CA1186529A - Composite ring gear system - Google Patents

Composite ring gear system

Info

Publication number
CA1186529A
CA1186529A CA000406050A CA406050A CA1186529A CA 1186529 A CA1186529 A CA 1186529A CA 000406050 A CA000406050 A CA 000406050A CA 406050 A CA406050 A CA 406050A CA 1186529 A CA1186529 A CA 1186529A
Authority
CA
Canada
Prior art keywords
gear
segments
support
drum
brinell hardness
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
Application number
CA000406050A
Other languages
French (fr)
Inventor
Rhual L. Guerguerian
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dominion Engineering Works Ltd
Original Assignee
Dominion Engineering Works Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Dominion Engineering Works Ltd filed Critical Dominion Engineering Works Ltd
Priority to CA000406050A priority Critical patent/CA1186529A/en
Application granted granted Critical
Publication of CA1186529A publication Critical patent/CA1186529A/en
Expired legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H55/00Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02Toothed members; Worms
    • F16H55/12Toothed members; Worms with body or rim assembled out of detachable parts

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Gears, Cams (AREA)

Abstract

COMPOSITE RING GEAR SYSTEM
ABSTRACT OF THE DISCLOSURE
The composite ring gear structure, for driving heavily loaded drums in rotation about a horizontal axis thereby to tumble the material loading the drum, is formed by means of a plurality of gear support segments adapted to be connected in driving relation about the periphery of the drum and to be coupled together and extend 360° around the circumference of the drum to provide a gear support.
A plurality of gear segments are mounted on the outer periphery of the gear support to form a continuous ring gear extending completely about the gear support. The gear segments have a Brinell hardness of at least 250 and the gear support segments have a maximum Brinell hardness of 250 while always maintaining a minimum difference in Brinell hardness between the gear segments and the gear support of at least 50 Brinell hardness units so that the support segments are significantly more ductile than the gear segments thereby to dampen stress and impede transmission of stress between the drum and gear segments.

Description

-l- GOK 103-0~5 COMPOSITE RING GE~R SYSTEM
F~ELD OP TH~ INVENTION
The present invention relates to a composite gear structure. More particularly the present invention relates to a composite gear structure formed by a gear support mounting gear segments having significantly higher Brinell hardness than the support.
Grinding mill structures for grinding iron ore and the like are generally formed by relatively huge rotating drums carrying loads in the order of l,000,000 lbs. that shift as the mill rotates. Such mills are generally well over 30ft. in diameter and have enormous power requirements, particularly for start-up under load.
These mills are generally driven by a ring gear and pinion arrangement. The ring gears are larger in diameter than the drums (in the order of about 40 ft.). Current practice is to form these ring gears by casting integral gear segments (with sizes generally indictated by shipping clearances and foundry practices each having a rim onto which the teeth are formed and an integral supporting structure composed of a web projecting radially inwardly from the rim and terminating in a bolting flange and circumferentially spaced ribs projecting laterally from the web and extending from the rim to the adjacent side of the bolting flange. A plurality of GOK 103-0~5 --2~
such segments are bolted together -to form a ring gear that is connected generally by a circular arrangement of bolts extending through the bolting ~langes for attachment circumferentially about the drum of the mill.
The teeth are cut in the rim in the form of helical or double helical teeth and maybe with at least one pinion that is driven generally by an electric motor. These teeth must at least meet the American Gear Manufacturers Association (AGr`~) standards which in view of the heavy loads results in very cumbersome gears having extremely wide gear faces to accommodate the stresses imposed by the pinions.
Such large gears make machining difficult as the accuracy of the 40 ft. diameter gear must be maintained regardless of the face width. Furthermore such integral gear structures have been subject to failure Eor a variety of different reasons including, tooth weaknesses (teeth have been known to break o~f as a result of repeated bending stresses that may arise from overload), or misalignment conditions and stresses associated with poor surface finish or other material defects.
Failures have also occured from cracks progressing substantially radially through the web section and by cracks formed at the junction of the web with the bolting flange.
Considerations necessary for the design of proper structural support structure, i.e. web, rib and bolting flange structure and those required for gear face structure to withstand the wear factors resulting from the application of torque through the pinion, are significantly different. Furthermore the structural behavior of the drum imposes further stresses on the gear structure since the drum tends to deform as it is rotated whereas the ring structure which is more rigid tends to vigorously resist this de~ormation.

BRIEF DESCRIPTION OF THE PRESENT INVENTION
An object of the present invention is -to provide a composite ring gear structure having a gear surface of material harder than the material form.ing the support structure to permit the gear faces to withstand the deformations and the wear stresses applied by the pinion while the tougher more ductile support structure dampens transmission of stresses between the now even more rigid gear or rim structure (due to the use of harder material) and the drum and inhibits the initiation of stress cracks.
Broadly the present invention relates to a composite ring gear structure for driving a loaded drum for rotation about a longitudinal axis thereby to tumble material within the drum, said composite gear structure comprising a plurality of gear support segments adapted to be connected in driving relation to the drum and to be coupled together to extend 360 around the circumference of the drum and provide an annular gear support, a plurality of toothed gear rim segments secured to the outer periphery of said gear support to form a continuous ring gear rim extending the full circumference of said gear support, said gear rim segments having a Brinell hardness of at least 250 and said support segments having a maximum Brinell hardess of 250 with a minimum difference of Brinell hardess between said gear segments and said support segments of at least 50 Brinell hardness units so that said support segments are significantly more ductile than said gear segments thereby to dampen stress transmission between said rim and said gear segments.
BRIEF DESCRIPTION OF DRAWINGS
Further features, objects and advantages will be evident from the following detailed description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings in which:

_~_ Figure 1 - is a side elevation view of a composite gear structure constructed in accordance with the present invention.
Figure 2 - is a section on the line 2-2 of Figure l.
Figure 3 - is a partial section illustrating a modified version of the composite gear structure of the present invention connected in driving relation to a grinding mill.
Each composite gear segment 10 for forming a composite gear structure of the present invention is composed of a gear support segment 20 and at least one gear rim segment 22.
The support 20 comprises at least one radially or conically extending web 12 with a plurality circumferentially spaced axially extending radial ribs 14 positioned on opposite sides of the web 12 and/or between webs when more than one web is used. The ribs 16 at each end of the support segment 20 are relatively thicker and provide bolting flanges for connecting a pair of adjacent ones of said composite gear segments 10 together. The radial inner portion of the web 12 forms a bolting flange 18 and is provided with a plurality of bolt holes arranged on an arc of a circle and used for attaching a composite ring gear, formed from a plurality of segments 10 bolted together, to the mill as will be described hereinbelow.
A plurality of gear rim segments 22 are secured to the outer periphery of the support segment 20. Teeth are cut into these gear segments 22 to provide a rim section 24 and the teeth indicated at 26. The rim section 24 of each segment 22 is secured in a suitable manner to a support section 20. In the embodiment illustrated in Figures 1 and 2, this connection between the rims 24 and the support segment 20 is by a suitable welding which will extend along the ribs 14 and along the length of the web 12 a,s indicated at 21 in Figure 2. The structure shown in Figure 3 incorporates another form of support segment suitable for use with the instant invention. In this arrangement the rim segments 24 are secured to the modified support structure 20 by suitable bolts 28 extending through a rim plate 30 which is moulded as an integral part of the support structure 20.
The teeth 26 may be machined on each of the segments 22 preferably by pre-assembling a ring gear by connecting together a requisite number of support segments 20 to form the circular support ring structure and securing the segments 22 thereto to form a 360~ gear blank into which the teeth 26 are -then cut. Alternatively each of the gear segments 22 may be cut individually and assembled onto the supporting ring structure formed from segments 20.
The composite gear formed from the segments 10 is bolted to the mill structure indica-ted at 32 by a circular arrangement of bolts 34 extending -through bolting flange 18, the head 36 closing the drum 40 and the flange 38 at the adjacent end of the drum structure 40. A suitable trunnion 42 extends axially from the head 36 to provide a bearing upon which -the mill 32 is rotated (a similar head and trunnion is provided at the opposite end of the mill but normally only one ring gear will be provided).
Materials from which the gear segments 22 and the support segments 20 are constructed are extremely important since each encounters significantly differently stress conditions.
The gear segments 22 from which the teeth 26 are cut must be able to withstand the gear loading or tooth loading applied by the pinions (not shown) driving the mill 32. This requires relatively hard material. Such material does not easily bend and is generally more brittle so that when bending stresses are applied to deform annular rim, the rim does not deflect significantly and if too high a stress is applied it will simply abruptly fail. This hardness is however essential if the required tooth strengths are to be provided on gears of reasonable size.
I'he support member on the other hand transmits the torque applied to it by the gear segments 22 and delivers this torque to the drum ~0 to rotate the mill, i.e. this element 20 provides the driving link between the relatively rigid ring formed by joining a plurality of the relatively hard gear segments 22. The ring gear so formed is obviously of a diameter larger than the drum and provides a relatively difficultly deformable ring extending circumferentially about the mill.
The drum and head structure formed by the heads 36 (only one shown) and drum ~0 tends to deflect significantly as the loaded mill 32 is rotated on the trunnions 42 (only one shown). This loading tends to distort the circumferential arrangement of the bolts 34 holding the drum 40, head 36 and ring gear structure together, axially and to some extent radially while the ring formed by the gear segments 22 tends to remain substantially undeformed and retain its right cylindrical shape due to its greater stiffness or hardness, i.e. the ring gear formed by the segments 22 has less latitude for deflection than the mill. The support structure 20 of the present invention must be made more ductile than the gear to be able to accommodate the different degrees oE
deflections of the mill and ring gears and reduce the transmission of stresses between the drum or mill structure 32 and the ring gear formed by the segments 22.

That the radial depth of the support segments, i.e. the distance between the bolting flange 18 and the periphera~ surface to which the rims 24 are connected should be no greater than -twice the face wid-th of the teeth, i.e. axial length of the teeth and generally not less than one half this face wid-th.
Thus the support structure 20 must be capable of absorbing a significant amount of the stresses applied to the ring by deformation of the head 36 and drum ~0 in a relatively short radial length and still being capable of transmitting the torque necessary to rotate the drum.
It has been found that -the Brinell hardness of support segments 20 which are normally cast structures formed from cast steel, should not exceed about 250 Brinell hardness and generally will be in the range of about 210-1~0 Brinell hardness.
The gear teeth on the other hand must be relatively less ductile, i.e. have a significantly high Brinell hardness to withstand the wear and stresses imparted to it from the drive pinion. The gear segments 22 are also made of steel and will have hardness above 250 Brinell hardness and preferably above 265, while support segments 20 will have a Brinell hardness in the range of 150-250, preferably about 180-210.
It is contemplated that if the gear segments are to exceed 380 Brinell hardness special care must be taken for adequately damping out the drum deflection, i.e. the radial depth of the segments 20 may have to be increased. The hardness of the gear segments 22 must be properly co-ordinated with the hardness of the support segments 20 to obtain the benefits of the present invention. There should be at least a difference in Brinell hardness of 50 between the gear segments 22 and the support segments 20 to d ~

_g _ provide significant differences in ductibilit~ between these elements.
The gear segments and suport segments are both made of steel one having different strength (toughness, hardness, ductility etc.) characteristics than the other as defined by the differences in Brinell hardness. If materials other than steel are used they must have the equivalent relevant characteristics of steel having the above defined hardness. It will be apparent that the thickness of the memhers will change their relevant stiffness and/or apprent ductility and the above hardness characteristics are given for conventionally designed gears i.e. having the normal thickness that would be used in designing the gear structure. If these thicknesses are changed significantly the benefit of the present invention will not be attained unless sufEicient ductility is built into the support segments by other means.
Modifications may be mad~ without departing from the spirit of the invention as defined in the appended claimsO

Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A grinding mill structure comprising a drum mounted for rotation about the longitudinal axis thereof thereby in use to grind material loaded within the drum by a tumbling action, a composite ring gear structure comprising a plurality of gear support segments adapted to be connected in driving relation with said drum and to be coupled together to extend 360° around the circumference of said drum to provide an annular year support, a plurality of gear segments secured to the outer periphery of said gear support to form a continuous ring gear extending the full circumference of said gear support, said gear segments having relevant strength properties equivalent to the relevant strength properties of steel having a Brinell hardness of at least 250 and said support segments having relevant strength properties equivalent to the relevant strength properties of steel having a maximum Brinell hardness of 250 with a minimum difference in Brinell hardness between said gear segments and support segments of at least 50 Brinell hardness units so that said support segments are significantly more ductile than said gear segments thereby to dampen stress transmission between said drum and said gear segments.
2. A grinding mill structure as defined in Claim 1 wherein said support segments have a Brinell hardness in the range of 150-225.
3. A grinding mill structure as defined in Claim 1 wherein said support segments have a Brinell hardness in the range of 180-210.
4. A grinding mill structure as defined in Claim 1, 2 or 3 wherein said gear segments have a Brinell hardness of at least 265.
5. A grinding mill structure as defined in Claim 1, 2 or 3 wherein said gear segments have a Brinell hardness in the range of 265-380.
6. A grinding mill structure as defined in Claim 1, 2 or 3 wherein said support segments and said gear segments are made of steel.
CA000406050A 1982-06-25 1982-06-25 Composite ring gear system Expired CA1186529A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000406050A CA1186529A (en) 1982-06-25 1982-06-25 Composite ring gear system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000406050A CA1186529A (en) 1982-06-25 1982-06-25 Composite ring gear system

Publications (1)

Publication Number Publication Date
CA1186529A true CA1186529A (en) 1985-05-07

Family

ID=4123103

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000406050A Expired CA1186529A (en) 1982-06-25 1982-06-25 Composite ring gear system

Country Status (1)

Country Link
CA (1) CA1186529A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017069626A1 (en) * 2015-10-23 2017-04-27 Holwegen Tilburg B.V. Method for manufacturing at least a part of a ring gear, and ring gear
WO2017069625A1 (en) * 2015-10-23 2017-04-27 Holwegen Tilburg B.V. Method for manufacturing at least a part of a ring gear, and ring gear

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017069626A1 (en) * 2015-10-23 2017-04-27 Holwegen Tilburg B.V. Method for manufacturing at least a part of a ring gear, and ring gear
WO2017069625A1 (en) * 2015-10-23 2017-04-27 Holwegen Tilburg B.V. Method for manufacturing at least a part of a ring gear, and ring gear
NL2015647B1 (en) * 2015-10-23 2017-05-11 Holwegen Tilburg B V Method for manufacturing at least a part of a gear ring, and tooth ring.
NL2015648B1 (en) * 2015-10-23 2017-05-11 Holwegen Tilburg B V Method for manufacturing at least a part of a gear ring, and tooth ring.

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