IMPROVEMENTS IN APPARATUS APPLICABLE TO WIRE AND SIMILAR CONNECTIONS FOR WORKING RAILWAY SIGNALS AND THE LIKE, WHEN CONNECTIONS ARE LIABLE TO VARIATIONS IN LENGTH 33 SUCH
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by William Robertson and Edward
Phillips Holtham at the Office of the Commissioners of Patents on the
22nd January 1883.
WILLIAM ROBERTSON, of 45, Calthorpe Street, in the County of Middlesex,
and EDWARD PHILLIPS HOLTHAM, of 8 Crossley Street, in the County of Middlesex,
Engineers, "IMPROVEMENTS IN APPARATUS APPLICABLE TO WIRE AND SIMILAR
CONNECTIONS FOR WORKING RAILWAY SIGNALS AND THE LIKE, WHEN
CONNECTIONS ARE LIABLE TO VARIATIONS IN LENGTH
33
SUCH
It is frequently the practise on railways to place signals at considerable distances
from the signal cabins whence they are operated and to communicate motion to
the former by means of wires, chains or connections of a similar character. These
connections, owing to the strain they are subjected to and to changes of temperature,
are liable to variations in length; which, if not compensated for, lead to inaccurate
working of the signals and consequently to improper signals being exhibited.
With a view to provide against this defect and risk, we insert in the wire or
other connection between the two points alluded to an apparatus which ensures
the full stroke being given to the semaphore or other signal upon the hand-lever
being vibrated or moved through its full stroke, irrespectively of whether the wire
or other connection happens to be taut or slack.
The apparatus referred to consists of a grooved wheel or drum over which a
chain or other flexible portion of the connecting wire passes; the said drum being
by preference counterweighted to act against the pull of the connecting wire.
Mounted on a pivot in or near the periphery of the drum, and extending in the
radial plane thereof, is a link, the opposite end of which is attached to the free
end of a radius bar, or is otherwise suitably guided. The link carries at or about
the middle of its length a roller which travels in a slot formed in or attached to
a sliding bar conveying motion to the signal; the slot being so disposed in relation
to the line of motion traced by the roller on the link that the slotted bar is cause I
to reciprocate a sufficient distance to impart the full motion required for the signal,
whilst the roller on the link travels to or towards one end of the slot in the said
sliding bar. This result is attained on the drum having been rotated a quarter
Prine 211

page_text: revolution or thereabouts; but if the pull on the connection be still maintained
and the drum be further rotated, the roller on the link commences to travel
towards the opposite end of the slot in the sliding bar. During this latter
operation, however, the sliding bar, owing to the shape and position of its slot, is
retained in the position to which it had already been moved during that portion of
the motion of the link first described. On the strain on the connecting wire
being released, the drum returns to its original position, a counterweight being
commonly employed to effect this motion. The link, being connected to the drum
periphery as aforesaid, hereupon slides the slotted bar in the opposite direction and
causes the semaphore or other signal to resume its normal attitude.
It will thus be perceived that if the connecting wire happen to be slack, the
motion of the hand-lever in the signal cabin is primarily effective for taking up
that slack, and secondarily for actuating the apparatus in the manner described.
On the other hand, if the connecting wire be taut, the first portion of the motion
of the hand-lever actuates the apparatus, whilst a continuation of the operation
can neither derange the apparatus nor unduly strain or stretch the connecting
wire.
Although we have described our improved apparatus as adapted to wire or
similar connections for actuating railway signals, it will be obvious that the
apparatus is applicable under any circumstances where similar objects have to be
attained.