GB2320447A

GB2320447A - Improvements in hammer mills

Info

Publication number: GB2320447A
Application number: GB9725210A
Authority: GB
Inventors: Christopher Francis Jam Graham
Original assignee: SEVALE ENGINEERING Ltd
Current assignee: SEVALE ENGINEERING Ltd
Priority date: 1996-12-18
Filing date: 1997-12-01
Publication date: 1998-06-24
Also published as: GB9626226D0; GB9725210D0

Abstract

In a hammer mill the beater plates (18) are of reduced length and fixed to and in alignment with holders (19) pivotally attached to a disc (11). The reduced-length plates are reversible in position to provide a second working end when one end is worn and the plates (18) are readily replaceable on the holders (19) thus reducing material wastage and machine down time. The holders (19) may be of less durable material than the plates (18) and are preferably mounted on enlarged bushes (24) to avoid wear at the pivotal connection to the disc (11).

Description

IMPROVEMENTS IN HAMMER MIllS THIS INVENTION concerns a hammer mill of the kind including a rotor consisting of several disc-like members mounted at axially spaced positions along a rotated shaft and located within a perforated drum or screen into which friable material to be granulated, is supplied. On each disc is mounted a set of beaters consisting usually of four elongated plates pivotally mounted in the peripheral region of the disc such that when the shaft is rotated the beaters centrifugally extend radially from the rotor and are driven thereby to force material to be milled through the perforations in the drum.

Conventionally, such beaters wear rapidly in use and must be replaced at frequent intervals.

For economy, it is known for each beater to be made with a pair of location apertures, one adjacent each end whereby when one end of the beater becomes worn it can be turned around and/or mounted on its other end whereby, in effect, four separate corners are usable before the beater must be scrapped. Replacement of the beaters is expensive in raw material and in machine down time.

According to the present invention there is provided a beater for a hammer mill having a rotor driven in rotation within a perforated drum, the beater comprising an elongate plate with means for pivotal attachment thereof to the rotor to extend radially therefrom within the drum; characterised in that the plate is of reduced length to occupy, in a hammer mill, only a part of the radial space between the rotor and the drum.

Preferably, said means is a holder pivotally attachable to the rotor, the plate being removably attached to the radial free end of the holder and having means for selectively attaching one or other end thereof to the holder thus to be in rigid alignment therewith.

Still further, the holder preferably carries an enlarged bush or pin for pivotally mounting it upon the rotor thus to avoid wear in the pivotal attachment of the beater to the rotor.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 illustrates, in transverse cross-section, a hammer mill including conventional beaters.

Fig. 2 illustrates a beater made in accordance with the invention; and Fig. 3 is a side view of the beater illustrated in Fig. 2.

As shown in Fig. 1, in a hammer mill, a central rotary shaft 10 has mounted thereon a series of axially spaced discs 11 each carrying at its periphery a plurality of beaters 12 freely pivotally attached at 13 to the disc. As can be seen, the free end 14 of each beater extends to within close proximity with the internal surface of a stationary perforated drum 15 such that material 16 contained within the drum is forced outwardly through the perforations to produce a uniform granulation of the material.

Because of the nature of the material and the physical work imposed thereon by the beaters 12 the leading corners of the free ends thereof rapidly become worn requiring frequent replacement of the beaters 12. Between replacements, the beaters may be turned around so that the previously trailing corners are leading.

In order further to increase the life of the beaters, they may be provided with a second aperture 17 such that they are reversibly attachable to the discs 11. However, once both corners at both ends of the beaters are worn they must be replaced and this involves considerable machine down time and usually requires that a full set of beaters be replaced at one time thus to ensure balance and optimum working of the machine.

Thus the beaters, although of hardened or even mild steel, are an expensive consumable in the operation of a hammer mill and so in accordance with the present invention with reference to Figs. 2 and 3 of the drawings the beaters 12 which conventionally may be some 16 cm in length are replaced by shorter plates 18 (approximately 8 cm) mounted on an enlarged disc 11 or on a holder 19, itself pivotally mounted on the disc.

When used with a holder 19 each beater plate 18 is attached thereto by a pin 20 and spring clip 21. An aperture 22 in the plate 18 receives a locating pin 23 fixed to the holder 19, to maintain the plate in rigid alignment with the holder. Again, a further aperture 22' may be provided such that the plate 18 is reversibly attachable to the holder 19 thus to extend the working life of the beater plate.

As can be seen the holder 19 which may be of less durable material than the beater plate 18 preferably contains a fixed bush 24 of enlarged diameter when compared with a conventional pivotal attachment pin. When incorporated within a hammer mill with "open" type rotors provision of the enlarged pivotal bush 24 considerably reduces wear in the pivotal connection to the disc so that the holder becomes a permanent, or at least less-frequently replaceable, item within the machine.

In some hammer mills the shortened plate 18 may be attached directly to an enlarged diameter disc or a disc having radial extensions thereon, but preferably, and where maximum space is required between the circumference of the disc and the drum 15, the holders 19 are incorporated.

The spring clip 21 permits rapid reversal or removal of the beater plates thus minimising machine down time for replacement.

If preferred, the plates may be bolted to the holders.

It is envisaged that hammer mill beaters made in accordance with the invention will considerably reduce the manufacturing and operating costs of a hammer mill when compared with conventional, full length, beaters. Also the beaters and holders may be made from a cheaper cast material, having if required an integrally cast distance piece at the position of attachment to the rotary disc.

Claims

1. A beater for a hammer mill having a rotor driven in rotation within a perforated drum, the beater comprising an elongate plate with means for pivotal attachment thereof to the rotor to extend radially therefrom within the drum; characterised in that the plate is of reduced length to occupy, in a hammer mill, only a part of the radial space between the rotor and the drum.

2. A beater for a hammer mill according to Claim 1, the beater being of reduced length and mounted on an enlarged disc.

3. A beater for a hammer mill according to Claim 1, wherein the means for its pivotal attachment to the rotor comprises a holder pivotally attachable to the rotor, the plate being removably attached to the radial free end of the holder and having means for selectively attaching one or other end of the plate to the holder thus to be in rigid alignment therewith.

4. A beater for a hammer mill according to Claim 3, wherein the holder carries an enlarged bush or pin for pivotally mounting it upon the rotor thus to avoid wear in the pivotal attachment of the beater to the rotor.

5. A beater for a hammer mill according to Claim 3 or Claim 4, wherein the plate is bolted to the beater.

6. A beater for a hammer mill according to Claim 3 or Claim 4, wherein the plate is attached to the holder by a pin and spring clip, an aperture in the plate receiving a locating pin fixed to the holder to maintain the plate in rigid alignment therewith.

7. A beater for a hammer mill according to any one of Claims 3 to 6, wherein the holder is of less durable material than the beater plate.

8. A beater for a hammer mill according to Claim 1 or Claim 2, wherein a reduced length plate is attached directly to a disc having radial extensions thereon.

9. A beater for a hammer mill, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings;