GB2157241A

GB2157241A - Improvements in or relating to rack railway locomotive drive transmission

Info

Publication number: GB2157241A
Application number: GB08409246A
Authority: GB
Inventors: Christopher Lunnon
Original assignee: Coal Industry Patents Ltd
Current assignee: Coal Industry Patents Ltd
Priority date: 1984-04-10
Filing date: 1984-04-10
Publication date: 1985-10-23
Also published as: GB8409246D0; DE3512792A1

Abstract

On narrow gauge locomotives having combined rack and wheel adhesion drive transmission, incorporating a rack-pinion gear (14), wheels (5 and 6) on a common axle (2), provision is made for driving the pinion gear (14) at a suitable speed for steep, rack-worked gradients, and for driving the wheels (5 and 6) at a higher speed for easy, wheel adhesion-worked gradients wherein an epicyclic gear comprising a sun gear (21), planet gears (17 and 20), a carrier, itself comprising a hub (1) and idler shafts (15 and 16), and an annulus gear (22), operates from the between the hub (1) and the axle (2) to give a step-up ratio from the hub (1)to the axle (2). With a bond brake (23) engaged, drive is transmitted via the epicyclic gear from the gear (13) to the wheels (5 and 6). When the brake (23) is inoperative drive is from the gear (13) to the brake-pinion year (14) only. <IMAGE>

Description

SPECIFICATION Improvements in or relating to locomotive drive transmissions This invention relates to improvements in locomotive drive transmissions. In particular this invention relates to improvements in combined rack and wheel adhesion locomotive transmissions such as are used for example, on narrow gauge railways in mines.

In coal mines it is common practice to provide narrow gauge railway networks to transport men, equipment, coal etc about the mine. As many mineworkings are not level due, for example, to strata movement and non-level coal measures, it is necessary to provide narrow gauge railway locomotives with drive means other than the usual wheel adhesion - many gradients experienced in mineworkings are too steep for simple wheel adhesion to operate adequately. To solve this problem rack and pinion drive has been extensively used within mines.

Usually known as a "rack" railway, this system operates by the locomotive's engine driving a pinion gear located underneath the locomotive which meshes with a static rack gear that lies parallel with and, usually, between the rails. This results in a very positive, slip free drive between the locomotive and the rack, thus allowing the locomotive to negotiate gradients much steeper than those a wheel adhesion transmission system allows. To optimise efficiency locomotives have been developed incorporating a hybrid rack/wheel adhesion drive system thus on relatively level sections of track there is no rack and the locomotive drives on wheel adhesion only. On gradients a rack is provided and the locomotive may drive via a rack-pinion gear onto the rack. Due to the restricted size of mineworkings the locomotives are designed to be as compact as possible.To obviate the effects of suspension spring movement, the mounting of rack-pinion gears on the wheel axle is common practice. Except where there are completely separate drives to rack-pinion and to wheels, there is provided a clutch between the pinion gear and the axle. In use on rack sections of the track, the clutch is disengaged; input drive from the locomotive's engine going to the rack-gear pinion only. On non-rack (wheel adhesion) sections of the track, the clutch is engaged; input drive from the locomotive's engine going to the wheels via the gear pinion, clutch and axle.The clutch is necessary because the pitch circle diameter of the gear pinion is normally different to the wheel diameter thus, were there no clutch, the transmission of drive on rack sections of the track would go via the gear pinion and wheels at different effective speeds causing undue power wastage and gear and wear to the wheels and rails, It is a well established requirement for locomotives of fixed horsepower which have to work on rail networks using rack and whee; adhesion sections, that the speed on the steep gradients, where rack drive is used, has to be considerably slower than that on easy gradients where wheel adhesion drive is appropriate.A shortcoming with narrow gauge locomotives, as described above having the convenient and compact arrangement of the pinion gear running on the wheel axle with a clutch between, drive going to the gear pinion, is that the pitch circle diameter of the rack-pinion gear is only slightly different from the wheel diameter, thus for a locomotive of given horsepower, the tractive effort that can be applied to the rack and pinion drive is too low.

What is needed is some means of driving the pinion gear at a much lower speed than the drive to the wheels to give an effective low gearing ratio.

An object of the present invention is to overcome in part the disadvantages of existing locomotive drive transmissions to produce an improved performance.

Accordingly the present invention provides a locomotive drive transmission arrangement, comprising an axle mounted between (and fixed to) a pair of wheels having rotatably mounted thereon a pinion gear arrangement including; - a first gear member, a second gear member spaced along the axle from the first gear member, and an epicyclic gear having associated therewith brake means, the arrangement being such that in a first condition, with the brake means inoperative, input to the first gear member is arranged to drive the second gear member in engagement with a rack to cause the second gear member to drive the transmission along the rack, and in a second condition, where no rack is present, with the brake means engaging an appropriate part of the epicyclic gear the wheels being driven from the pinion gear arrangement through the epicyclic gear.

Preferably the epicyclic gear may provide an increased drive ratio to the wheels over the second gear member.

Conveniently the ratio of the drive to the wheels is about three times the ratio of the drive to the second gear member.

Conveniently the epicyclic gear includes a sun gear integral with the axle, a carrier integral with the pinion gear arrangement, and an annulus gear on whose outside diameter the brake means operates.

Conveniently the pinion gear arrangement forms the carrier of the epicyclic gear by providing a plurality of idler shafts, disposed about a circle concentric about the axle and sun gear, to mount a plurality of planet gears.

The present invention will now be described by way of example only with reference to the single figure of the accompanying drawing which shows a cross section through a locomotive drive transmission according to the present invention. A hub 1 is rotatably mounted on an axle 2 via bearings 3 and 4.

The axle 2 carries a rail wheel at either end 5 and 6, so mounted that each wheel must rotate with the axle. The axle is mounted in a bogie or chassis of a locomotive (not shown) by axleboxes 7 and 10. Rail wheels 5 and 6 run on conventional rails 11 and 12.

The hub 1 has mounted thereon an input drive gear 13 and a pinion gear 14. One end of the hub 1 is adapted to provide a pair of more of idler shafts 15 and 16 on which are rotatably mounted a pair or more of planet gears 17 and 20. Between the planet gears 17 and 20, and enmeshed with them, is a sun gear 21 which is integral or effectively integral with the axle 2. An annulus gear 22 sits concentrically about the sun gear 21 and is meshed with the planet gears 17 and 20. A band brake 23 sits concentrically about the annulus gear 22. A rack 24 which may be single or multiple (eg. Abt) is fixed between the rails 11 and 12 and meshes with the pinion gear 14.

In operation the locomotive drive transmission is used as follows. On steep gradient rack section of the rail network drive from the locomotive engine is transmitted via input drive gear 13, hub 1 and pinion gear 14 and reacted against the static rack 24 between the rails 11 and 12. In this mode of operation the band brake 23, which is mounted on the chassis of the locomotive (not shown) is inoperative. This leaves annul us gear 22 free to rotate under the influence of the planet gears 17 and 20 and the sun gear 21. In this way the axle 2 and wheels 5 and 6 are free to rotate independantlyofthe hub 1 which is transmitting the drive. The drive from the locomotive engine to the pinion gear is arranged to give a high tractive effort at a low speed by use of an overall low ratio drive from engine to rack and pinion.

When the locomotive is used on shallow gradient sections of track, wheel adhesion is adequate to transmit the locomotive's drive. Rotation of the annulus gear 22 is prevented by operation of band brake 23 such that drive from the locomotive's engine is transmitted via input drive gear 13, hub 1, idler shafts 15 and 16, planet gears 17 and 20, sun gear 21 and axle 2 to the rail wheels 5 and 6. The annulus gear 22, planet gears 17 and 20, idler shafts 15 and 16 and sun gear 21 forming an epicyclic gear system which is arranged to provide a step up ratio of approximately 3 to 1 between the hub 1 and the axle 2. In this way on wheel adhesion sections of track, where the gradient is shallow, the locomotive may travel at about 3 times the steep gradient rack operated speed.

As can be seen from the above, the invention provides a very compact solution to the problem of driving a rack pinion gear at a different speed to the rail wheels, for different gradients, when the pinion gear and wheels are about a common axle. It is envisaged that this system will find widespread use in narrow gauge railways of the combined rack/ wheel adhesion type, especially in mining railway networks.

Claims

1. A locomotive drive transmission arrangement comprising an axle mounted between a pair of wheels having rotatably mounted thereon a pinion gear arrangement including:- a first gear member, a second gear spaced along the axle from the first gear member, and an epicyclic gear having associated therewith brake means, the arrangement being such that in a first condition with the brake means inoperative input to the first gear member is arranged to drive the second gear member in engagement with a rack to cause the second gear member to drive the transmission along the rack, and in a second condition, where no rack is present, with the brake means engaging an appropriate part of the epicyclic gear the wheels being driven from the pinion gear arrangement through the epicyclic gear.

2. A locomotive drive transmission according to claim 1, wherein the epicyclic gear provides an increased drive ratio to the wheels over the second gear member.

3. A locomotive drive transmission according to claim 2, wherein the ratio of drive to the wheels is three times the ratio of drive to the second gear member.

4. A locomotive drive transmission according to any of the preceding claims, wherein the epicyclic gear includes a sun gear integral or effectively integral with the axle, a carrier integral or effectively integral with the pinion gear arrangement and an annulus gear on whose outside diameter the brake means operates.

5. A locomotive drive transmission according to claim 4, wherein the pinion gear arrangement forms the carrier of the epicyclic gear by providing a plurality of idler shafts, disposed about a circle concentric with the axle and sun gear, to mount a plurality of planet gears.

6. A locomotive drive transmission substantially as hereinbefore described.