GB2110113A - Impeller bar for hammer type mill - Google Patents

Abstract

An impeller bar 1 for a hammer type mill incorporates a plurality of peripherally located, hard material inserts 7, preferably located in axially extending rows 6. Each insert is brazed in a blind hole. <IMAGE>

Description

SPECIFICATION Impeller bar for hammer type mill This invention relates to an impeller bar for a hammer type mill, for the pulverising of minerals, refuse etc., and to a hammer type mill provided with such an impeller bar.

Conventionally, impeller bars of hammer type mills have fixed or swingable hammers attached to a rotor, which is conventionally rotatable about a horizontal axis, the impeller bars cooperating with one or more fixed anviis to produce the desired pulverising effect. The service conditions inevitably produce substantial wear on the impeller bars, resulting in relatively frequent replacement and hence down time of the mill. Attempts to extend the service life of impeller bars have included such techniques as hard face welding, and the industry has hitherto accepted the relatively short service life even of bars incorporating hard face welding. In other industrial applications, such as mineral cutting tools, whether for mineral winning operations, or for road planing operations, hard material inserts e.g.

of tungsten carbide, have been fitted to the tools involved to provide a lengthened service life, and although such mineral cutting tools have been known for many years, they have not influenced the design of hammer mills nor the impeller bars thereof.

According to the present invention there is provided an impeller bar for a hammer type mill incorporating a plurality of peripherally located, hard material inserts.

The invention also includes a hammer type mill provided with an impeller bar as defined above.

Conveniently, the inserts are of tungsten carbide, but other hard metal carbides may be employed. It is preferred for the inserts to be located along the full axial length of the impeller bar and conveniently each insert is constructed from a plurality of insert pieces located together end-to-end. With this last mentioned construction it may be arranged for the inserts to extend continuously from endto-end of the impeller bar, or alternatively for gaps to be provided between adjacent ends of adjacent insert pieces. Alternatively, the inserts may taken the form of relatively small studs secured e.g. by brazing, in axially spaced apart apertures. In one preferred construction two peripherally spaced rows of inserts are provided on each impeller bar.

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawing, which is an isometric view of one end of an impeller bar in accordance with the invention.

An elongate impeller bar is indicated generally at 1 and a plurality of such bars are secured, in the known manner, axially along the periphery of a rotor (not shown) of a hammer type mill, with a rear face 2 of the impeller bar 1 being provided with a tongue and groove profile 3 for location purposes on the rotor. An outer periphery 4 of the impeller bar 1 is located, in service, remote from the rotor and is provided, along peripherally spaced chamfered edges 5, with a row 6 of axially spaced apart tungsten carbide inserts 7 of circular section, each insert 7 being brazed in a blind hole 8.The rows 6 are provided at locations on the impeller bar 1 where a major part of the pulverising action of the mill will be effected and hence where extensive wear would normally be expected, the extreme wear resistant properties of the inserts protecting the adjacent material of the impeller bar 1 ànd hence extending the service life thereof.

1. An impeller bar for a hammer type mill incorporating a plurality of peripherally located, hard material inserts.

2. An impeller bar as claimed in Claim 1, wherein the inserts are of tungsten carbide.

3. An impeller bar as claimed in Claim 1 or Claim 2, wherein the inserts are located along the full axial length of the impeller bar.

4. An impeller bar as claimed in any preceding Claim, wherein each insert is constructed from a plurality of insert pieces located together end-to-end.

5. An impeller bar as claimed in Claim 4, wherein the inserts extend continuously from end-to-end of the impeller bar.

6. An impeller bar as claimed in Claim 4, wherein gaps are provided between adjacent ends of adjacent insert pieces.

7. An impeller bar as claimed in any one of Claims 1 to 3, wherein the inserts take the form of relatively small studs.

8. An impeller bar as claimed in Claim 7, wherein the studs are secured in axially spaced apart apertures.

9. An impeller bar as claimed in Claim 8, wherein the studs are secured by brazing.

10. An impeller bar as claimed in any preceding Claim, wherein two peripherally spaced rows of inserts are provided on each impeller bar.

11. An impeller bar substantially as hereinbefore desribed with reference to the accompanying drawing.

1 2. A hammer type mill provided with an impeller bar as defined in any preceding Claim.

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

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Impeller bar for hammer type mill This invention relates to an impeller bar for a hammer type mill, for the pulverising of minerals, refuse etc., and to a hammer type mill provided with such an impeller bar. Conventionally, impeller bars of hammer type mills have fixed or swingable hammers attached to a rotor, which is conventionally rotatable about a horizontal axis, the impeller bars cooperating with one or more fixed anviis to produce the desired pulverising effect. The service conditions inevitably produce substantial wear on the impeller bars, resulting in relatively frequent replacement and hence down time of the mill. Attempts to extend the service life of impeller bars have included such techniques as hard face welding, and the industry has hitherto accepted the relatively short service life even of bars incorporating hard face welding. In other industrial applications, such as mineral cutting tools, whether for mineral winning operations, or for road planing operations, hard material inserts e.g. of tungsten carbide, have been fitted to the tools involved to provide a lengthened service life, and although such mineral cutting tools have been known for many years, they have not influenced the design of hammer mills nor the impeller bars thereof. According to the present invention there is provided an impeller bar for a hammer type mill incorporating a plurality of peripherally located, hard material inserts. The invention also includes a hammer type mill provided with an impeller bar as defined above. Conveniently, the inserts are of tungsten carbide, but other hard metal carbides may be employed. It is preferred for the inserts to be located along the full axial length of the impeller bar and conveniently each insert is constructed from a plurality of insert pieces located together end-to-end. With this last mentioned construction it may be arranged for the inserts to extend continuously from endto-end of the impeller bar, or alternatively for gaps to be provided between adjacent ends of adjacent insert pieces. Alternatively, the inserts may taken the form of relatively small studs secured e.g. by brazing, in axially spaced apart apertures. In one preferred construction two peripherally spaced rows of inserts are provided on each impeller bar. The invention will now be described in greater detail, by way of example, with reference to the accompanying drawing, which is an isometric view of one end of an impeller bar in accordance with the invention. An elongate impeller bar is indicated generally at 1 and a plurality of such bars are secured, in the known manner, axially along the periphery of a rotor (not shown) of a hammer type mill, with a rear face 2 of the impeller bar 1 being provided with a tongue and groove profile 3 for location purposes on the rotor. An outer periphery 4 of the impeller bar 1 is located, in service, remote from the rotor and is provided, along peripherally spaced chamfered edges 5, with a row 6 of axially spaced apart tungsten carbide inserts 7 of circular section, each insert 7 being brazed in a blind hole 8.The rows 6 are provided at locations on the impeller bar 1 where a major part of the pulverising action of the mill will be effected and hence where extensive wear would normally be expected, the extreme wear resistant properties of the inserts protecting the adjacent material of the impeller bar 1 ànd hence extending the service life thereof. CLAIMS

1. An impeller bar for a hammer type mill incorporating a plurality of peripherally located, hard material inserts.

2. An impeller bar as claimed in Claim 1, wherein the inserts are of tungsten carbide.

3. An impeller bar as claimed in Claim 1 or Claim 2, wherein the inserts are located along the full axial length of the impeller bar.

4. An impeller bar as claimed in any preceding Claim, wherein each insert is constructed from a plurality of insert pieces located together end-to-end.

5. An impeller bar as claimed in Claim 4, wherein the inserts extend continuously from end-to-end of the impeller bar.

6. An impeller bar as claimed in Claim 4, wherein gaps are provided between adjacent ends of adjacent insert pieces.

7. An impeller bar as claimed in any one of Claims 1 to 3, wherein the inserts take the form of relatively small studs.

8. An impeller bar as claimed in Claim 7, wherein the studs are secured in axially spaced apart apertures.

9. An impeller bar as claimed in Claim 8, wherein the studs are secured by brazing.

10. An impeller bar as claimed in any preceding Claim, wherein two peripherally spaced rows of inserts are provided on each impeller bar.

11. An impeller bar substantially as hereinbefore desribed with reference to the accompanying drawing.

1 2. A hammer type mill provided with an impeller bar as defined in any preceding Claim.