Year: 1886

page_text: I, CHARLES DAVY of 24 Lawson Road Sheffield in the County of York,
Engineer, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
The object of this Invention is to substitute a silent motion for the pawl and
ratchet wheel used in ratchet braces whereby a noiseless action and an instan-
taneous grip are obtained and lost motion avoided.
The Invention consists of a friction clutch interposed between the handle and
spindle and formed by an externally coned nut screwing on a thread of rapid pitch
cut upon the tool spindle and fitting in a correspondingly coned eye on the handle,
the eye being confined between fixed collars and a spring forcing the coned surface
of the nut constantly into frictional contact with that of the eye, so that on the
working stroke of the handle the nut will turn with the handle and become
jammed, and on the return stroke the eye will turn on the nut.
Reference is to be had to the accompanying drawing forming part of this Speci-
fication which represents the improved tool in longitudinal section, the spindle
being in elevation.
A is a coarse screw thread of rapid pitch cut upon a suitable part of the spindle
between the usual drill socket a at one end, and the usual feed screw thread a¹
at the other end. B is a nut threaded internally to fit A and turned of conical
form externally. C is the eye of the handle bored conical internally to correspond
to and fit accurately on B. The eye C is closely confined between collars D D¹ on
the spindle whereby the handle is maintained at right angles to the spindle. These
collars may be held in place, the one by a shoulder turned on the spindle and the
other by screwing on a threaded part c of the spindle, or they may be otherwise
fixed. The length of the nut B is slightly less than the depth of the eye, as
shewn, and between the larger end of the nut and the adjacent collar (D for
example) is interposed a coiled spring E which is partly received in an annular
groove turned in the face of said collar and in the larger base of the nut, as shewn.
In the example shewn the upper end of the nut is of the largest diameter, the
apex of the cone being towards the drill and the screw A is in the same direction
as the feed-screw a¹. Were the direction of the cone reversed with regard to the
drill the screw A would necessarily be of contrary direction.

page_text: The pitch of the screw A the angle and mean diameter of the coned surfaces are
so proportioned that when the handle is turned in the working direction the
frictional contact between the coned surfaces will cause the nut to be carried round
with the eye whereby the nut will tend to screw itself along the thread on the
spindle and so to wedge itself still tighter in the eye. Since the eye and nut turn
together as one, they consequently become jammed between the acting faces of the
screw thread A on the one hand and the opposing collar Don the other hand, thus
locking the handle rigidly to the spindle.
On the return or idle stroke of the handle, the nut is screwed backwards to an
infinitely small extent, until its external surface is out of tight contact with the
eye without, however, ceasing to be in frictional contact therewith, the eye then
slipping upon the nut. As the cones never cease to be in contact, the gripping
action on the forward stroke is practically instantaneous and silent.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed; I declare that what
I claim is;-
In a drill-brace, a friction clutch for transmitting motion from the handle to the
spindle, consisting of a screw thread of rapid pitch upon the spindle, a nut screwing
thereon, and of conical form externally, an eye attached to the handle fitting on
the nut and free to rotate but incapable of longitudinal motion, and a spring or
its equivalent tending to force the nut more tightly into the eye, the whole
combined for operation substantially as shewn and described.