IMPROVEMENTS IN THE CONNECTING PARTS OF MACHINERY AND STRUCTURES LIABLE TO IMPULSIVE FORCES
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by Frederick Arthur Paget at the
Office of the Commissioners of Patents, with bis Petition, on the 11th
September 1866.
I, FREDERICK ARTHUR PAGET, of 1, Seymour Chambers, York Buildings,
Adelphi, in the County of Middlesex, Civil Engineer, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN THE CONNECTING PARTS OF
MACHINERY AND STRUCTURES LIABLE TO IMPULSIVE FORCES," to be as follows:-
The connecting parts, such as bolts and rivets of machinery and structures,
when subjected to impulsive forces are peculiarly liable to fracture. Now I
obviato this danger by causing the given impulsive force to act through a
certain distance, which I effect by so proportioning the connecting part or
parts, and (or) by so adapting certain contrivances described in the Letters
Patent granted to me on the 29th May, A.D. 1865, that such connecting
part or parts can stretch and (or) yield in the direction of the impulsive strain
or strains; by this greater extension, according to known principles, less
substance is required in the given connecting part to resist distortion and
rupture. The way in which an ordinary screwed bolt is proportioned renders
it peculiarly liable to snap at its screwed end under the action of an impulsive
force acting parallel to the longitudinal axis. Even under a gradually applied
load a bolt necessarily gives way at its threaded portion, as the cross sectional
area at the bottom of the threads is less than that of the shank; and under
an impulsive load, the stretch being almost entirely confined to these reduced
parts (as the shank is kept from extending by its larger cross sectional area),

page_text: the bolt generally snaps at some part of the thread below the nut. One means
whereby obviate this is by making the cross sectional area of the shank of
the bolt equal to that of the threaded portion; which I effect by forming the
shank hollow, and making the threaded part and the head solid. I know
that bolts have been formed both solid and also hollow throughout, but I am
not aware that bolts have been constructed with hollow shanks and solid
threaded ends combined. Besides the advantage thus gained, which is due
to the equal proportioning of the parts, I find that metal when disposed in the
form of a tube affords more power of elongation under tension than when
such metal is gathered together into the solid form; such bolts with tubular
shanks I generally prefer to make of steel, more especially when used for
armour plates, the connecting parts of which description of structure require
great powers of extension. When the shot strikes the plate, the latter
necessarily gives way at the spot struck to an extent varying with many
circumstances, amongst which is the stiffness of the backing. The portions of
the plate round about the part struck by the shot react forwards in a contrary
direction, and thus the conical head of the bolt being firmly held in the
armour plate bring a powerful impulsive force to bear on the threaded portions
of the bolts attached by a nut or nuts to the skin of the ship. When the
shot penetrates the armour plate and backing, and drives forward the skin of
the ship, this action on the bolts is greatly intensified; a maximum amount
of elasticity beyond the limits of the working load being thus required in all
the connecting parts of armour plating. I apply in addition to the use of
bolts of steel with hollow shanks underneath the nuts of the large bolts, and
underneath both the heads and nuts of the smaller bolts used to connect the
backing, and in certain descriptions of armour plating the inside skin to the
skin of the ship, and further underneath one of the heads of the rivets used
to connect the plates, one or more of the steel cup washers for which Letters
Patent were granted to me on the 29th May, A.D. 1865. I find that these
appliances not merely lock the nut of the bolt on which they are placed and
equalize the strain on the threads, but also completely protect the connecting
I further
parts of machinery and structures liable to impulsive forces.
find that as in the construction of armour plating I cannot always make my
steel cup washer of a sufficiently large size it is necessary to use two or more
of a smaller diameter; a pair of these I arrange by placing them with their
broadest bases facing and touching each other; these washers I sometimes
make of iron, though I prefer the use of steel; and I sometimes split them
up radially, though I generally prefer to make them solid. Amongst other
kinds of machinery and structures liable to impulsive forces, to the connecting

page_text: parts of which I apply my steel cup washers, are the so-called cheese couplings
of screw shafts, as also to the holding-down bolts of the bearings of such
shafts. I place a steel cup washer' severally underneath the head and under-
neath the nut of the bolts used in connecting these cheese couplings together;
and by this means I prevent the injurious effects on the connecting parts and
elsewhere often caused by the ship heaving in a heavy seaway, or the similar
effects often produced when such a vessel is docked for repairs. The connecting
parts of steam hammers are similarly liable to injury by the impulsive forces
brought into action against them at each blow, and to such parts I find that my
steel cup washers are very useful. When a steam thrasher is fed unequally
during its rapid motion the bearings require a temporary adjustment, which is
provided by the employment on the holding-down bolts of one or more steel
cup washers. During the passage of the trains the bolts used for the fish
joints of permanent way are greatly liable to elongation and distortion by the
impulsive forces brought into play, and these actions I avoid by employing
one or more of my steel cup washers under each of the bolts holding the fish
joint together, and I sometimes place a steel cup washer both underneath the
head and underneath the nut of each of these bolts.