CA1187060A - Mill construction - Google Patents
Mill constructionInfo
- Publication number
- CA1187060A CA1187060A CA000407482A CA407482A CA1187060A CA 1187060 A CA1187060 A CA 1187060A CA 000407482 A CA000407482 A CA 000407482A CA 407482 A CA407482 A CA 407482A CA 1187060 A CA1187060 A CA 1187060A
- Authority
- CA
- Canada
- Prior art keywords
- drum
- heads
- ring portions
- head
- adjacent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000010276 construction Methods 0.000 title abstract description 4
- 230000003014 reinforcing effect Effects 0.000 claims abstract description 9
- 238000003466 welding Methods 0.000 claims description 3
- 230000032798 delamination Effects 0.000 description 4
- 238000005452 bending Methods 0.000 description 2
- 102000004726 Connectin Human genes 0.000 description 1
- 108010002947 Connectin Proteins 0.000 description 1
- 244000187656 Eucalyptus cornuta Species 0.000 description 1
- 230000004323 axial length Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
- B02C17/04—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls with unperforated container
Landscapes
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Crushing And Grinding (AREA)
Abstract
MILL CONSTRUCTION
ABSTRACT OF THE DISCLOSURE
An improved mill structure is provided by means of a substantially cylindrical drum rotatable about its longitudinal axis on a pair of axially spaced trunnions. The drum is made of a cylindrical shell portion with a pair of cylindrical reinforcing ring portions concentric therewith and extending axially one from each end of the shell portion. The ring portions axe of greater thickness than the shell portion. The ends of the drum are connected by heads to the trunnions and the axial end of each of the ring portions remote from the shell portion are in a butting relationship with the inner face of the adjacent one of said heads and are connected thereto by connecting means spaced circumferentially about the head and extending through the head and secured to the adjacent of the ring portions thereby to connect the ring portions to their adjacent head. Each of said ring portions extend from the adjacent head by a distance such that the peak stress applied to the area of the junctions between the heads and the cylindrical body portions are accomodated within the thick ring portions.
ABSTRACT OF THE DISCLOSURE
An improved mill structure is provided by means of a substantially cylindrical drum rotatable about its longitudinal axis on a pair of axially spaced trunnions. The drum is made of a cylindrical shell portion with a pair of cylindrical reinforcing ring portions concentric therewith and extending axially one from each end of the shell portion. The ring portions axe of greater thickness than the shell portion. The ends of the drum are connected by heads to the trunnions and the axial end of each of the ring portions remote from the shell portion are in a butting relationship with the inner face of the adjacent one of said heads and are connected thereto by connecting means spaced circumferentially about the head and extending through the head and secured to the adjacent of the ring portions thereby to connect the ring portions to their adjacent head. Each of said ring portions extend from the adjacent head by a distance such that the peak stress applied to the area of the junctions between the heads and the cylindrical body portions are accomodated within the thick ring portions.
Description
~87~
FIELD OF TH~ INVE~TIO~
The present invention relates to a rotating drum structure, more particularly the present invention relates to a more economical rotatable drum structure that will accommodate the relatively heavy loads encountered in grinding millq or kilns.
BACKGROUND OF TH~ I~VE~TION
It is well known to construct grinding mills carrying gross mill loads in the order of 500,000 lbs.
whi.ch generate signiicantly high stresses in the mill structure, particularly at the junc~ion between the cylindrical drum portion or shell of the apparatus and the heads at opposite ends thereof. This is particularly true of mill strwctures wherein the mill is supported on trunnions projecting outward from the heads at opposite ends of the drum. The weight of the mill structure itself, the weight of the material being treated and the rolling action of this material within the mill as the mill rotates cause extremely high stress concentrations that tend to deflect and distort the shape o the mill.
It is conventional practice with such mills to secure the drum to the heads by substantially radially extending flanges secured ~by welding) to the .~.
3&~
FIELD OF TH~ INVE~TIO~
The present invention relates to a rotating drum structure, more particularly the present invention relates to a more economical rotatable drum structure that will accommodate the relatively heavy loads encountered in grinding millq or kilns.
BACKGROUND OF TH~ I~VE~TION
It is well known to construct grinding mills carrying gross mill loads in the order of 500,000 lbs.
whi.ch generate signiicantly high stresses in the mill structure, particularly at the junc~ion between the cylindrical drum portion or shell of the apparatus and the heads at opposite ends thereof. This is particularly true of mill strwctures wherein the mill is supported on trunnions projecting outward from the heads at opposite ends of the drum. The weight of the mill structure itself, the weight of the material being treated and the rolling action of this material within the mill as the mill rotates cause extremely high stress concentrations that tend to deflect and distort the shape o the mill.
It is conventional practice with such mills to secure the drum to the heads by substantially radially extending flanges secured ~by welding) to the .~.
3&~
-2-shell and bolts passing throu~h the head and adjacent radial flange. Such an arrangement is shown for example in U.S. Patent Number 3,401,~93 issued September 17, 1968 to Reynolds or or example in very early U. Sr Patent Number 634,254 issued October 3, 1899 to Yates. A similar type of cons~ruction is also shown in U.S. Pa~ent Number 3,272,444 issued September 13, 1966 to Richard et al.
U.S. Patent Number 3,448,067 issued January 26, 1971 to Jeness teaches a technique for reinforcing the ~hell by providing a thickened annular right angular member betweeen the cylindrical body portion or shell of the mill and the heads and to which the heads are holted. This member is formed by a cylindrical portion connected to the shell and a radial bolting flange and is made from material thicker than the drum or shell so that it can withstand higher stresses. The cylindrical portion and radial flange are welded together from two pieces of relatively thick plate by circumferentially extendiny welded joints that extend substantially parallel to the plane of the plate material from which the radial bolting flange is made. ~he bending action and axial ~txess to which this angular member is ~ubjected tend to enhance the possibility of delamination of the plate material forming this 1ange. Similar delamination problems wil normally be encountered with other welded flanged constructions wherein the weld extends substantially parallel to the plane o~ the plate from which the bolting flange is made, i.e., in conventional drum structure with radial bolting flanges welded to their ends.
It will be noted that forces are transferred between the drum or shell portion and the head through the angular joint one arm of which is formed by the 76~
flange to which the head is bolted. This angular connection applies a bending moment through the angular member and further modifies the forces transmitted between -the head and the drum or shell.
IJnited States Patent Number 1~087,967 issued February 24, 1914 to ~loussette discloses a mill structure supported by rollers bearing an annular ring member each forming an integral part of ~he drum shell and providing a thickened portion with tapped holes into which bolts for holding t~e frustro conical inl~t and outlet sections to the drum are threaded.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
It is the objective of the present invention to provide a simplified mill structure that reduces the cost of the mill and overcomes many of the difficulties in the prior art joint construction.
Broadly, the present invention cornprises a substantially cylindrical drum rotatable about its longitudinal central axis on a pair o axially spaced trunnions, said drum comprising a cylindrical body portion of a first radial thickness, a pair of cylindrical ring portions concentric with said body portion and extending axially one from each axial end o~ the body portion, said ring portions have a radial thickness greater than the said first radial thickness, heads at opposite ends of said dru~, the axial end of each o~ said ring portions remote from said body portion being in a butting relationship wit~
said inner face of the adjacent one of said heads, connectin~ means space circumferentially about and extending through each of said heads and secured to the adjacent one of said ring portions to connect said ring portions to their respective adjacent heads, said trunnions being connected to and extending axially outward of said heads, each of said rims extending .
74~6~
~OK 103-089-A
from its adjacent head by a distance to accommodate peak stresses applied to said drum when said drum is loaded and rotated on said trunnions.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features, objects and advantages will be evident from the following detailed description of the preferrad embodiments of the present invention taken in conjunction with the accompanying drawings in which :
Figure 1 shows an axial section view of the top half of the mill incorporating the prPsent invention 7 Figure 2 illustrates a typical peak stress condition in the cylindrical drum section adjacent the head.
DESCRIPTION OF THE PREFER~ED EMBODIMENTS
As shown in Figure 1, the mill 10 comprises a substantially cylindrical drum section 12 composed of a drum or shell central portion 14 and a pair of end reinforcing rings 16. Only one shell portion has been shown but the section 12 may be composed of a plurality of axially aligned cylindrical portion~ 14 interco~nected at adjacent ends. Regardle~s of the number of central portions the rings 16 will only be provided adjacent each of the heads 18. Connected to each o~ these rings 16 i8 a head 18 which is provided with an axially extending trunnion 20 for rotatably mounting the drum or mill 10. The mill may be driven by any suitable drive means, in the illustrated arrangement a suitable r:lng gear generally indicated at 22 has been shown for this purpose.
The cylindrical drum at 12 as indicated is formed by at least one cylindrical shell portion 14 the ends of which each have welded thereto be suitable welds 24 a reinforcing ring 16. The distance between these welds 24, i.e. the axial length of the reinforcing elements of rings 16 as indicated by a letter x and must be a minimum length sufficient to contain the peak stresses that are generated in the drum structure 12 as the mill, supported by the trunnions 20 is rotated under load. Obviously these welds 24 will be suitably located so as not to interfere with bolting of the liners (not shown) to the shell. It will be apparent that by selecting a ring of sufficient axial extent, this may be achieved.
The typical stress curve showing stresses vs distance from the head is shown in Figure 20 It can be seen that adjacent to head maximum stresses are encountered whereas spaced from the head depending on the si~e of the mill, etc. a significantly reduced stress concentration is observed. This permits the use of thinner plate to fabricate those portions of the drum 12 operating under lower stress conditions.
5enerally the minimum distancP x will be at least 8 inches and preferably greater than about 12 inches, however x may be determined specifically for any given installation.
It is important that the reinforcing ring 16 be connected directly to the adjacent head 18, via a connection means extending substantially axially of the cylindrical drum 12, i.e. the xight angular connection and the complicated stress loading have been replaced by a substantially straight line connection extending axially of the drum.
Tn the illustrated arrangement the connection between the drum and head is obtained by a plurality of bolts 26 projecting through the head and threaded into the reinforcing rings 16~ Obviously the thickness of these rings must be ample to accommodate the size of bolts 26 used in securing the heads to the ~3'7~
drum section 12 but more important this increased thickness will be suficient to reduce the stress concentration ~o acceptable levels for the material used~
It will be noted that the welds 24 between the cylindrical body portion 12 and the rims 16 are spaced significantly (minimum distance xj from the end edges of the drum section 12, i.e. from the heads 18, Thi9 structure permits the use of automatic welding equipment to form these welds and thereby ensure that a relative uniform weld is obtained (as compared with manually welded joint) that was required with the right angle connection~
It will be further noted that the reinforcing area formed from plate material by appropriately curving the rol].ed faces of the plate material into cylindrical form and ~he ring i9 aligned with the cylindrical body section 12 and with the bolts or studs 26 so that the rolled surfaces of the plate material (delamination planes) with the direction of force transmis~ion between the heads 18 and the cylindrical drum 12 and the risk of delamination of the plate material is substantially eliminated.
By fabricating mill structure 10 as above described it has been ~ound that the inner drum or shell portion or portions 14 may be signifantly thinner than the thickness in the zone of the rein~orcing ring 16 whereby the cost of the mill may be significantly reduced, Modifications will be evident to those in the art without departing from the spirit of the invention as defined in ~he appended claims.
U.S. Patent Number 3,448,067 issued January 26, 1971 to Jeness teaches a technique for reinforcing the ~hell by providing a thickened annular right angular member betweeen the cylindrical body portion or shell of the mill and the heads and to which the heads are holted. This member is formed by a cylindrical portion connected to the shell and a radial bolting flange and is made from material thicker than the drum or shell so that it can withstand higher stresses. The cylindrical portion and radial flange are welded together from two pieces of relatively thick plate by circumferentially extendiny welded joints that extend substantially parallel to the plane of the plate material from which the radial bolting flange is made. ~he bending action and axial ~txess to which this angular member is ~ubjected tend to enhance the possibility of delamination of the plate material forming this 1ange. Similar delamination problems wil normally be encountered with other welded flanged constructions wherein the weld extends substantially parallel to the plane o~ the plate from which the bolting flange is made, i.e., in conventional drum structure with radial bolting flanges welded to their ends.
It will be noted that forces are transferred between the drum or shell portion and the head through the angular joint one arm of which is formed by the 76~
flange to which the head is bolted. This angular connection applies a bending moment through the angular member and further modifies the forces transmitted between -the head and the drum or shell.
IJnited States Patent Number 1~087,967 issued February 24, 1914 to ~loussette discloses a mill structure supported by rollers bearing an annular ring member each forming an integral part of ~he drum shell and providing a thickened portion with tapped holes into which bolts for holding t~e frustro conical inl~t and outlet sections to the drum are threaded.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
It is the objective of the present invention to provide a simplified mill structure that reduces the cost of the mill and overcomes many of the difficulties in the prior art joint construction.
Broadly, the present invention cornprises a substantially cylindrical drum rotatable about its longitudinal central axis on a pair o axially spaced trunnions, said drum comprising a cylindrical body portion of a first radial thickness, a pair of cylindrical ring portions concentric with said body portion and extending axially one from each axial end o~ the body portion, said ring portions have a radial thickness greater than the said first radial thickness, heads at opposite ends of said dru~, the axial end of each o~ said ring portions remote from said body portion being in a butting relationship wit~
said inner face of the adjacent one of said heads, connectin~ means space circumferentially about and extending through each of said heads and secured to the adjacent one of said ring portions to connect said ring portions to their respective adjacent heads, said trunnions being connected to and extending axially outward of said heads, each of said rims extending .
74~6~
~OK 103-089-A
from its adjacent head by a distance to accommodate peak stresses applied to said drum when said drum is loaded and rotated on said trunnions.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features, objects and advantages will be evident from the following detailed description of the preferrad embodiments of the present invention taken in conjunction with the accompanying drawings in which :
Figure 1 shows an axial section view of the top half of the mill incorporating the prPsent invention 7 Figure 2 illustrates a typical peak stress condition in the cylindrical drum section adjacent the head.
DESCRIPTION OF THE PREFER~ED EMBODIMENTS
As shown in Figure 1, the mill 10 comprises a substantially cylindrical drum section 12 composed of a drum or shell central portion 14 and a pair of end reinforcing rings 16. Only one shell portion has been shown but the section 12 may be composed of a plurality of axially aligned cylindrical portion~ 14 interco~nected at adjacent ends. Regardle~s of the number of central portions the rings 16 will only be provided adjacent each of the heads 18. Connected to each o~ these rings 16 i8 a head 18 which is provided with an axially extending trunnion 20 for rotatably mounting the drum or mill 10. The mill may be driven by any suitable drive means, in the illustrated arrangement a suitable r:lng gear generally indicated at 22 has been shown for this purpose.
The cylindrical drum at 12 as indicated is formed by at least one cylindrical shell portion 14 the ends of which each have welded thereto be suitable welds 24 a reinforcing ring 16. The distance between these welds 24, i.e. the axial length of the reinforcing elements of rings 16 as indicated by a letter x and must be a minimum length sufficient to contain the peak stresses that are generated in the drum structure 12 as the mill, supported by the trunnions 20 is rotated under load. Obviously these welds 24 will be suitably located so as not to interfere with bolting of the liners (not shown) to the shell. It will be apparent that by selecting a ring of sufficient axial extent, this may be achieved.
The typical stress curve showing stresses vs distance from the head is shown in Figure 20 It can be seen that adjacent to head maximum stresses are encountered whereas spaced from the head depending on the si~e of the mill, etc. a significantly reduced stress concentration is observed. This permits the use of thinner plate to fabricate those portions of the drum 12 operating under lower stress conditions.
5enerally the minimum distancP x will be at least 8 inches and preferably greater than about 12 inches, however x may be determined specifically for any given installation.
It is important that the reinforcing ring 16 be connected directly to the adjacent head 18, via a connection means extending substantially axially of the cylindrical drum 12, i.e. the xight angular connection and the complicated stress loading have been replaced by a substantially straight line connection extending axially of the drum.
Tn the illustrated arrangement the connection between the drum and head is obtained by a plurality of bolts 26 projecting through the head and threaded into the reinforcing rings 16~ Obviously the thickness of these rings must be ample to accommodate the size of bolts 26 used in securing the heads to the ~3'7~
drum section 12 but more important this increased thickness will be suficient to reduce the stress concentration ~o acceptable levels for the material used~
It will be noted that the welds 24 between the cylindrical body portion 12 and the rims 16 are spaced significantly (minimum distance xj from the end edges of the drum section 12, i.e. from the heads 18, Thi9 structure permits the use of automatic welding equipment to form these welds and thereby ensure that a relative uniform weld is obtained (as compared with manually welded joint) that was required with the right angle connection~
It will be further noted that the reinforcing area formed from plate material by appropriately curving the rol].ed faces of the plate material into cylindrical form and ~he ring i9 aligned with the cylindrical body section 12 and with the bolts or studs 26 so that the rolled surfaces of the plate material (delamination planes) with the direction of force transmis~ion between the heads 18 and the cylindrical drum 12 and the risk of delamination of the plate material is substantially eliminated.
By fabricating mill structure 10 as above described it has been ~ound that the inner drum or shell portion or portions 14 may be signifantly thinner than the thickness in the zone of the rein~orcing ring 16 whereby the cost of the mill may be significantly reduced, Modifications will be evident to those in the art without departing from the spirit of the invention as defined in ~he appended claims.
Claims (5)
1. A substantially cylindrical drum structure rotatable about its longitudinal central axis on a pair of spaced trunnions, said drum structure comprising a cylindrical shell portion having a first radial thickness, a pair of cylindrical reinforcing ring portions concentric with and connected to said shell portion and projecting axialy outward one from each axial end of said shell portion, said ring portions each having a radial thickness greater than said first radial thickness, heads at opposite ends of said rim structure, ends of said ring portions remote from said shell portion being in a butting relationship with an inner face of the adjacent one of said heads, connecting means spaced circumferentially about and extending through each of said heads and secured to the adjacent of said ring portions to connect each said ring portion to its adjacent said head, said trunnions being connected on to each of said heads and extending axially outwardly from said heads relative to said drum portion, each of said rings extending from its adjacent head by a distance sufficient to accommodate the peak stresses generated in said drum structure when said drum structure is loaded on said trunnions.
2. A drum structure as defined in Claim 1 wherein said shell is connected to said rings by circumferentially extending welds formed by automatic welding equipment.
3. A drum structure as defined in Claim 1 where it said connecting means extend through said head in a direction substantially parallel to central longitudinal axis.
4. A drum as defined in Claim 1 wherein said connecting means comprises a plurality of bolts extending through said head into a threaded engagement with threaded recesses in said rings, said bolts having their longitudinal axis extending substantially parallel to said axis of rotation.
5. A drum structure as defined in Claim 1, 2 or 3 wherein said distance is at least 8 inches.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000407482A CA1187060A (en) | 1982-07-16 | 1982-07-16 | Mill construction |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000407482A CA1187060A (en) | 1982-07-16 | 1982-07-16 | Mill construction |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1187060A true CA1187060A (en) | 1985-05-14 |
Family
ID=4123235
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000407482A Expired CA1187060A (en) | 1982-07-16 | 1982-07-16 | Mill construction |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1187060A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2606295A1 (en) * | 1986-05-02 | 1988-05-13 | Krupp Gmbh | CENTRIFUGAL DRUM FOR A FLAT BOTTOM CENTRIFUGAL MACHINE OPERATING IN A DISCONTINUOUS WAY |
-
1982
- 1982-07-16 CA CA000407482A patent/CA1187060A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2606295A1 (en) * | 1986-05-02 | 1988-05-13 | Krupp Gmbh | CENTRIFUGAL DRUM FOR A FLAT BOTTOM CENTRIFUGAL MACHINE OPERATING IN A DISCONTINUOUS WAY |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |