To obviate the inconvenience frequently resulting by the sleepers or blocks sinking in the soil or losing their perpendicularity; and hence of destroying the level or parallelism of the rails, Mr. Jessop patented in 1833 a method of framing the chair distinct from the pedestal; the latter being fixed firmly to the sleeper, and the chair being united to the pedestal by a universal joint or hinge. This arrangement permits the pedestal to adapt itself to any irregular sinking of the block or sleeper on which it rests, and insures a firm and solid bearing upon its base. The patentee also effects it by the combined motion of a hinge joint, or other means permitting motion between the pedestal and the chair, and a moveable joint formed at the junction of the chair and rail, so as to produce the same effect. The following drawings represent several methods of constructing the universal joint, in all of which rr are the rails, c c the chairs, pp the pedestals, and b b the blocks or sleepers; jj are the junction bars of cast or wrought iron, by which the opposite chairs are connected together, and the rails are thereby held parallel to each other, and at a proper distance apart, and are also retained in a suitable position to insure a flat bearing on the surfaces of the rails for the wheels to travel upon; s s are cast-iron bed-plates or sleepers, (which may be used to support the rails where stone is expensive,) so constructed that the pedestal may be readily adjusted, by the introduction of a wedge or packing, to a proper level, without disturbing the seats which the bed-plates may have acquired on the ground; the same method of construction being applicable to the pedestals, when they are attached to stone blocks.
Fig. 1 is a side view of its adaptation to the ordinary railway in use in the north, at the period of the invention.
Fig. 2 shows the plan; and Fig. 3, the cross section. Two of the stone blocks b are drawn in an inclined position to show the action of the pedestal.
Figs. 4 and 5 are sections of the pedestal and chair, showing an orbicular universal joint, by means of which the pedestal adapts itself to any irregular sinking of the stone block or other sleeper, whilst the connecting or junction bars retain the rails in their proper gauge, and their opposite surfaces in the same plane or straight line.
Figs. 6, 7 and 8, are other views of the pedestal and chair.
Figs. 9, 10 and 11, are a side view, plan, and section of a cast-iron bed-plate, used as a substitute for the stone blocks; showing also the method of adjusting the rails by means of wedges or packings introduced between the bed-plates and the base of the pedestal, which is made to fit in the recess formed in the bed-plate, and secured laterally by means of a wedge or key. The patentee states his claim to consist in "constructing railways, to the using of chairs and pedestals, which are capable of turning or moving on universal or other similar joints, as above described, whereby the railway will not be so liable as heretofore to be deranged by the sinking of the blocks or sleepers, whether of stone, wood, iron, or other material."