IMPROVEMENTS IN COMPENSATING PENDULUMS
Year: 1885

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I, THOMAS BUCKNEY, of N° 61 Strand, and N° 4 Royal Exchange, London in the
County of Middlesex, Clock and Watch maker do hereby declare the nature of my
invention for "IMPROVEMENTS IN COMPENSATING PENDULUMS and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement :—
My invention relates to compensating pendulums wherein a steel pendulum rod
is connected at its lower end to a tubular rod of zinc through which it passes,
while the upper end of the zinc tube is connected to the upper end of an outer
steel tube whose lower end is connected to the pendulum bob. My invention
relates to means for adjusting the compensation of such pendulums by varying the
point at which the upper end of the zinc tube is connected to the outer steel tube,
whereby the ratio between the operative length of the zinc tube and the combined
operative lengths of the steel rod and tube will be varied.
The construction which I employ for this purpose is shewn on the accompanying
drawings in which Fig. 1 shews an elevation of the pendulum, Fig. 2 a plan of the
same, Fig. 3 a vertical section, Fig. 4 a cross section through the pendulum bob;
Figs. 5 to 8 shew enlarged details.
A is the steel pendulum rod, connected at its upper end to the suspending spring
in the usual manner, and supporting on a screwed nut B on its lower end the zinc
tube C, whose upper end is connected to the outer steel tube D, to the lower end
of which is connected the pendulum bob X, by means of arms X at the middle of
its length. The mode of connecting the zinc tube C with the outer steel tube D
will be readily understood on reference to Figs. 5, 6, 7 and 8.
The zinc tube C has a screw thread cut some distance down from its upper end
upon its outer surface, and the steel tube D bas a corresponding screw thread cub
on its inner surface, and into these threads screws a cylindrical nut E E¹ having
corresponding screw threads on its inner and outer surfaces, thereby connecting the
two tubes together at a point which may be varied by screwing the nut up or down
between them, this being effected by means of the cylindrical extension E² with
milled flange E projecting up beyond the ends of the tubes. Thus as the length
of the zinc tube C is considerably less than that of the joint lengths of the steel
rod A and tube D it will be seen that in altering the operative length of the zinc
tube to the same extent as the operative length of the steel tube by shifting the
position of the nut E E', the compensation will be varied. In order to ensure that
the nut shall not shift its position when once it has been adjusted, I prefer to

page_text: construct it as follows. The parts E and E¹ on which the inner and outer threads
are formed, are made of two separate pieces, of which the inner part E shewn
detached at Figs. 7 and 8, has its extension E connected at its upper end by screws
or pins L to the extension E2 of the part E¹. Both parts are split part of the way
up at three or more points as shewn, and they have cylindrical holes Es formed,
half in the one part and half in the other, and into these holes fit rods F having
conically enlarged ends F¹, the lower ends of the holes in the nut being corre-
"spondingly enlarged, so that on drawing the rods upwards their heads F¹ will force
the part E inwards against the tube Cand the part El outwards against the tube D,
thus jamming the nut tight between the tubes, while on lowering the rods again,
the parts of the nut will spring back sufficiently to render it free to be adjusted.
The rods F are for this purpose connected by their upper ends to a ring G that
is held loosely in a cap H screwed on to the upper end of the cylinder E³, so that
on screwing the cap upwards or downwards the nut is tightened or loosened as
above described. The tube C is provided with two pins II projecting through
holes in the tube D by which it can be held so as to prevent it from turning when
the nut E E¹ is being adjusted. In place of the rods F with coned heads any
suitable equivalent means may be employed for effecting the required wedging
action upon the nut. Holes are formed at K in both the tubes C and D in order
to allow free access of the air to all three parts A, C and D, in order that they may
be equally affected by change of temperature.
It will be evident that the above described arrangement for fixing a screwed nut
between two tubes or between a rod and a tube may also be used for other purposes
than for compensating pendulums.
Although of the foregoing I have spoken of the rod and tubes of the pendulum
as being of steel and zinc it is to be understood that my invention is equally
applicable in cases where other metals than steel and zinc are employed.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The method of adjusting the compensation of pendulums by varying the
point of connection between the two tubes of different metal, substantially as
herein described.
2. The use for adjusting the compensation of pendulums, of a cylindrical nut
with inner and outer screw threads screwing into an outer and inner thread
formed respectively on the concentric tubes of different metals, substantially as
herein described.
3. The herein described construction of cylindrical nut consisting of two
separate parts E and E¹ having longitudinal slits, and which are forced respec-
tively inwards and outwards by rods F with coned heads, or equivalent device
having a wedging action in order to jam the nut in position between the concentric
tubes into the space between which it is screwed.