GB2128499A - Impact breakers - Google Patents

Abstract

An impact breaker rotor 1 comprises hammers formed by at least two impeller bars 2 each secured in a recess 3 extending longitudinally of the rotor 1, and barrier means 26 viz a bare or strap across each end of each recess. At least one of the barrier means of each recess is removable. <IMAGE>

Description

SPECIFICATION Impact breakers This invention relates to impact breakers for rock or mineral and of the type having hammers formed by two or more impeller bars secured in recesses along a rotor, usually by wedges and/or bolts, each impeller bar usually being formed with at least two longitudinal hammer faces on a section enabling the bar to be rotated about its longitudinal axis and/or reversed end-to-end to present an alternative face when one has worn.

Thus, it is known to have a "Z"-section or an "I"-section affording respectively two hammer faces or four hammer faces, but it is difficult to provide adequate support for the flange presenting a working hammer face and to prevent undue stressing of the diagonal of the "Z"-section or the web of the "l"-section by a fixing wedge engaged between the diagonal or web and one side of the recess in the rotor. Therefore, an alternative is known in which a generally rectangular-section impeller bar has a longitudinal groove in one broad side engaged by a rib on a wedge. In each case using wedges the recesses must be correspondingly narrower at the periphery of the rotor than at the bottoms of the recesses, to ensure that the wedges secure the impeller bars.

Again, an alternative is known in which a generally rectangular-section impeller bar has a longitudinal rib on one broad side engaged in a groove in a beam having a wedge portion engaged in a recess of corresponding section in the rotor, the impeller bar being bolted to the beam.

Service conditions necessarily result in substantial wear on the impeller bars, resulting in relatively frequent rotation and/or reversal and replacement, and hence appreciable down-time of the impact breaker, particularly in view of the time involved in freeing and resetting wedges or unscrewing and screwing bolts, as well as separating and re-assembling the parts.

One object of the invention is to provide an impact breaker rotor with hammers formed by two or more impeller bars secured in recesses along a rotor and which does not have the disadvantages referred to above.

Another object of the invention is to provide an impact breaker rotor of the same type which is of particularly simple construction.

According to the present invention, there is provided an impact breaker rotor comprising hammers formed by at least two impeller bars each secured in a recess extending longitudinally of the rotor, each impeller bar having a rear face (with respect to the direction of rotation of the rotor, in use) abutting an adjacent first face of its recess and having an opposite, front face provided with a longitudinal groove affording an easy fit round a rib extending along an adjacent, second face of its recess, the section of each impeller bar being symmetrical about a smaller longitudinal mid-plane and having an overall thickness between its front and rear faces affording an easy fit between first and second faces of its recess, and an overall width affording clearance in the bottom of its recess, the first face of each recess having a greater radial extent that the radial extent of the second face by less than the width of the portion of the front face of its impeller bar beyond one side of the groove therein, and barrier means across each end of each recess, at least one barrier means of each recess being removable.

Thus, with the barrier means at one end of each recess removed the impeller bars are readily inserted or removed endwise, but when in place in the recesses with the barrier means in place at both ends of each recess the easy fit of the respective ribs and grooves ensures absolute security of the impeller bars, while the mating of the ungrooved faces of the impeller bars with the respective rear faces of the recesses ensures adequate support behind the working hammer faces constituted by the respective portions of the grooved faces of the impeller bars projecting radially beyond the respective front faces of the recesses.The depth of the grooves in the impeller bars can be modest compared with the overall thickness of the impeller bars, so that the resistance to bending at the middle is high and in consequence -- impact forces on each working hammer face transmitted through the respective bar to the rotor will be distributed over substantially the full radial extent of the mating rear faces of the bar and the recess, even though the bar is an easy fit in the recess.

Conveniently, each barrier means consists of a bar or strap secured across its recess by a bolt at each end, which bolts need to be removed to allow the bar to be swung clear of the recess.

According to a further and preferred feature of the invention, each recess is formed by a parallelsided slot in the rotor body, while the first and second faces of the slot are provided respectively on a pair of face plates secured in spaced apart relationship, the face plate secured to the front side of the slot being provided with the longitudinal rib. Conveniently, the face plates are secured to the rotor by welding, while each pair of face plates may be separated from one another by a spacer plate located at the bottom of the slot, the spacer plate may be secured by threaded studs to the bottom of the slot, and the face plates may be secured to their spacer plate by welding.

Preferably, each parallel side of each slot is interrupted by a longitudinally extending groove, to receive a correspondingly profiled rib on each face plate, whereby the face plates are keyed into the rotor, in addition to being welded to the rotor.

Each face plate is preferably provided at each end with a tapped hole for a bolt or barrier means.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a small scale end elevation of an impact breaker rotor in accordance with the invention; and Figure 2 is an enlarged fragmentary crosssection of one recess and its impeller bar.

The impact breaker rotor 1 shown in the drawings has hammers formed by two impeller bars 2 secured in recesses 3 extending longitudinally of the rotor 1. Each recess 3 is formed by a parallel-sided slot 4 having a rear face 5 and a front face 6, having regard to the direction of rotation of the rotor, the faces 5 and 6 being interrupted respectively by longitudinal grooves 7 and 8. To the rear face 5 is applied a rear face plate 9 having a longitudinally extending rib 10 of dimensions approximating to that of the groove 7, whereby the rear face plate 9 is keyed to the rotor 1, and furthermore the rear face plate 9 is secured by weld metal 11 to the rotor 1.Similarly, to the front face 6 is applied a front face plate 12 having a longitudinally extending rib 1 3 of dimensions approximating to that of the groove 8, so that the front face plate 12 is keyed to the rotor 1 and furthermore the front face plate 12 is secured by weld metal 14 to the rotor 1. The face plates 9 and 12 extend to the bottom of the slot 4, which bottom is defined by a face 15, into which are drilled a plurality of tapped holes (not shown) to receive securing studs 1 6 for a spacer plate 1 7 extending between the face plates 9 and 12 and welded to each at 1 8 and 1 9 respectively.The rear face plate 9 has a planar front face 1 9 to which is butted a planar rear face 20 of the impeller bar 2, while a front face 21 of the impeller bar 2 is provided with a longitudinal groove 22, which makes an easy, mating fit with a longitudinal rib 23 projecting from a rear face 24 of the front face plate 12. Each face plate 9, 12 is provided at each end with a tapped hole to receive a bolt 25 of a barrier means 26 in the form of a bar or strap, the bolts 25 being removable to remove the strap 26 to enable replacement of the impeller bar 2 to be effected, for replacement or reversal purposes.

The section of each impeller bar 2 is symmetrical about its smaller longitudinal midplane 27, each bar having an overall thickness T affording an easy fit between the front face 1 9 of the rear face plate 9 and the rear face 24 of the front face plate 12, and an overall width W affording clearance C between the spacer plate 1 7 and the adjacent edge of the bar 2. Furthermore, the front face 1 9 of the rear face plate 9 has a greater radial extent than has the rear face 24 of the front face plate 12, the radial extent of the rear face 24 terminating within a distance D over which extends a working face 28 of the front face 21 of the impeller bar beyond the groove 22.

The easy fit of the respective ribs 23 and grooves 22 ensures absolute security of the impeller bars 2, while the abutment of the planar faces 1 9 and 20 of the rear face plate 9 and impeller bar 2 respectively, ensures adequate support behind the working hammer faces 28. The depth d of the grooves 22 in each impeller bar 2 is modest compared with their overall thickness T, so that the resistance to bending about the middle is high and - in consequence -- impact forces on each working hammer face 28 transmitted through the respective bar 2 to the rotor will be distributed over substantially the full radial extent of the abutting faces 20 and 1 9, even though the bar is an easy fit in the recess.

Claims (13)

1. An impact breaker rotor comprising hammers formed by at least two impeller bars each secured in a recess extending longitudinally of the rotor, each impeller bar having a rear face (with respect to the direction of rotation of the rotor, in use) abutting an adjacent first face of its recess and having an opposite, front face provided with a longitudinal groove affording an easy fit round a rib extending along an adjacent, second face of its recess, the section of each impeller bar being symmetrical about a smaller longitudinal mid-plane and having an overall thickness between its front and rear faces affording an easy fit between first and second faces of its recess, and an overall width affording clearance in the bottom of its recess, the first face of each recess having a greater radial extent than the radial extent of the second face by less than the width of the portion of the front face of its impeller bar beyond one side of the groove therein, and barrier means across each end of each recess, at least one barrier means of each recess being removable.

2. A rotor as claimed in Claim 1, wherein the depth of the grooves in the impeller bars is small compared with the overall thickness of the impeller bars.

3. A rotor as claimed in Claim 1 or Claim 2, wherein each barrier means consists of a bar or strap secured across its recess by a bolt at each end.

4. A rotor as claimed in any preceding Claim, wherein each recess is formed by a parallel-sided slot in the rotor body.

5. A rotor as claimed in Claim 4, wherein the first and second faces of the slot are provided respectively on a pair of face plates secured in spaced apart relationship within the slot, the face plate secured to the front side of the slot being provided with the longitudinal rib.

6. A rotor as claimed in Claim 5, wherein the pair of face plates are secured to the rotor by welding.

7. A rotor as claimed in Claim 5 or Claim 6, wherein the pair of face plates are separated by a spacer plate located at the bottom of the slot.

8. A rotor as claimed in Claim 7, wherein the spacer plate is secured by threaded studs to the bottom of the slot.

9. A rotor as claimed in Claim 8, wherein the face plates are secured to their spacer plate by welding.

10. A rotor as claimed in Claim 5 or Claim 6, wherein each parallel side of each slot is interrupted by a longitudinally extending groove, to receive a correspondingly profiled rib on each face plate, whereby the face plates are keyed into the rotor, in addition to being welded to the rotor.

11. A rotor as claimed in Claim 5, wherein each face plate is provided at each end with a tapped hole for a bolt of its barrier means.

12. An impact breaker rotor substantially as hereinbefore described with reference to the accompanying drawing.

13. An impact breaker provided with a rotor as defined in any preceding Claim.