that of said plate.

2. Selecting grating according to claim 1, characterized in that one end of said bushing is provided with an inwardly faced cutting edge.

3. Selecting grating according to claim 1, characterized in that said bushing is releasably held inside said bore by an outwardly turned end edge thereof and by a Seeger ring, both of which cooperate with opposite faces of said

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Selecting grating for granulating mill The present invention relates to a selecting grating for granulating mill. As known, a granulating mill is a machine capable of reducing pieces of material of every kind and shape to the size of small granules. It generally comprises a rotor with horizontal axis, which is rotated inside a stator cavity, which communicates upwards with a supply hopper and is closed downwards by a selecting grating having an arcuate shape. The rotor is provided with radial blades, which, while the rotor is rotating, cooperate with stationary stator counter blades to cut and crumble gradually the material so much that it is reduced to the size of granules capable of passing through the bores of the selecting grating and thus reaching a collecting chamber located below. A problem of the presently known granulating mills is represented by the wear of the selecting grating, which is subjected to high stresses and resulting deformations, especially when, as it often occurs, a granule having already reduced transversal size but still exaggerated length has come into a bore of the grating and, while it is in that condition, is struck by a blade of the rotor and strongly subjected to tearing stress against the bore wall. Such a drawback, which occurs particularly with rubber-like products, causes the necessity of periodic substitutions of the grating with consequent expenses. The object of the present invention is to realize a selecting grating for granulating mill, which is subjected to lower wear and involves, in any case, reduced costs of maintenance. According to the invention this object is attained by means of a selecting grating, comprising a plate provided with bores, characterized in that each bore houses a replaceable bushing having a hardness greater than that of said plate. The use of bushings of greater hardness obviously allows a higher stress resistance and, therefore, a lower wear and a longer duration. Moreover, once the bushings have worn, it is not necessary to replace the entire grating, but only the bushings. This obviously results in a very reduced cost of maintenance. Each bushing is preferably provided with an inner cutting edge at its end which, in the use, is faced to the rotor. Such a cutting edge has the function of facilitating the shearing rupture, instead of the tearing rupture, of the granules already partially inserted in the bores of the grating and, due to its hardness, it wears very slowly, assuring an excellent quality of the product for a long time. As the rotor is always rotated in the same sense and it is always the same half of the cutting edge, which works and, consequently wears, it is also possible to double the duration of the cutting edge and, therefore, of the bushing by rotating at a suitable time the bushing through an angle of 180 . The other half of the cutting edge, which is in perfect conditions, is thus ready to work. The features of the present invention will be better understood by referring, by way of example, to the accompanying drawings, in which: Figure 1 shows a top plan view, developed in a plane and without any bushings, of a selecting grating according to the invention; Figure 2 shows the grating as provided with bushings, sectioned along the line ll-ll of Fig. 1 and with the bending foreseen for its use; Figure 3 shows a part of said grating in top plan view with respect to Fig. 2; Figure 4 shows the same part of the grating in bottom plan view with respect to Fig. 2. The selecting grating illustrated in the drawings comprises a metallic plate 1 with distributed circular bores 2, which is developed in a plane in Fig. 1 but is really destined to be employed in a granulating mill with the arcuate shape illustrated in Fig. 2. In each of said bores there is inserted a replaceable bushing 3, which is held in position by a turned end edge 4 thereof and by a Seeger ring 5, which cooperate with opposite faces of the plate 1. The material of the bushings is chosen in such a way as to provide the same bushings with a hardness and, therefore, a stress resistance much higher than that of the plate 1. As it may be noted from Fig. 2, the end of each bushing 3 which is faced to the center of curvature of the plate 1 and, in the use, to the rotor of the granulating mill, is provided with a circular inner cavity edge 6, which has the function of making easier the cut, by the rotor blades, of the possible granules of exaggerated length, which are already partially inserted in the axial bores of the bushings 3. For the replacement of the bushings 3, as well as for their rotation of 180 once the first half of the cutting edge 6 has worn, it is sufficient to remove momentarily the Seeger rings 5. CLAIMS

3. Selecting grating according to claim 1, characterized in that said bushing is releasably held inside said bore by an outwardly turned end edge thereof and by a Seeger ring, both of which cooperate with opposite faces of said plate.

4. A selecting grating for a granulating mill substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

5. A granulating mill comprising a rotor rotatably mounted with a stator casing, said stator casing comprising a selecting grating in the form of a plate provided with bores, characterised in that each bore houses a replaceable bushing having a hardness greater than that of said plate.

6. A granulating mill according to claim 5, wherein said rotor is provided with at least one radially extending blade.

7. A grating mill according to claim 6, wherein said stator casing is provided with at least one counter blade.

8. A grating mill according to any one of claims 5 to 7, wherein said rotor is mounted so as to be rotatable in use about a substantially horizontal axis.

9. A grating mill according to any one of claims 5 to 8, comprising supply hopper means located above said stator casing and communicating therewith.

10. A grating mill according to any one of claims 5 to 9, comprising a granulated material collecting chamber located beneath said stator casing and communicating therewith through said selecting grating.

11. A grating mill substantially as hereinbefore described comprising a selecting grating substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.