GB2049075A - Transmission gear arrangement - Google Patents

Abstract

A transmission gear arrangement comprising a gear box 11 with main input shaft 13, a main gearing 12 within the gear box with an output shaft 20 for driving a rotatable member, for example a sprocket wheel of a scraper chain conveyor, and a worm-gearing 22 also within the gear box. The worm-gearing, which can be engaged with the main gearing by a clutch sleeve 23 for driving the rotatable member and which can be disengaged therefrom, constitutes auxiliary drive means suitable for tensioning the chain or chains of the conveyor and is so arranged as to add little to the overall size of the gear box. <IMAGE>

Description

SPECIFICATION Transmission gear arrangement This invention relates to a transmission gear arrangement and will be described by way of example only, with reference to its use with a scraper chain conveyor of the kind used in coal mines.

In the assembly of a scraper chain conveyor it is necessary, after the chain or chains have been laid in the upper run and the lower run of the conveyor line pans, to take all the slack from the chain or chains and, preferably, to give some initial tension to it or them before connecting one end of a chain to the other end of the chain. After a period of operation of a scraper chain conveyor, it may be necessary to remove some of the chain, for the purpose of countering an increase in length of the chain due to wear and to stretching, and then to connect the ends of the remaining chain.

Devices which perform these functions are known as "chain tensioners".

A scraper chain conveyor is, customarily, driven by a driving motor which is connected to a sprocket wheel (for the chain or chains) by way of a mechanical clutch or a fluid-coupling and a main gearing housed in a gear box.

Recent chain tensioners are powered independently of the conveyor driving motor and drive the chain, or chains, for tensioning thereof, through not only the existing main gearing but also an auxiliary gearing so that the overall gear ratio is much greater than that of the main gearing alone. This means that the ends of a chain can be brought together very slowly when the independent power source is operated and the conveyor or driving motor is not operative to drive the main gearing.

These recent chain tensioners have been separate from, and have to be attached externally of, the gear box. For instance, one such chain tensioner has used spur gearing, as the auxiliary gearing, within a box which is separate from and is sandwiched between a fluid coupling and the gear box. An independent power source is mounted externally of the box housing the spur gearing so that it can drive the latter whenever necessary.

Ail the recent chain tensioners, even without their independent power sources, substantially add to the overall dimensions of the gear box and the equipment normally associated with it, e.g.

fluid-coupling or clutch, and this is a disadvantage when the scraper chain conveyor is used in a coal mine where the available space for the conveyor driving means is small.

The invention is intended to provide a gear bos with an auxiliary gearing which adds little to the overall size of the gear box, and which is suitable for chain tensioning.

According to the invention, a transmission gear arrangement comprises a gear box, a main gearing within the gear box for driving rotatable member, and a worm gearing also within the gear box which can be engaged with the main gearing for driving the rotatable member and disengaged therefrom.

One way of carrying out the invention is described below with reference to drawings which illustrate only one specific embodiment, in which: Figure 1 is a cross-section taken through one end portion of a transmission gear arrangement, Figure 2 is a broken cross-section taken along the line Il--Il on Figure 1, Figure 3 is a partial cross-secticn also taken along the line Il-Il on Figure 1, but with certain components of the arrangement in a different operating position, and, Figure 4 is a view taken in the direction of the arrow IV on Figure 1.

The figures illustrate a transmission gear arrangement which includes a gear box 11 having a main reduction gearing, shown diagrammatically at 12, therein. The main reduction gearing is driven by way of a fluid coupling from a main driving motor, both in part generally indicated at M, through an input shaft 13. The gearing comprises a bevel pinion 14, fast with that shaft, which meshes with a crown wheel 15, and a small spur gear 16 is keyed to the same haft 17 as carries the crown wheel. The gear 1 6 meshes with a larger spur gear 1 8 itself mounted on a further shaft (not shown) parallel with the shaft 17. A further small spur gear (not shown), which is keyed to the further shaft, meshes with a larger spur gear 1 9 which is keyed to a shaft 20.This shaft, which is parallel with the shaft 1 7 and the further shaft (not shown) extends to the exterior of the gear box and forms the output shaft thereof.

As such, it is adapted to be connected to the sprocket wheel or wheeis (not shown) of the chain or chains of an associated scrap zr chain conveyor.

In this embodiment it is intended that the main driving motor is an electric motor.

Surrounding the input shaft 13 and co-axial therewith is the worm wheel 21 of a wormgearing 22. The worm wheel can be selectively connected to the input shaft and disconnected therefrom by a member 23 which surrounds a sleeve 24 fast with the input shaft. The member 23 is axially slidable upon the sleeve and thus with respect to the shaft. The member is generally of cylindrical form, being externally splined at 25 and internally splined at 26. To facilitate the axial sliding of the member 23 the splines 25 permanently engage with elongate splines 27 on the exterior surface of the sleeve 24 fast with the input shaft 13.

The external splines 25 are capable of engaging with internal splines 28 formed on the inside surface 29 of the worm wheel 21 when that is desired. For that purpose, the member 23 can slide, against the effort of coil spring 30 and with respect to the splines 27 on the sleeve 24, from a position in which the external splines 25 are not in engagement with the internal splines 28 of the worm wheel (as shown in Figure 2) to a position in which they are in engagement therewith (as shown in Figure 3), and vice versa.

Sliding of the member 23 is effected by the operation of a hand control lever 31 which is provided externally of the gear box 1 1 and which is fast upon a shaft 32. This shaft passes into the gearbox as shown and at its inner end is provided with a drive formation 33 which engages an annular recess 34 in the member 23. Rotation of the shaft 32 about its axis effects axial sliding movement of the member 23 thus to cause engagement of the drive from the worm wheel 21 to the shaft 13 or alternatively disengagement of that drive, as required.

The worm wheel 21 is in constant meshing engagement with the worm 35, disposed within the gear box, of the worm-gearing 22. The shaft 36 of the worm is supported for rotation by way of adapters 37 and 38 in bearings 39 and 40. The adapter 38 at that end of the shaft 36 to the right in Figure 1 projects through a suitable opening 41 in the wall 42 of the gear box and has a splined socket portion 43 through which the shaft 36 and worm 35 can be driven, when desired, to tension the chain or chains of the associated scraper chain conveyor, by a source of auxiliary power. In this embodiment such a source comprises an hydraulic motor 44 which has a splined output shaft 45 engageable with the socket portion 43 of the adapter 38.

When, as shown in Figure 3, the worm-gearing 22 is engaged with the input shaft 1 3 and is driven by the source of auxiliary power, the output shaft 20 of the gear box 11 will be driven by way of an auxiliary gearing (the worm-gearing 22) and the main reduction gearing 12, which together provide a greater overall reduction ratio than that of the main reduction gearing alone. This enables the chain or chains of the conveyor suitably to be tensioned.

As a safety measure, in order to lock the drive to the output shaft of the gear box if the source of auxiliary power should fail, the worm 35 maybe automatically locked in position immediately upon the occurrence of such failure. To provide for this the adapter 37 carries, fast therewith, an externally-toothed gear 46 disposed outside of the wall 47 of the gear box but enclosed in a subsidiary casing 48. The gear 46 is engageable by a plunger 49 which is so urged by a coil spring 50, that its head portion 51, which is provided with teeth of complementary shape to those of the gear 46, is biassed into locking engagement with that gear.However, when the hydraulic motor 44 is supplying power to the worm 35, liquid under pressure for driving the motor which is also applied to the plunger 49 overcomes the effort of the coil spring 50 and causes the plunger to move out of engagement with the teeth of the gear 46.

If the liquid pressure drops to a value at which the motor 44 is not driven, the spring 50 will urge the plunger into engagement with the teeth of the gear 46, and so prevent the thus-far tensioned conveyor chain from running back, hence avoiding otherwise possible danger to nearby equipment and personnel.

It is essential that the main driving motor for the conveyor be not operating or at least be disconnected from the main reduction gearing 12, when the auxiliary source of power is used for chain tensioning. To that end, movement of the hand control lever 31, to cause engagement of the external splines 25 of the axially-slidable member 23 with the internal splines 28 of the worm wheel 21 can also cause the main driving motor M to stop operating or cause it to be disconnected, for example by operating upon a mechanical clutch (not shown), from the main reduction gearing. It will remain stopped or disconnected until the hand control lever 31 is moved to disengage the wormgearing 22 from the input shaft 1 3.

One convenient way of stopping the electric main driving motor of this embodiment is by making movement of the hand control lever 31 actuate a suitable cam 52 to open or to close the contacts of a micro-switch 53 disposed in the electrical supply circuit 54 to the motor, the cam being suitably connected to the lever.

By using worm-gearing 22 within the gear box 11 several advantages are gained. First, the range of overall reduction ratios is greater than can be achieved by the spur gearing of prior chain tensioners. Second, it is possible to reduce the overall size of the equipment. Third, even the addition of an auxiliary source or power need not cause any increase, or substantial increase, in the overall envelope of the gear box and the equipment normally associated with it. Fourth, the gear box can be offered for sale without the wormgearing and the latter can be added, if later required, without adding to the size of the gear box.

It is to be understood that not all the various integers hereinbefore mentioned are essential for the transmission gear arrangement and that they can be replaced by other suitable integers.

The auxiliary motor and gearing above described can be used to effect slow running of the conveyor in the event that it becomes partially jammed making it otherwise difficult to re-start.

Operation of the auxiliary motor and gearing then causes such inching of the conveyor as will effect clearing of the jammed conveyor and thereby facilitate re-starting.

Although in the embodiment above-described with reference to the drawings the output shaft of the gear box is adapted to be connected to a rotatable member in the form of a sprocket wheel of a scraper chain conveyor, the invention is in no way limited to such application as in other embodiments the invention may with advantage be applied to equipment having other forms of rotatable member required to be driven by way of a gear box likewise including auxiliary gearing.

Claims (15)

1. A transmission gear arrangement comprising a gear box, a main gearing within the gear box for driving a rotatable member, and a worm-gearing also within the gear box which can be engaged with the main gearing for driving the rotatable member and disengaged therefrom.

2. An arrangement as claimed in Claim 1, wherein the worm wheel of said worm-gearing surrounds and is coaxial with the input shaft of said main gearing.

3. An arrangement as claimed in Claim 2, wherein a member, which is externally splined and which is so internally splined as to be axially slidable with respect to said input shaft, affords selective connection of said worm wheel to said input shaft and disconnection therefrom.

4. An arrangement as claimed in any one of the preceding claims, wherein the worm of said worm-gearing is adapted to be driven, through a suitable opening provided in the wall of the gear box, by a source of auxiliary power.

5. An arrangement as claimed in Claim 4, wherein said source of auxiliary power comprises an hydraulic motor adapted for fitment to said wall of said gear box.

6. An arrangement as claimed in either Claim 4 or Claim 5, wherein means are provided which are operable automatically to lock said worm in position in the event that said source of auxiliary power fails.

7. An arrangement as claimed in Claim 6, wherein the locking effect by the engagement of a spring-urged plunger with an element fast with one end portion of said worm.

8. An arrangement as claimed in Claim 7, wherein said element comprises an externallytoothed gear, and said spring-urged plunger has a head portion of suitable toothed shape for engagement with the teeth of said gear.

9. An arrangement as claimed in any one of Claims 2 to 8, wherein said input shaft carries a bevel pinion which meshes with a crown wheel, said pinion and crown wheel forming part of said main gearing.

10. An arrangement as claimed in Claim 9, wherein said main gearing also includes spur gearing between said crown wheel and the output shaft of said gear box.

1 An arrangement as claimed in Claim 10, wherein said output shaft is parallel, or substantially so, to the shafting of said crown wheel and spur gearing, and said output shaft and shafting are disposed at right-angles, or substantially so, to the axis of said input shaft.

12. An arrangement as claimed in any one of Claims 3 to 11, wherein a control lever, for effecting sliding movement of said externally and internally splined member, is provided externally upon the gear box.

13. An arrangement as claimed in Claim 12, wherein control means are provided in association with said control lever for bringing a main driving motor for said gear box into and out of operation in dependence upon the positioning of that lever.

14. An arrangement as claimed in Claim 13, wherein said main driving motor is an electric motor.

15. An arrangement as claimed in Claim 14, wherein said control means includes a camoperated switch provided in the electric supply circuit to said motor, the cam of said switch being connected with said control lever.

1 6. A transmission gear arrangement substantially as hereinbefore described with reference to the accompanying drawings.