GB1580033A - Bogies for railway vehicles - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO BOGIES FOR RAILWAY VEHICLES (71) I, ARCHIBALD WATSON KIDD, a British Subject, of Seend Close, Seend, Melksham, Wiltshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to bogies for railway vehicles.

It is well known that when railway vehicles travel, particularly at speed, on railway tracks, unwanted hunting movements commence so that the vehicle no longer proceeds down the track in straight line motion but becomes subject to a complicated motion consisting of a mixture of sinusoidal lateral hunting, yawing, fore and aft and other unwanted oscillations in varying mixture.

This simple fact is one of the reasons why so far really high speed say 150 mph, railway travel has not become common throughout the world.

These hunting movements are caused by the fact that existing rolling stock has the wheels in twin sets connected by means of a rigidly attached axle. The idea therefore of a railway wheel at present is a contradiction of the facts - railway wheels exist in pairs in conjunction with an axle and not as separate identities.

Assuming that the wheels have perfectly cylindrical treads and are of exactly the same diameter it could be argued that such a wheel-set will travel straight down the track but in fact it is in a state of unstable equilibrium and any slight disturbing force will cause it to yaw from side to side and an irrational form of hunting will set in, particularly at speed. Similarly wheels with coned or specially profiled treads will hunt with greater or less frequency and complexity. These problems may be alleviated in a number of ways, such as by the use of dampers to quench the hunting movements, but the basic tendency to hunt will still be there. Even independent wheels, if used, could not be guaranteed not to hunt unless at the same time there was something special about the way they are mounted and also something special about their tread profile.

According to this invention I provide a four-wheeled bogie for a railway vehicle in which each wheel of each pair of opposite wheels is mounted independently of the other while being held at the correct gauge apart and each wheel has a peripheral profile so formed that there is a tread region adjacent the flange having a diameter increasing towards the flange at a rate greater than any increase (if any) in the diameter of the rest of the tread.

In carrying this invention into practice I propose to mount each pair of wheels on one side of the bogie in a frame. Each frame is free to pivot at its centre both vertically and laterally to allow for irregularities in the track and for cornering respectively as well as to permit vertical movement for suspension reasons. At the same time each of the two side frames is rigidly, though pivotally, cross-connected to the centre of the other one by a rigid transverse beam or frame so that the centre of the two side frames are firmly maintained at the correct lateral spacing.

To assist in keeping the side frames at the correct lateral spacing and to prevent any tendency for shimmy or vibration within the frames, I propose to connect the outward ends of each side frame by means of a kind of track rod, provision being made for flexibility to accommodate turning and suspension rise and fall.

In order to make the assembly selfcentering I propose a special wheel profile in which the majority of our profile is cylindrical starting at the outer edge away from the flange. At some point towards the centre line of the tread the profile however alters, pref erably in the shape of an exponential curve merging away into the near-vertical side wall of the inner edge of the flange. Alternative shapes are doubtless possible, such as one or more coned angles.

The action is as follows. When travelling straight down the centre of the track all four wheels of a bogie are running on the cylindrical part of their treads. Assume now that some disturbance causes the bogie to move slightly to one side. It will be seen that two correcting forces being to operate - firstly since the wheels on the side to which the bogie has gone will now be riding slightly up on the curved part of the wheel tread, they will marginally be raised higher than they were when on the cylindrical part. On the other hand the wheels on the opposite side will still remain on the cylindrical part of the tread and will not have suffered any change in elevation. The force of gravity will therefore tend to put down the side that has been raised and this can only be effected by moving the bogie back to the centre.

Secondly, and without doubt much more powerfully, the reaction of the line of contact between the first pair of wheels mentioned above and the rail will now have a considerable inward component and this will effect an immediate and automatic correcting and centering effect.

Several forms of construction are possible and the optimum will undoubtedly be the one which has maximum rigidity combined with minimum unsprung weight.

Several forms of the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a part-sectional side elevation of a bogie assembly according to the invention, Figure 2 is a plan view of the assembly shown in Figure 1, Figure 3 is a part sectional side elevation of a second form of bogie assembly according to the invention, Figures 4 and 5 are part-sectional views in plan and end elevation respectively, of the assembly in Figure 3, Fig. 6 shows part sections of four alternative forms of wheel tyre profiles, and Fig. 7 is a part-sectional side elevation of a third form of bogie assembly.

Referring to the drawings and more particularly to Figs. 1 and 2, the wheels 2 of the four-wheeled assembly are mounted as two independent tandem pairs in respective side frames 4 (only one of which is shown), each wheel having a stub axle 6 journalled in roller bearings 8. Each frame is of rigid construction and. as shown. is fabricated from steel plate with a central stiffening rib 10. At the middle part of the frames. each is pivoted to a large diameter gudgeon pin 11 which connects the frames to pistons 13 of vertically resilient means.

In each, the piston 13 can slide vertically in a cylinder 12 which is an integral part of attaching bracket 14. The piston has a hollow body within which are contained spring elements 16. At the top of the cylinder, a dummy head 22 depends to provide a seating face for the stack of spring elements, and forms an annular space 24 between the head and the outer wall of the cylinder receiving the end of the piston thus ensuring that the upper elements do not foul the edge of the piston. Since relative rotation between the piston and the cylinder is possible, the frame can turn about the axis of the parts, for example, when running over a curved track.

The attaching brackets 14 secure the two halves of the wheel assembly to the vehicle and, they are bolted together at their inner ends 26. By insertion o.f packing between their adjacent faces the gauge of the assembly can be adjusted, the holes 28 for securing bolts to the vehicle being of elongate form.

Alternatively strong but lockable sliding means of altering the length of the cross beam and therefore the gauge may be provided. Similar provision must be made on the tie rods.

It will be appreciated that, as described so far, the assembly is so constructed as to ensure that each of the side frames 4 is constrained to travel in a vertical plane, and the centre points of the two frames are maintained at gauge distance. Thus, the leading wheel of one frame cannot wander inwards off its rail without forcing the flange of the trailing wheel up and over that rail. Tie rods 30 are provided attached at opposed ends of the two frames through substantial rubber bushcs 32 thus permitting freedom from independent vertical movement of their attaching points.

An altcrnative construction according to the invention is illustrated in Figs. 3 to 5 of the drawings, parts similar to those already described being indicated by the same reference numerals. Thus, as in the previous example, each side frame 4 is independently attached through a large diameter gudgeon pin 11 to the piston 13 which is vertically movable in its cylinder 12 against the force of spring elements (not shown).

An annular recess 50 in the cylinder wall provides a location for a friction band (not shown) bearing on the piston 13. The band may comprise an inner resilient lining backed by a split metal ring. the latter being secured against rotation in the annular recess and arranged to be forced inwards by a series of radial plungers operating through holes of the outer side wall of the recess. These plungers project somewhat externally and bear against an external metal tension ring which can be tightened by a turn buckle to adjust the force it exerts. This forms a means of adjusting as desired the damping of the vertical and also the turning movements of the piston in the cylinder.

The cylinder in this example is not rigidly attached to the frame of the vehicle but is separated from opposed mounting members 52, secured to the vehicle body, by a pair of rubber pads 54 having their bearing surfaces, as shown in Fig. 3, inclined inwardly and upwardly, in the longitudinal plane, towards each other. To limit the amount of movement of the cylinders in the transverse direction, resilient stops 56 are provided, with a clearance between side flanges 58,60 of the mounting member and its cylinder respectively.

The braking system comprises a single brake shoe 34 for each wheel. Lugs 62,64 on the side frame 4 provide pivots 66,68 for an operating lever 70 and a follower link 72 respectively, the lever 70 being connected to the brake shoe through an intermediate link 74 and the follower link being pivoted directly to the shoe. A fluid ram 76 connected between the levers 70 (only one of which is shown) on opposite sides of the pivot 11, when extended, applies the brakes to the two wheels journalled on the frame. This action is resisted by compression springs 78 (only one of which is shown) interposed between each lever 70 and the frame. When the fluid pressure is released from the ram, each spring acts to lift its brake shoe from the wheel.The connection of each spring to the frame includes a push rod 80 secured by locknuts 82, by which means its effective length can be adjusted to regulate the force of the spring 78.

As in the first-described embodiment, tie rods (not shown) interconnect the ends of the two frames of a bogie assembly through rubber bushes 32, while the two cylinders each have integral extensions 84 which can be bolted together and between the engaging faces of which packing can be inserted to adjust the gauge of the assembly.

In the invention so far described the bogie lacks means of self centering itself on the rails so that for instance the flange of the front wheel of a tandem pair may chronically bear on the side of the rail leaving of course the rear wheel with its flange as far away from the rail as permitted by the gauge clearance.

In order to ensure that the wheels run centrally on the rail and in fact to provide then with a positive urge to do so, each wheel tread in one form of the invention is cylindrical or nearly cylindrical over say the outer half of its axial width but increases in diameter over the inner half in the form of an exponential curve defining an intermediate region until the tread merges with the flange.

Since the opposite wheels are not connected by an axle as is the case with ordinary rolling stock there is no tendency for one wheel momentarily running on a different diameter from the other in the opposite pair to interfere in any way with the said other wheel.

Therefore if there is lateral displacement of a pair of opposite wheels one will ride up onto a larger diameter thus slightly raising that side of the bogie against gravity but the other wheel will stay at the same altitude as it was initially since it will be running on the cylindrical portion of its tread. The force of gravity will act as a correcting factor as in returning the raised wheel to its original altitude it will bring back this wheel to its original lateral position also.

Furthermore, since the rail in practice has a curved inner top edge, and bearing in mind that the reaction of the rail on the wheel when the latter is running on the inner curved portion, will be approximately perpendicular to the line of contact, it will be seen that the rail reaction also acts as a centralising force.

Four examples of wheel profiles according to the invention are shown in Fig. 6. The preferred form described above is shown in Fig. 6(a). There is a cylindrical region 90a between which and the flange 92 is an intermediate region 94a the profile of which takes the form of an exponential curve. As shown in Fig. 6(b), tread region 90b is coned at a lesser angle than intermediate coned region 94b but it is desirable, to moderate any tendency to hunting about the longitudinal axis of a vehicle, to keep the angle of conicity of the tread region relatively small. The third example, in fig. 6(c) has a cylindrical tread region 90c which blends into a curved intermediate region 94c. In Fig. 6(d) there is a cylindrical tread region 90d and a coned region 94d; a similar effect could be achieved by using a continuous, e.g. parabolic, curve for the profile of these two regions.

Generally speaking, the width of a wheel tyre from its flange is about twice the width of the rail on which it runs. In this case, the tread region should occupy at least one third of said tyre width and preferably more than one half of said width.

Referring to Fig. 7 this is another modification. Instead of the rigid beam 4 running fore and aft from the front wheel to the back wheel, two halves 96 of the frame are made separately and both pivoted to the pin 11 to allow vertical movement of each wheel 2 but without allowing any lateral shimmy or wander. In this construction a stack of leaf springs 100 is provided between the gudgeon pin 11 and the piston 13. The leaf springs 100 are rigidly held in the construction illustrated but they can be pivoted at the centre or arranged to roll on a convex surface. Alternatively the leaf springs could be replaced by coil springs.

Another constructional difference from what is shown in Fig. 3 is in the mounting of the cylinder 12. In Fig. 7 the mounting mem bers 52 instead of being inclined outwardly and downwardly are mounted so as to extend inwardly and downwardly from the vehicle frame.

WHAT I CLAIM IS: 1. A four-wheeled bogie for a railway vehicle in which each wheel of each pair of opposite wheels is mounted independently of the other while being held at the correct gauge apart and each wheel has a peripheral profile so formed that there is a tread region adjacent the flange having a diameter increasing towards the flange at a rate greater than any increase (if any) in the diameter of the rest of the tread.

2. A four-wheeled bogie according to Claim 1 in which each fore and aft wheel on each side of the bogie is arranged in a side frame, the two side frames being pivotally connected at their centres to a cross member to allow turning without tilting or gauge variation.

3. A four-wheeled bogie according to Claim 2 in which each side frame is formed in two halves each half being separately pivoted in a vertical plane.

4. A four-wheeled bogie according to Claim 2 or 3 wherein each side frame is separately connected to the vehicle through resilient means.

5. A four-wheeled bogie according to Claim 2 or Claim 3 wherein each side frame is connected to the other by tie rods near their extremities.

6. A four-wheeled bogie according to any one of the preceding claims wherein the said intermediate region is an exponential curve.

7. A four-wheeled bogie for a railway vehicle substantially as described with reference to Figs. 1 and 2, Figs. 3 to 5 or Fig. 7 of the accompanying drawings.

8. A railway vehicle having a fourwheeled bogie according to any one of

Claims (1)

1. Claims 1 to 7.