IM- PROVEMENTS IN TOWER' OR 'SLIP' BOLTS FOR FASTENING THE DOORS OF HOUSES, MAGAZINES, AND PORT-HOLES, AND OTHER ANALOGOUS PURPOSES
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by John Davidson at the Office of tho
Commissioners of Patents on the 7th January 1879.
JOHN DAVIDSON, of Glasgow, in the County of Lanark, North Britain. "IM-
PROVEMENTS IN TOWER' OR 'SLIP' BOLTS FOR FASTENING THE DOORS OF HOUSES,
MAGAZINES, AND PORT-HOLES, AND OTHER ANALOGOUS PURPOSES."
This Invention has reference to new or improved constructions or combinations
of the parts of tower bolts or slip bolts for securing the hinged or sliding doors of
houses and other places requiring to be closed in, such as the doors of powder or
other magazines, and the port-holes of ships, and other analogous purposes, and which
will make such bolts more easily and securely fastened than such bolts have been
as heretofore constructed. And the nature and novelty of the Invention consists
in making these bolts self-locking and retaining by certain now or improved
fittings for this purpose, which consist all as follows:-In forming the sliding bolt
proper truly cylindrical, with the long inner part working within the case con-
siderably smaller in diameter throughout than the fixing part which slides out
beyond the cose, and in mounting the said bolt to slide and swivel within a semi-
circular or U shaped parallel groove within the case, either projecting outwards
beyond the securing flange, formed at the upper open face of the groove, or made so
as to be sunk into a groove made in the wood or body of the door, with a lid or
face plate screwed on to the outside of the flange to cover in the groove and retain
or secure the bolt and its new and improved fittings all steady in working
position.
By these improvements a long spiral spring is mounted on the inner reduced
parallel part before mentioned of the bolt within the case, having its outer end
bearing up against the shoulder at the inner part of the enlarged outer securing.
bolt part, and secured thereto by an eye and screw pin or other equivalent, while
tho inner end of the spiral screw is similarly fixed to the inside of the plate cover,
or it might be other convenient part of the fixed case, and when desired made to
bear up against a pressure receiving or guiding snug at its back end, also preferably
secured to the inside of the cover plate in addition to the guiding snug at the back
part of the bolt, which retain it in true sliding and swivelling position. In the
inner plain part of the sliding bolt between the back end of the spring and the
back guide sufficient length is left for the actuating and retaining lateral pin, with
actuating finger knob outside screwed or otherwise secured into the bolt, and
which passes out through and slides in the short longitudinal groove formed for it

page_text: in the U case, with the usual two lateral retaining checks at the extreme ends of
the short groove for retaining the hand pin and bolt in their unlocked and locked
positions. This sliding groove and retaining checks are cut through the U shaped
case when this is made to project inwardly with the flange and lid screwed flat up
to the face of the door; but when this U shaped case is sank into the door, and the
flange screwed flush therewith, then the sliding groove and retaining checks are
cut through a sunk part or pocket formed on the flange cover plate, made deep
enough for the finger knob to lay in below the flush of the flange or door when in
its unlocked and locked positions.
The spiral spring is so fitted and secured on the inner part of its spindle (as
stated) as to act spirally and longitudinally, that is, to turn or press the lateral
finger pin always up towards that side on the sliding groove so as to swivel or
press it into the lateral retaining checks when brought opposite them, and also press
or push out the bolt longitudinally and lock it when the lateral finger knob is
turned out of its back and locked retaining check in a line with the short sliding
groove by the longitudinal force of the spring, which draws the finger pin opposite
the outer retaining check, which holds the bolt in its locked position, so that the
spiral or twisting action of the spring instantly and automatically turns and pushes
or draws the locking pin into this retaining check and holds it there in the locked
position until the finger pin is again forced out and brought back by hand against
the longitudinal power of the spring opposite the back retaining check, when the
said spiral action of the spring forces and turns the retaining finger pin into its
back retaining check, and so keep the bolt in this unlocked position until it is again
pressed or turned out of the check by hand against the spiral action of the spring
for locking the bolt by the longitudinal force of the spring, as before described.