GB2151947A

GB2151947A - Apparatus and a method suitable for grading pieces of granite by size

Info

Publication number: GB2151947A
Application number: GB08334409A
Authority: GB
Inventors: Brian Chang
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-12-23
Filing date: 1983-12-23
Publication date: 1985-07-31
Also published as: GB8334409D0

Abstract

The apparatus comprises a hollow body (1) formed by two end rings (2) interconnected by a plurality of elongate steel bars (3). The steel bars are equi-angularly spaced around the circumference of the cylinder defined thereby and two steel strips (4) are wound in oppositely directed spirals around the steel bars to form a framework. The body (1) is mounted on four drive end support arrangements (6), two arrangements being provided at each end of the body (1). Each arrangement comprises two rollers each rotatably journalled on a support (9). One of the rollers (7) serves to support the body (1) while the other roller (8) is connected by a belt and pulley arrangement (15) to the drive shaft of a respective motor (11). In use of the apparatus, the body (1) is inclined downwardly at about 15 DEG to the horizontal and the uppermost end (1a) thereof is charged with granite pieces. The body (1) is then rotated by the motors (11) and the granite pieces travel slowly along the inner surface of the body (1), so that those pieces having a dimension smaller than the gap between the steel bars (3) fall through the steel bars and collect within the skid (10). The desired larger pieces of granite are collected at the other lower end (1b) of the body (1). <IMAGE>

Description

SPECIFICATION Apparatus and a method suitable for grading pieces of granite by size This invention relates to apparatus and a method suitable for grading pieces of granite by size.

Conventionally, pieces of granite are graded by size on site at the granite quarry using a vibrating sieve or "grissley". There are, however, a number of problems inherent in the conventional vibrating type grissley. Thus, if a vibrating type grissely designed to separate granite pieces having a smallest dimension of not less than 12" (30 cms) is used when placed on a slope, the pieces of granite having a size of 12" (30 cms) and above tend to wedge between the bars of the grissley. It is therefore necessary to stop the operation of the grissley and the wedged pieces of granite can only be removed with great difficulty. Indeed, it may be necessary to use a crane to remove the pieces of granite from between the grissley bars. Further, the impact of the pieces of granite on the bars of the vibrating grissley causes tremendous wear.In extreme cases, some of the bars of the grissley may be torn and broken up in which case it will be necessary to stop the operation so that the bars of the grissley can be repaired or renewed.

It is an object of the present invention to provide apparatus and a method suitable for grading pieces of granite by size which overcome or at least mitigate the above-mentioned problem.

According to one aspect of the present invention, there is provided apparatus suitable for grading pieces of granite by size, comprising a rotatable hollow body for receiving pieces of granite, the surface of the hollow body being formed with one or more apertures of a predetermined size and means for rotating the hollow body so that, when pieces of granite are placed in the hollow body and the body is rotated, pieces of granite smaller than a predetermined minimum size pass through the aperture(s).

In a second aspect, the present invention provides a method for grading pieces of granite by size comprising charging a rotatable hollow body with pieces of granite, the surface of the hollow body having one or more apertures of a predetermined size, and rotating the body so that pieces of granite below a predetermined size pass through the aperture(s).

For a better understanding of the present invention, and to show how the same may be put into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a perspective view of part of apparatus in accordance with the invention; Figure 2 is a schematic plan view of a drive arrangement for the apparatus; Figure 3 is a cross-sectional view of the apparatus of Figure 1 taken along the line Ill-Ill in Figure 1, the drive motors having been omitted from Figure 3; and Figure 4 and 5 show a plan and elevational views, respectively, of a skid of the apparatus.

Referring now to the drawings, there is shown an apparatus suitable for grading pieces of granite by size. The apparatus comprises a cylindrical body 1, the surface of which is formed by a framework of steel bars. As shown in Figure 1, the framework comprises two end rings 2 and a plurality of steel bars 3 extending between the two end rings and equi-angularly spaced about the circumference of the cylinder formed thereby. Each steel bar is preferably of 3" (7.6 cms) x 10" (25.4 cms) in cross-section. The number of bars provided and the diameter of the end rings 2 will determine the size of the duct through which pieces of granite can escape from the drum. The steel bars 3 are held in place by two steel strips 4 wound spirally along the periphery of the hollow body 1.As can be seen from Figure 1, one of the steel strips 4 is wound in a clock-wise direction round the bars 3 while the other steel strip 4 is wound in the anticlockwise direction. A collar 5 surrounds one end 1a of the body 1 and a similar shorter collar 6 surrounds the other end 1b of the body. The collars 5 and 6 serve not only as strength members but also to ensure that pieces of granite having a dimension small enough to pass between the steel bars 3 fall through the body 1 into a desired collecting section beneath the middle portion of the body 1 and do not fall between the bars with end regions of the body 1 where they may interfere with the operation of the apparatus.

The body 1 is supported on a skid or base 10 made of mild steel by four drive support arrangements 6. The skid 10 is shown in detail in the plan view of Figure 4. Figure 5 is an elevational view of the skid 10 showing the body 1 and associated components in dashed lines. Preferably the skid 10 is approximately 25 feet (6.35m) in length and approximately 14 feet (3.56m) in width. Each of the drive and support arrangements 6 is identical and therefore, in interest of clarity, only two of the drive and support arrangements 6 are shown in Figure 1. It should be understood that two drive and support arrangements 6 are provided to support the one end 1a of the body 1 and two other drive and support arrangements 6 are provided to support the other end 1b of the body 1.

Each drive and support arrangement 6 comprises a support roller 7 and a drive roller 8, each roller being mounted on the skid or base rotatably jour nalled to a respective support 9 mounted on the skid or base 10. The rollers 7 and 8 are normally "tyre" type rollers and are each composed of a number of separate tyre-like sections pressed together. The supports 9 are formed of mild steel.

Preferably, the rollers 7 and 8 are formed of rubber, rubber being selected in lieu of steel because of the cushioning effect of the former which provides a better contact with the collars 5 and 6 and therefore results in quieter operation of the apparatus.

Each drive and support arrangement 6 comprises a respective drive motor 11 connected to the shaft carrying the drive roller by a belt pulley arrangement 15. The drive and support arrangement 6 are shown more clearly in Figure 2 which is a sche matic plan view of the drive and support arrangements and their connection to the skid 10. The body 1, support rollers 7 and details of the skid 10 have been omitted from Figure 2 in the interests of clarity.

A respective thrust ring 12 is provided around each of the collars 5 and 6 on the body 1. The thrust rings 12 engage thrust rollers 13 (Figure 3) secured to parts of the base 10 (not shown) by means of plummer blocks 14 in the arrangement shown, two thrust rollers 13a are provided on one side of each thrust ring and one thrust roller 13b on the other side of the thrust ring. The thrust rollers 13 serves to prevent the drum or body 1 from sliding when it is placed on an incline.Although not shown in Figure 3, thrust rollers 13 are arranged in a similar manner at each end 1a and 1b of the body 1 so that, when the body 1 is placed on an incline, the two thrust rollers 13a are downhill of the one thrust roller 13b at each end of the body so that each pair of two thrust rollers 13a shoulders the thrust when the body 1 is installed at, for example, a 15C inclination while the respective one thrust roller 13b prevents the drum climbing uphill during operation.

In the preferred arrangement, the body 1 is of approximately 8 feet (240 cms) in diameter and each of the motors is a 30 horse power motor.

The apparatus is positioned in use at the quarry site at an inclination of'15" to the horizontal so that the end la of the body 1 is higher than the end 1 b.

The body 1 is rotated by the motors 11 at a speed of about 1.6 RPM. and, with the help of the 15 inclination, granite chunks or pieces supplied to the end 1a of the body 1 travel slowly along the body 1. The framework defined by the steel bars 3 and the steel strips 4 is such that granite pieces having no dimensions smaller than 12" (30 cms) travel along the drum while smaller pieces drop through the gaps in the framework and collect within the skid 10. The desired large pieces of granite are collected at the end 1 b of the drum.

The apparatus described eliminates or at least minimizes the possibility of pieces of granite wedging between the bars of the apparatus. Also the amount of wear caused impact of the granite on the bars is minimized.

In use of the apparatus, there has been no evidence that the bars tear or crack under heavy impact load. Also, the apparatus is quieter in operation than the conventional vibrating grissley and is more flexible than the conventional grissley because, if one of the four motors fails, the equipment can still operate satisfactory.

Claims

1. Apparatus suitable for grading pieces of granite y size, comprising a rotatable hollo body for receiving pieces of granite, the surface of the hollow body having one or more apertures of a predetermined size and means for rotating the hollow body so that, when the pieces of granite are placed in the hollow body and the body is rotated, pieces of granite below a predetermined size pass through the aperture(s).

2. Apparatus according to claim 1, wherein the hollow body comprises a cylinder.

3. Apparatus according to claim 2, wherein the surface of the hollow body is defined by a network of eiongate members.

4. Apparatus according to claim 3, wherein at least one end of the cylindrical hollow body gave a portion 3 formed of apertures.

5. Apparatus according to any preceding claims, wherein the rotating means comprises at least one roller contacting the surface of the body and motor means for rotating the roller.

6. Apparatus according to claim 5, when dependent on claim 2, wherein two rollers are provided at each end of the cylindrical hollow body, each roller being rotatable by motor means.

7. Apparatus according to claim 6, wherein each roller is associated wi8th a respective motor for rotating the roller.

8. Apparatus according to claim 6 or 7, wherein a further roller rotatably mounted on a support is associated with each drive roller.

9. Apparatus according to claim 8, wherein each support forms part of a base of the apparatus.

10. Apparatus according to claim 5, 6, 7, 8 or 9 wherein the or each roller is composed of a plurality of tyre-like sections which are pressed together.

11. Apparatus according to any preceding claim, wherein the rotatable hollow body is provided with a thrust ring for engaging one or more thrust rollers connected to a base of the apparaus to prevent the body sliding when the body is placed on an inclined to prevent the body climbing uphill during rotation thereof.

12. A method for grading pieces of granite by size, comprising charging a rotatable hollow body with pieces of granite, the surface of the hollow body having one or more apertures of a predetermined size and rotating the hollow body so that pieces of granite below a predetermined size pass through the aperture(s).

13. A method for grading pieces of granite by size substantially as hereinbefore described with reference to the accompanying drawings.

13. Apparatus suitable for grading pieces of granite by size substantially as hereinbefore described, with reference to, and as illustrated in, the accompanying drawings.

14. A method for grading pieces of granite by size substantially as hereinbefore described with reference to the accompanying drawings.

15. Any novel feature or combination of features described herein.

New claims fiied on 4th July 1984 Superseded claims 1 to 15 New of amended claims: CLAIMS

1. Apparatus suitable for grading pieces of granite by size, comprising a rotatable hollow body for receiving pieces of granite, the surface of the hollow body having one or more apertures of a predetermined size and rotating means comprising at least one roller contacting the surface of the body and motor means for rotating the roller to rotate the hollow body so that. when the pieces of granite are placed in the hollow body and the body is rotated, pieces of granite below a predetermined size pass through the aperture(s).

3. Apparatus according to claim 2, wherein the surface of the hollow body is defined by a network of elongate members.

4. Apparatus according to claim 3, wherein at least one end of the cylindrical hollow body has a portion free of apertures.

5. Apparatus according to claim 2, 3 or 4, wherein the two rollers are provided at each end of the cylindrical hollow body, each roller being rotatable by motor means.

6. Apparatus according to claim 5, wherein each roller is associated with a respective motor for rotating the roller.

7. Apparatus according to claim 5 or 6, wherein a further roller rotatably mounted on a support is assiciated with each drive roller.

8. Apparatus according to claim 7, wherein each support forms part of a base of the apparatus.

9. Apparatus according to any preceding claim, wherein the or each roller is composed of a plurality of tyre-like sections which are pressed together.

10. Apparatus according to any preceding claim, wherein the rotatable hollow body is provided with a thrust ring for engaging one or more thrust rollers connected to a base of the apparatus to prevent the body sliding when the body is placed on an inclined to prevent the body climbing uphill during rotation thereof.

11. A method for grading pieces of granite by size, comprising charging a rotatable hollow body with pieces of granite, the surface of the hollow body having one or more apertures of a predetermined size and rotating the hollow body by means of rotating means comprising at least one roller contacting the surface of the body and motor means for rotating the roller so that pieces of granite below a predetermined size pass through the aperture(s).

12. Apparatus suitable for grading pieces of granite by size substantially as hereinbefore described, with reference to, and as illustrated in, the accompanying drawings.