This invention relates to railway bogies for carrying railway vehicles and more particularly to traction centres in railway bogies.

Traction centres transmit longitudinal traction and breaking forces between the railway vehicle body and the bogie and provide a pivot point to allow rotation of the bogie on curves and the vehicle body to move freely in the vertical and lateral directions.

Existing traction centres comprise a body mounted member which depends between, and is linked to, fore and aft bogie mounted members. The body mounted member may be linked to the bogie mounted member by a Watts linkage or by means of solid rubber elements having a stiffness equal to the load transmitted. Thus, there is always a stiffness present and, therefore, a permanent load path from the rail to the vehicle body. This has the effect of increasing the vibration of the vehicle body thereby greatly degrading the ride for passengers. In such systems it is essential that the traction centre be positioned at the pitch centre of the bogie to avoid the bogie pitch movements transmitting vibration to the vehicle body.

According to the present invention a traction centre for a railway bogie comprises a body mounted member depending between fore and aft bogie mounted abutment members whereby there is provided a gap between each abutment member and the body mounted member.

The bogie mounted abutment members are preferably made

of rubber and may be in the form of "stacks" (of rubber elements) which are secured (by bolting) to the bogie structure.

During normal running, i.e., when the vehicle is neither accelerating nor braking no longitudinal vibration will be transmitted to the body and the mass of the bogie will not couple with the natural body bending frequency. Also the height of the traction centre is no longer critical since the bogie pitch movements cannot transmit any vibration to the body. A further advantage of the invention is that the provision of the gaps allows the bogie to rotate when the vehicle is rounding a curve without being restricted by the abutment members.

During traction (acceleration) the aft gap will close and alternatively during braking the fore gap will close, increasing the longitudinal stiffness, however the stiffness is still lower than that experienced on many conventional systems and a high standard of ride is achieved, and the abutment members are capable of transmitting normal traction and braking forces.

In order to minimise any deterioration in the ride, due to the shear stiffness of the abutment member, each member may be faced with a low friction liner, to encourage the contact surfaces to slide before high forces can be generated. An independent longitudinal member may be provided alongside each abutment member to provide a stop to limit extreme movement of the bogie in relation to the vehicle body. A low longitudinal stiffness can be selected for the

rubber "stacks" since only normal loads need be transmitted by the rubber.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is a side elevation of a railway bogie incorporating a traction centre in accordance with the invention;

Figure 2 is an enlargement of the traction centre of Figure 1;

Figure 3 corresponds to Figure 2 but shows the traction centre during braking; and

Figure 4 corresponds to Figure 2 but shows the traction centre, during acceleration.

Figure 1 shows a traction centre 10 in a railway bogie 11 on a vehicle body 12. Referring specifically to Figure 2 the vehicle is in normal running and the traction centre 10 comprises a body mounted member 13 depending between fore and aft bogie mounted abutment members 14, 15 and a gap 16, 17 between each abutment member 14, 15 and the body mounted member 13. The bogie mounted abutment members 14, 15 are in the form of stacks of rubber elements 18 secured to the bogie structure 19 by bolts 20.

Independent longitudinal members 21 and 22 are provided alongside abutment members 14 and 15 respectively to provide a stop to limit extreme movement of the bogie in relation to the vehicle body.

A low friction liner 23 is provided in each abutment member 14, 15.

In Figure 3 the vehicle is braking or decelerating and the fore gap 16 has closed and the abutment member 14 is compressed.

In Figure 4 the vehicle is accelerating and the aft gap 17 has closed and the abutnment member 15 is compressed.