GB2123315A

GB2123315A - Bowl-mill drive

Info

Publication number: GB2123315A
Application number: GB08318759A
Authority: GB
Inventors: Franz Toggweiler
Original assignee: Maag Gear Wheel and Machine Co Ltd; Maag Zahnrader und Maschinen AG
Current assignee: Maag Gear Wheel and Machine Co Ltd; Maag Zahnrader und Maschinen AG
Priority date: 1982-07-12
Filing date: 1983-07-11
Publication date: 1984-02-01
Also published as: DK314783A; IT8321860A0; DE3232394C2; JPS5922660A; IT8321860A1; DE3232394A1; DK314783D0; GB8318759D0; GB2123315B; FR2529806A1; IT1163628B

Abstract

A receiving plate (22) with a vertical axis of rotation (24) for a grinding bowl (91) is mounted on a housing (10,20) through a thrust bearing (26) and a radial bearing (28) which take up grinding forces acting on the bowl (91) in operation. The receiving plate (22) is additionally connected to the housing (10,20) by a counter-pressure bearing which prevents the plate from being lifted from the housing. The receiving plate is driven through an epicyclic gear (50) which is coaxial therewith and which comprises a satellite carrier (62) secured to the receiving plate (22) and an outer central wheel (64) which is secured to the lower housing portion (10) and which carries the thrust bearing (26). The counter-pressure bearing (27) is formed from a shoulder (87) formed on the satellite carrier (62) and a collar (89) formed on the outer central wheel (64) and which engages over the shoulder (87). <IMAGE>

Description

SPECIFICATION Bowl-mill drive The invention relates to bowl-mills or pan grinders and in particular to bowl-mill drive gears.

A bowl-mill drive gear the subject of our earlier British application GB 2 108 864A, comprises a housing on which a grinding bowl receiving plate is mounted on a vertical axis of rotation through bearing means comprising a thrust bearing and a radial bearing which take up grinding forces acting on the grinding bowl in operation. The housing comprises a lower portion and an upper portion secured thereto on which the receiving plate is mounted. The receiving plate is driven through a mitre gear disposed in the lower housing portion and an epicyclic gear. The epicyclic gear has an outer central wheel which is disposed as a component of the upper housing portion on the lower housing portion and supports the thrust bearing and the radial bearing for the receiving plate. The forces taken up by the thrust bearing are transmitted downwards through the annular outer central wheel.

Despite the considerable loading of the outer central wheel, the contact pattern of the teeth of the epicyclic gear remains practically uninfluenced by the axial forces appearing in operation of the mill because bending moments which could deform the outer central wheel and consequently impairthe contact patterns of the teeth are at least largely avoided. At the same time, the manufacturing costs for the upper housing portion can be kept low because the annular outer central wheel itself forms an important component of the upper housing portion.

In the said drive gear as in other previously known bowl-mill drive gears, in addition to the substantially axial grinding forces appearing in operation, in special cases strongly eccentric additional forces may appear which can result from the fact that one of a plurality of grinding rolls working in the grinding bowl runs onto a particularly hard object which cannot be crushed or at least not immediately. Thus it has already happened that a broken off excavator tooth of high-strength steel has got into a grinding bowl together with stone chippings which were to be ground. In such cases, in addition to a static, substantially axial load of the order of magnitude of 300 t for example, which can be taken into consideration by computation, a sudden eccentric load of 600 t may occur which can act eccentrically to such an extent that its line of action lies outside the thrust bearing.In such a case, a brief tilting movement may occur about a point situated at the outer edge of the thrust bearing. Consequently, the parts of the thrust bearing sliding on one another gape apart in a wedge shape during a short period of time of the order of magnitude of a few fractions of a second and then close together again. This brief event, which generally does not disturb operation of the mill and generally even remains unnoticed, can nevertheless cause damage to the thrust bearing and possibly also to the radial bearing.

According to the present invention, there is pro vided a bowl-mill drive gear with a housing on which a receiver with a vertical axis of rotation for a grinding bowl is mounted via a thrust bearing and a radial bearing to take up grinding forces acting on the grinding bowl in operation, the receiver being additionally connected to the housing through a counter-pressure bearing which restrains the receiv er from being lifted from the housing.

Lifting, within the meaning of the invention, is to be understood to mean a separation of the parts of the thrust bearing sliding on one another endanger ing the thrust bearing. in order to prevent such separation, the counter-pressure bearing according to the invention does not need to be free of play; on the contrary, it is an advantage to provide a bearing clearance of the order of magnitude of a few tenths of millimetres up to about one millimetre, so that the bearing surfaces can be adequately lubricated.

The invention is preferably applied in a bowl-mill drive gear wherein, in accordance with the drive gear described in application GB 2 108 864 the housing comprises a lower housing portion and an upper housing portion secured thereto and the receiver can be driven by an epicyclic gear which is coaxial therewith and which comprises a satellite carrier secured to the receiver and an outer central wheel secured to the upper housing portion and carrying the thrust bearing.

For such a bowl-mill drive gear, the present invention is preferably further developed in that the counter-pressure bearing comprises a shoulder formed on the satellite carrier and a collar formed on the outer central wheel and which engages over the shoulder. This has the advantage that the outer central wheel serves several different functions, namely as a component of the epicyclic gear as well as a component of the housing and as such carries not only the thrust bearing and the radial bearing but also the counter-pressure bearing.

One embodiment of the invention is described in more detail below by way of example with reference to the accompanying diagrammatic drawing in which shows a vertical axial section through a bowl-mill drive gear according to the invention.

The bowl-mill drive gear illustrated has a lower housing portion 10 with a bottom plate 12 and a cylindrical housing wall 14 which comprises a lateral opening closed by a cover 16, and it ends in a flange 18 at the top. The drive gearfurther has an upper housing portion 20 on which a receiving plate 22 is mounted for rotation about a vertical axis of rotation 24 by means of a thrust bearing 26, a counterpressure thrust bearing 27 and a radial bearing 28.

Disposed in the lower housing portion 10 is a mitre gear 30 which is constructed in the form of a bevel gear in the example illustrated. The gear 30 has a horizontal drive shaft 32 which projects to the outside through the cover 16 with radial clearance but is sealed and can be coupled to a drive motor not illustrated. A bevel pinion 34 on the inner end of the drive shaft 32 meshes with a plate-shaped bevelgear wheel 36 which is secured to a vertical driven shaft 38 coaxial with the axis of rotation 24. The gear 30 has a common base 40 for a bearing 42 in which the drive shaft 32 is mounted and for a bearing 44 in which the bevel-gear wheel 36 and the driven shaft 38 are mounted and supported from below. At the upper end of the driven shaft 38 are a pivot 46 which has a spherical top face and outer coupling teeth 48.

Disposed above the mitre gear 30 is an epicyclic gear 50. This comprises a sun wheel 52 which is disposed coaxially with the vertical axis of rotation 24 and has a pivot 54 projecting downwards which is plane at its underside and is supported on the spherical face of the pivot 46. Associated with the pivot 54 are likewise external coupling teeth 56 which are connected to the coupling teeth 48 through an internally toothed coupling sleeve 58.

The coupling sleeve 58 is supported on the coupling teeth 48 of the driven shaft 38 against axial displacement downwards.

The sun wheel 52 meshes with three planet wheels 60 which are mounted with uniform angular spacing on a satellite carrier 62. All the planet wheels 60, only one of which is illustrated, mesh with an internally toothed, annular outer central wheel 64 which rests on an annular supporting surface 66 constructed at the top of the flange 18 and is secured to this flange by screws 67. The annular supporting surface 66 is narrow in its radial dimension and the screws 67, which are only indicated in the drawing between the lower housing portion 10 and the outer central wheel 64, are made flexible as expansion screws.

The mean diameter D66 of the annular supporting surface 66 is identical with the mean diameter of the housing wall 14. The outer central wheel 64 has a mean diameter D64 which coincides with the mean diameter D26 of the thrust bearing 26 and the mean diameter D66 of the supporting surface 66.

The upper end face of the annular outer central wheel 64 has a central annular groove 68 machined in it which receives a lower thrust ring 70. Formed inwardly of this, on the central wheel 64, is an inner annular shoulder 72 on which a retaining ring 74 is supported and centred. The retaining ring 74 in turn supports and centres the radial bearing 28. The central wheel 64 also has an outer annular shoulder 76 formed on it which supports and centres a sealing collar 78. The rotary receiving plate 22 is sealed against the sealing collar 78 which is stationary.

The thrust bearing 26 comprises an upper bearing ring 80 which is secured to the receiving plate 22 and an upper thrust ring 82 which rests for tilting on the lower thrust ring 70 and is embedded in a lower bearing ring 84 on which the upper bearing ring 80 rests for sliding.

Furthermore, screwed to the underside of the receiving plate 22 is a bearing rim 86 which is mounted in the radial bearing 28 and to which the satellite carrier 62 is secured.

The counter-pressure bearing 27 comprises a shoulder 87 which is formed on the satellite carrier 62 and a collar 89 which is formed on the outer central wheel 64 and engages over the shoulder 87.

Shoulder 87 and collar 89 have bearing surfaces which are coated with bearing metal and are situated opposite one another, in normal operation, with an axial spacing of a few tenths of millimetres.

The receiving plate 22 is constructed, in the usual manner, to receive and centre a grinding bowl 91 which comprises, on its upper face, an annular runway 93 for grinding rolls (not illustrated). If one of these grinding rolls rolls over a hard objectwhich it cannot crush, then in addition to the normal grinding forces with a resultant along the axis of rotation 24, an additional force, for example in the direction of the arrow 95, can act on the grinding bowl 91 and from this on the receiving plate 22. Because of its great eccentricity, this additional force tends to tilt the receiving plate 22, for example about the point 97. Such tilting is prevented, however, by the thrust counter-pressure bearing 27.

The outer central wheel 64 thus fulfills a fivefold task: a) As a component of the epicyclic gear 50, the outer central wheel participates in the transmission of the drive power to the receiving plate 22.

b) In addition, the outer central wheel takes up the axial loading of the receiving plate 22 through the thrust bearing 26 and transmits it to the lower housing portion 10 without bending moments occurring.

c) Apart from this, the outer central wheel prevents, with its collar 89 forming part of the counterpressure bearing 27, tilting of the receiving plate 22.

d) Furthermore, the outer central wheel is a component of the upper housing portion 20 which is important for the protection of the epicyclic gear 50 and of the counter-pressure bearing 27.

e) Finally, the outer central wheel 64 supports and centres the radial bearing 28.

The bowl-mill drive gear described is assembled in such a manner that first the mitre gear 30 is inserted in the lower housing portion 10. Then the satellite carrier 62 with the sun wheel 52 installed is lowered onto supports which can be secured to the housing wall 14. The sun wheel 52 is coupled to the drive shaft 38 of the mitre gear 30 by means of the coupling sleeve 58. Then the outer central wheel 64 is pushed over the teeth of the planet wheels 10, lowered onto the lower housing portion 10 and screwed to this. Next the upper components, which are carried by the outer central wheel 64, are lowered onto this and finally the receiving plate 22 is screwed to the bearing rim 86, during which the satellite carrier 62, dependent from the bearing rim 86, is pulled upwards, is lifted from the supports mentioned as a result and at the same time the necessary bearing play of the counter-pressure bearing is adjusted.

Claims

1. A bowl-mill drive gear with a housing on which a receiver with a vertical axis of rotation for a grinding bowl is mounted via a thrust bearing and a radial bearing to take up grinding forces acting on the grinding bowl in operation, the receiver being additionally connected to the housing through a counter-pressure bearing which restrains the receiverfrom being lifted from the housing.

2. A bowl-mill drive gear as claimed in claim 1, wherein the housing comprises upper and lower housing portions secured together and the receiver is arranged to be driven through an epicyclic gear which is coaxial therewith and which comprises a satellite carrier secured to the receiver and an outer central wheel which is secured to the lower housing portion and which carries said thrust bearing, the counter-pressure bearing comprising a shoulder formed on the satellite carrier and a collar formed on the outer central wheel and which engages over the shoulder.

3. A bowl-mill drive gear constructed and arranged for use and operation substantially as described herein with reference to the accompany ing drawing.