Bogies for railway vehicles are known, particularly in electric and diesel electric locomotives, which have a motor pivoted on the driving axle of the locomotive, with the motor shaft parallel to that axle. A gear on the motor shaft is permanently meshed with a gear on the driving axle.

Such an arrangement is widely used but it suffers from the disadvantages that, even with well-designed motor suspension, irregularities in the track upon which the locomotive is run may produce a vertical acceleration of the motor and its fixings.

As such an arrangement has a large unsprung weight, the forces resulting from this acceleration of the mass of the motor and fixings are large and can increase the likelihood of the development of cracks in the rail and/or the fatigue and failure of the motor fixings.

In a second known arrangement, a driving gear is suspended elastically on the drive axle using two pairs of plates slidably engaged with one another in tongue and groove arrangements. The pairs of plates are arranged such that one pair allows horizontal movement of the gear and the other pair allows vertical movement of the gear.

This system was used in Fowler road locomotives, No. 6202 Turbo motive (the LMS turbine driven engine) and it is used in many modern electric locomotives.

However, the system is heavy when designed to withstand large torque and high horsepower. Lubrication and maintenance are problematic, and the large mass of the system is mainly unsprung causing problems as in the first described arrangement.

Another known arrangement, which has been used in steam, electric and diesel mechanical locomotives, comprises a jackshaft in bearings fixed to the bogie frame, and coupling rods connecting cranks on the jackshaft to cranks on the axles.

The jackshaft is at the same centre-line height as the axles on uniform, level tracks but the axles are allowed to rise and fall vertically over irregularities in the track as necessary.

The rising and falling of the axles relative to the jackshaft leads to a change in the distance between the crank on the jackshaft and the cranks on the axles. Due to the fixed length of the coupling rods, it is necessary to introduce flexibility in to the system, for example by using bearings with larger clearances. However, such bearings can require unacceptably high levels of maintenance and can be prone to failure.

In a fourth known system, using a cardan shaft drive, the gear box must turn the rotating motion through a right angle. In a double bogie locomotive this results in a requirement for two main engines, one driving in each direction, usually through a hydraulic clutch/torque converter, as was seen typically in the western region diesel hydraulic locomotives.

The cardan shaft drive system has a large unsprung mass resulting in the problems outlined above. The transmission of torque from one axle to another is also problematic; this is sometimes done through idler gears between axles, but track irregularities lead to fatigue fractures at the roots of the gear teeth even at low horsepower.

It is an aim of the present invention to provide a bogie which has a relatively small unsprung mass, which is simple and robust and which overcomes or alleviates some or all of the problems associated with known bogies and power transmission systems.

In accordance with the present invention, there is provided a drive and axle assembly for a railway vehicle, the assembly comprising two side frames parallel to one another; a first axle mounted horizontally between the side frames in a manner allowing movement of the first axle relative to the side frames in a fore-and-aft direction and in a vertical direction, ends of the first axle having respective flycranks; a crankshaft mounted horizontally and substantially parallel to the first axle between the two side frames, ends of the crankshaft having respective cranks each arranged in an in-phase relationship with the respective flycrank of the adjacent end of the first axle ; coupling rods fixed to the respective crankshaft cranks and the adjacent respective first axle flycranks such that rotation of the crankshaft causes rotation of the first axle; and at least one tie rod coupling the first axle and the crankshaft such that the lateral distance between the crankshaft and the first axle remains constant.

Such an assembly benefits from a small unsprung mass compared, for example, with a nose hung traction motor assembly. Compared with the traditional jackshaft and coupling rod assembly, it also benefits from the advantage that the distance between the axle and the crankshaft is kept constant, negating the requirement for flexibility in the length of the coupling rods and/or for the use of bearings with large clearances. It is therefore robust and requires comparatively low maintenance.

Preferably, the assembly may further comprise at least one further axle which is preferably also coupled to the crankshaft.

Advantageously, at least one of the axles is mounted in a manner allowing lateral movement. This lateral movement, parallel to the longitudinal axis of the axle, assists the railway vehicle in cornering.

The railway vehicle may advantageously be a bogie for a locomotive, perhaps of centreless design. However, the vehicle may instead be a rigid locomotive, perhaps having leading and/or trailing pony trucks.

Specific examples of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:- Fig. 1 is a simplified elevation of parts of a bogie in accordance with the present invention; Fig. 2 is a diagrammatic perspective representation of a bogie in accordance with the invention; and Fig. 3 is a plan view of the coupling of an axle to a crankshaft in accordance with the invention.

A bogie of the present invention is represented Figs. 1 and 2. Axles 2a, 2b and 2c and crankshaft 4 extend horizontally between side frames 5. The axles 2a, 2b and 2c and the crankshaft 4 are coplanar, and the crankshaft 4 is disposed equidistant from the first axle 2a and the second axle 2b.

The axles 2a, 2b and 2c and the crankshaft 4 are each provided with flycranks 6a, 6b, 6c and 6d respectively, in phase with one another. Similar flycranks are provided at the other ends of the axles and the crankshaft, out of phase by 90 ° with the flycranks shown in Fig. 1.

The axles 2a, 2b and 2c are each mounted in a manner allowing vertical movement of the axles and fore-and-aft movement (left and right in the drawing), in a known manner. The third axle 2c may also be mounted in a manner allowing it to move axially. This feature is also well-known and has been used, for example, in the Schwartzkopff-Eckardt bissel-bogie used from 1935 in Germany, the SNCF 240 P class locomotive bogie and in rigid locomotives such as the 0-10-0 tank locomotives of the Midi railway and the last series of 4-8-4 locomotives of the Union Pacific class. However, this feature is not present in the illustrated embodiment.

The coupling of the first axle 2a to the crankshaft 4 is illustrated in detail in Fig. 3. The coupling of the second and third axles is shown in Figs. 1 and 2.

The first axle 2a is coupled to the crankshaft 4 by a first coupling rod 8a having a crankshaft-end eye 14 and an axle-end eye 16 through which it is coupled to the crankshaft crank 6d and the first axle flycrank 6a respectively. The second axle 2b is similarly coupled to the crankshaft 4 by a second coupling rod 8b having a crankshaft-end eye 18 and an axle-end eye 20.

The third axle 2c is coupled to the second axle 2b by a third coupling rod 8c having a crankshaft-end eye 22 and an axle-end eye 24. The third coupling rod 8c extends between the third axle flycrank 6c and an eye 11 of a coupling radius rod 10 rigidly connected to or integrally formed with the second axle end of the second coupling rod 8b.

In the embodiment shown, a first tie rod 12a extends between the first axle 2a to which it is coupled through an eye 26 and the crankshaft 4 to which it is coupled through a crankshaft-end eye 28, constraining the first axle 2a to move in an * arc of a circle about the axis of the crankshaft 4. The second axle 2b is similarly constrained by a second tie rod 12b extending between the crankshaft 4 and the second axle 2b.

The eye-to-eye length of the first and second coupling rods 8a, 8b is the same as the eye-to-eye length of the first and second tie bars 12a, 12b respectively so that the first axle crank 6a, the first coupling rod 8a, the crankshaft crank 6d and the first tie bar 12a form a first parallelogram, and the crankshaft crank 6d, the second coupling rod 8b, the second axle crank 6b and the second tie rod 12b form a second parallelogram.

It will be seen that the first and second axles 2a, 2b are constrained to fore- and-aft and vertical movement in arcs of respective circles about the axis of the crankshaft 4 having radii equal to the eye-to-eye lengths of the first and second tie rods 12a, 12b respectively. Since these radii are also, respectively, the eye-to-eye lengths of the first and second coupling rods 8a, 8b, no flexibility is required either in the lengths of the first and second coupling rods Sa, 8b or in the clearances of the coupling rod bearings.

In a similar manner, the third axle is constrained to fore-and-aft and vertical movement in an arc of a circle about the centre of an eye 30 of a tie radius rod 32, the circle having a radius equal to the eye-to-eye length of the third tie rod, which radius is equal to the eye-to-eye length of the third coupling rod 8c.

The crankshaft-end-eyes of the first and second tie rods 12a, 12b are rotatably mounted on the crankshaft using plain bearings. The first and second coupling rods 8a, 8b coupled to the crankshaft crank 6d use non-self aligning roller bearings and to the first and second axle cranks 6a, 6b use self-aligning roller bearings The axle boxes, comprising the axle-end eyes of the tie rods, comprise self-aligning roller bearings.

The lateral movement of the axle boxes is constrained by a respective shim 34 slidably held against the bogie frame by a respective bracket 36. The shims 34 slide in vertical and fore-and-aft directions between pads of low friction material, e. g.

Railco dry friction material which does not require lubrication.

In embodiments where lateral movement of the third axle 2c is required, the axle box of that axle would not be so constrained and the respective joints between the third coupling rod 8c and the coupling radius rod 10 and between the third tie rod 12c and the tie radius rod 32 must be spherical joints of a known type, e. g. as used in the GWR 6000 class and in the NER 901 class.

In the embodiment described, the coupling rods are coupled to fly cranks on the axles as in known narrow gauge locomotives. However, the coupling rods may also be coupled directly to the wheel bosses as is also known.

Furthermore, arrangements in accordance with the invention may comprise, one, two, three, four or more driven axles.