US3637147A

US3637147A - Lifting members in wear lining for rotary drums

Info

Publication number: US3637147A
Application number: US865390A
Authority: US
Inventors: Robert Gerhard Franz Jo Naredi
Original assignee: Cementa AB; Skega AB
Current assignee: Cementa AB; Skega AB
Priority date: 1968-10-11
Filing date: 1969-10-10
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25
Also published as: FI52284B; DE1951235C3; DE1951235A1; FI52284C; GB1288083A; NO131573C; DE1951235B2; NO131573B; FR2020440A1

Abstract

This invention relates to lifting members for the wear lining of rotary drums employed in particle comminuting and sorting apparatus, such as mills, the members being placed in spaced relationship alongside of each other. Separate wear protecting elements are supported between each pair of lifting members, and the lifting members and the associated wear protecting elements are mounted along generatrices of the drum, i.e., the center line of each lifting member coincides with a drum generatrix.

Description

Jan. 2, 1972 aredi 3333 8888 31111 I/ Ill] /4444 2222 4 u u u" 2 u u ":Lv n t ahuflhm mw ec rS ba 8000K CPRFT 52799 25556 99999 lllll 69039 Primary Examiner-Donald G. Kelly Attorney-Summers & Young Sltega AB, Ersmark, Czechoslovakia [22] Filed: 0ct.10,l969

[21] Appl.No.:

[57] ABSTRACT This invention relates to lifting members for the wear lining of [30] Foreign Application Priority Dam rotary drums employed in particle comminuting and sorting apparatus, such as mills, the members being placed in spaced relationship alongside of each other. Separate wear protecting Oct. 1l,l968 Sweden................................l3730/68 elements are supported between each pair of lifting members,

and the lifting members and the associated wear protecting elements are mounted along generatrices of the drum, i.e., the center line of each lifting member coincides with a drum generatrix.

3 (Claims, 5 Drawing Figures References Cited 1,309.2l0 Marcy............... ....24l/l83 X LIFTING MEMBERS IN WEAR lLllNING F'Ollt ROTARY DRUMS BACKGROUND OF THE INVENTION In rotary drums, it is in many cases necessary, owing to wear stresses, to line the drum shell with a wear-resistant lining. This is particularly the case in mills, such as ball mills or tube mills. The linings usually comprise plain or sectional plates secured by screwing onto the shell and end walls. Alternatively, shell and end wall plates may be bolted together with lifting members (so-called lifters) radially on end walls and along the generatrix on the shell. The lining may also be constructed or bar-shaped units placed side by side and held at the ends by clamping rings secured on the shell by screws. Said bar-shaped units may be placed so as to deviate from the generatrix and thereby form a so-called helical lining. This brings about a sizing effect on the charge, in such a way that grinding elements of greater dimension accumulate at the inlet end wall where the material to be ground is fed into the mill, and the worn grinding elements are collected at the outlet end wall where the milling produce is finely ground. The sizing effect hereby results in an increase of grinding capacity.

A sizing effect is also obtained by the use of sectional plates according to U.S. Pat. No. 2,809,789. However, when the lifters on these plates become worn, the sizing effect rapidly ceases and the plates in their entirety must be exchanged. Such an exchange is uneconomic, because thereby a great portion of the lining is turned into scrap.

A corresponding sizing effect can be obtained by shell plates and separate lifters, if the latter are screwed into rows of holes deviating from the shell generatrices. The holes, thus, are to be drilled along helical lines deviating from said generatrices. In existing mills, with hole rows drilled in a conventional way along generatrices, it can be impossible in many cases, for strength reasons, to drill new rows of holes along helical lines. It further involves the drawback that every wear lining of steel, depending on different deviations from the generatrix and on varying mill diameters, must then be specially manufactured in forms rendering the correct helical shape for obtaining good abutment to the shell. When using rubber, however, the plates and lifting members can be designed for being clamped along generatrices and yet be clamped to form a helix, because the members are elastomeric and deform when being mounted.

SUMMARY OF THE INVENTION The present invention has as its object to overcome the disadvantage that hole rows are to be drilled in the shell along helical lines, in order to avoid any reduction in the strength of the shell. By the present invention, existing hole rows are utilized even if one desires to vary the helix angle. Other advantages of the invention will gradually become evident from the following description.

The lifting members according to the invention substantially are characterized in that the lifting portion of the lifting member, i.e., that portion which meets the material being ground and which comprises at least one side surface, so deviates from the generatrix that every surface of the lifting portion, at that end of the side surface which is located closest to the outlet end is nearer the centerline of the lifting member than at the inlet end of the drum.

According to the invention, the wear protection may comprise on single plate, or several plates arranged one after the other, or several bar-shaped units placed side by side, or suitable combinations thereof, and it may be made of any suitable material, for example rubber or steel. The mounting of the wear lining can be carried out in any suitable way, for example such as described in U.S. Pat. No. 3,107,867. The lifting members preferably are manufactured separately.

According to the invention, it is suitable that those surfaces of the lifting members which face to the center of the drum preferably taper towards the outlet end of the drum with an angle deviating from the generatrix by up to It was found that when the lifting members are laid in along the generatrices on the shell and designed in a conventional way, in many cases the segregation (sizing) will be inverse, in such a way, that the heavy grinding elements collect at the outlet end and the (worn) grinding elements of a lighter weight have the tendency of collecting at the inlet end. For counteracting this inverse segregation, a deviation of one side surface of the lifting members by about O.5 is in many cases sufficient. For achieving a distinct sizing effect, with drums having a diameter of up to 2.5 meters the deviation of one side surface of the lifting members preferably should be l.5-2.0 At greater drum diameters and with grinding elements of very great dimensions, the effect will be improved by slight increase of the angle. If sizing is desired to be effected on a very short distance, advantageously an angle deviation of l0-l5 is used. The aforesaid deviations were fbund to apply to numbers of revolutions usually applied (65-80 percent of the critical number of revolutions).

BRIEF DESCRIPTION OF THE DRAWINGS Some embodiments of the invention are described in the following, with reference to the accompanying drawing in which:

FIG. I shows a view seen from above of a lifting member according to the invention,

FIG. 2 shows the same lifting member in a section along the line Il-II in FIG. ll,

FIG. 3 shows a view seen from above of a second embodiment of the invention, the invention,

FIG. 4 shows a view seen from above of a third embodiment of the invention, and

FIG. 5 shows an application of the invention in a grate discharge mill.

FIGS. I and 2 show a lifting member 1 which, seen from above, has a rectangular longitudinal shape. The lifting member is mounted along the shell generatn'x by means of suitable fastening means (not shown) possibly through each of the three holes 2 located along the lifting member centerline 6 coinciding with a generatrix. The lifting member holds the wear protecting elements 3 in such a manner, that the lifting member is embedded in recesses in edge portions of the wear protecting elements. Of the two

longitudinal side surfaces

4 and 5 of the lifting member projecting upwardly above the wear protection, the side surface 4 is the lifting side surface, and this side surface deviates from the generatrix of shell 7. The portion located above the wear protection, thus, tapers towards the outlet end of the drum. The angle deviation in this case is about 2. As an alternative, the lifter can be given a rounded top surface.

FIG. 3 shows a view of a second embodiment of a lifting member according to the invention. It differs from the embodiment in FIGS. I. and 2 only in that both side surfaces 8 and 9 of the lifting member which are located above the wear protection deviate from the shell generatrix. The centerline 6 of the lifting member coincides with a generatrix.

FIG. 4 shows a third embodiment of the invention according to which the lifting side 10 of the lifting member deviates from the generatrix by an, angular tooth shape which allows for a greater number of deviation degrees from the generatrix.

FIG. 5 shows how the lifting members I according to the invention can be built into a grate discharge mill II with inlet 12 and outlet 13. The drum is provided with lifting members I and wear protecting elements 3 along the greater part of the inner shell surface. Immediately adjacent the outlet 13 a grate I5 is mounted, the perforations of which determine the maximum grain size of the ground product. The mill is charged with the material to be ground and with grinding elements.

In many cases such the grinding elements, or at least part of them, are worn to such a size that they clog the grate, which causes troubles in the form of capacity decline or operation interruptions or, at worst, operation breakdown. If, thus, the mill is equipped only with lifting members of the type designated by 1, such inconveniences can occur. By inserting immediately before the grate one or several sections of lifting members of the type which in FIG. 5 is designated by 16, the aforesaid inconvenience can be eliminated.

Every section may comprise either only lifting members according to the'invention, or a combination of lifting members according to the invention and of conventional lifting members. The lifting side of the lifting member 16 with the lifting side surface 17 faces to the opposite direction, so that the (worn) grinding elements of smaller dimensions which have caused the clogging of the grate are lifted back, and only the grinding elements of somewhat greater dimensions which are too large for clogging the grate are allowed to be active at the grate. The critical" grinding elements of smaller dimensions are thereby subjected to an additional wear or preferably are worn completely so as to have the same grain size as the pulp in general. These elements are then combined with the pulp and pass together with the pulp through the grate. The result is a considerably reduced clogging of the grate. If the grinding elements are of a grain size exceeding that of the pulp grains, this will increase the wear in pumps, pipes and classifiers.

This utilization of the invention has been described in connection with a grate discharge mill, but the same principle, of course, can be applied to other mills equipped with grate, for example partition walls in sludge mills for control of the maximum grain size of grinding elements and/or the ground product. That side surface of the lifting member 16 which lifts back can be designed with a deviation from the shell generatrix corresponding to the demand in question. The effect of said "lifting back increases with increasing deviation. Experiments made with l0l5 have succeeded well.

What I claim is:

1. In a rotary drum ofa comminuting mill or the like the improvement which comprises a plurality of elongate lifting members secured in generally side-by-side relationship along the interior surface of the drum, each said lifting member lying with its longitudinal axis along a generatrix of the cylindrical interior surface of the drum,

each said lifting element having one side surface which acts as the lifting surface during drum rotation and which is, over at least a portion of its length, disposed to form an acute angle to said longitudinal axis and thus also to the respective generatrix along which the respective lifting element lies whereby said one side surface lies toward the drum outlet end closer to said longitudinal axis than at the inlet end ofthe drum.

2. The apparatus of claim 1 which further includes at least on wear protecting element between each pair of lifting elements.

3. The apparatus of claim 1 in which the surface of each said lifting element which faces the center of said drum is tapered toward the outlet end of the drum at an angle to the associated generatrix of as much as 15.

Claims

1. In a rotary drum of a comminuting mill or the like the improvement which comprises: a plurality of elongate lifting members secured in generally side-by-side relationship along the interior surface of the drum, each said lifting member lying with its longitudinal axis along a generatrix of the cylindrical interior surface of the drum, each said lifting element having one side surface which acts as the lifting surface during drum rotation and which is, over at least a portion of its length, disposed to form an acute angle to said longitudinal axis and thus also to the respective generatrix along which the respective lifting element lies whereby said one side surface lies toward the drum outlet end closer to said longitudinal axis than at the inlet end of the drum.

2. The apparatUs of claim 1 which further includes at least one wear protecting element between each pair of lifting elements.

3. The apparatus of claim 1 in which the surface of each said lifting element which faces the center of said drum is tapered toward the outlet end of the drum at an angle to the associated generatrix of as much as 15*.