Year: 1886

page_text: I WILLIAM ALFRED PEARN of 23 North Road, Longsight, Manchester, in the
County of Lancaster Engineer, do hereby declare the nature of said invention, to
be as follows:-
My invention relates to mechanism for screw tapping and is or may be arranged
and used alone for such purpose, or combined with and actuated by mechanism for
drilling or boring, and consists in combinations and arrangements.
A spindle is arranged so as to be capable of revolving or being revolved and
sliding endways in suitable bearings-The lower end of this spindle is enlarged to
form a collar or shoulder and a boss forming part of a disc is fitted on the end of
the spindle being secured thereto by a screw ring or other arrangement which will
allow the bossed disc to rotate upon the end of the spindle but will prevent it from
leaving the end of the spindle or moving endways thereon.
The inner face of the said bossed disc has one two or more projections (three by
preference) which are inclined on two edges but more so on one edge, than on the
other, and these projections fit corresponding recesses on the inner face of a second
bossed disc which can slide upon a key lengthways of the spindle but cannot rotate
thereon.
A helical spring is placed round the spindle which at one end abuts against the
boss of the second bossed disc, and at the other end against a washer and screw
nut which fits a thread upon the spindle, and it is by this screw nut, that the
pressure of the spring can be adjusted as required.
The boss of the first named bossed disc is prepared to receive the end of the
screw tap to be actuated and when the spindle is rotated one way for screw tapping
the pressure of the spring gives driving power enough to rotate the tap against the
resistance opposed to it but should this resistance become excessive the inclined
recesses in the second bossed disc rise upon and pass over the projections against
the pressure of the spring and thus the rotation of the screw tap ceases while the
spindle continues to rotate until the workman stops or reverses its motion when the
screw tap is screwed out.
The projections with inclined driving edges may be reversed if desired, that is .
the projections may be on the second bossed disc and the recesses for them on the
first named bossed disc.

page_text: The screw tap is or may be round where it fits the socket for it in the bossed
disc, and it has a key-way formed in it to fit a key fixed or formed in the interior
of the socket in the bossed disc, so that the screw-tap can slide in the lengthway
of the socket but cannot rotate therein.
The socket end of the screw tap has a hole in its axis which is screw tapped to
fit the sorewed end of a small spindle having a collar on it, which small spindle
passes into a hollow in the first named spindle, which is for a part of its length
tubular..
The small spindle has an helical spring round it, and there is a nut or washer
at the upper or inner end of the small spindle which serves as an abutment for the
helical spring at that end, the abutment at the other end being against a partition
across the hollow of the bossed disc."
The spring on the small spindle serves when the screw tap, is screwed on its
lower or outer end, to draw the tap close up to the partition in the bossed disc.
When the said spindle is secured in the end of the spindle by which it is to be
rotated or in an ordinary drilling spindle, the driving spindle has only to be moved
endways by any ordinary means sufficient to enter the point of the screw tap into
the hole to be tapped, when the screw tap will automatically pass forward as the
helical spring on the small spindle will be compressed and will allow the screw tap
to be withdrawn from the socket in the bossed disc and when the screw tap has
been entered the driving spindle may be drawn back to some extent and when the
motion of the screw tap is reversed it will be screwed back into the socket on the
bossed disc, and the spring will draw it back when free from the tapped hole to be
quite clear of it.

page_text: a ring loose upon the spindle a which is screwed upon its exterior for a screw
nut a by which the spring d can be compressed to press the disc c against the
disc b.
In the inner face of the bossed disc b there are one or more notches (three
are used by preference) and on the inner face of the bossed disc c there are
projections c to correspond with the notches in the disc b. These notches and
projections are inclined on there edges as shown best in fig. 4-The spring dis
compressed sufficiently to give driving power enough to rotate the screw tap
against the resistance opposed to it but should this resistance become undue or
excessive the rotation of the bossed disc b is arrested as the helical spring d gives
way and allows the projections c¹ in one disc to escape from the notches in the
other, and thus prevents damage.
The notches may be in the bossed disc c and the projections (c¹) on the disc b if
desired.
The bossed, disc b is tubular and is prepared to fit the round end of the screw
tape to be used, which has a key groove longitudinally to fit a key 6' within the
boss (see fig. 3) so that while the screw tape will be rotated it can slide or move
endways in the boss.
.
The inner end of the screw tape has a hole in it which is screw tapped to be
screwed upon the screwed end of a small square spindle e' having a collar at its
lower end as shown.
The small spindle passes through a square hole in a partition 63 in the bossed
⚫ disc b and ascends into the tubular part of the spindle a.
The small spindle e¹ is surrounded by a helical spring e' which at its lower
end abuts against the partion 6' in the bossed disc band at its upper end against
a disc or washer e rivetted or otherwise secured upon the end of the small
spindle e¹.
The square spindle e¹ and square hole in the partition 63 is to prevent the
spindle from rotating when the tape is screwed on or off the end of the spindle,
the tap being screwed on to the end of the spindle when it is drawn down and
held below the end of the boss b by inserting a forked piece x so that its two
prongs will pass one on each side of the spindle e' above the small collar upon it
and between the collar and the end of the boss b (see fig. 6)-When the tap is
secured the fork is removed.
.
With this arrangement it will be seen that the small spring e³ will act constantly
to draw the inner end of the screw tap c towards and against the partition b³.
In using this mechanism for screw tapping it will only be necessary to move or
screw out the drill spindle (if used in a drilling machine) until the point of the
screw tap enters the hole to be tapped; then the end motion of the drill spindle
may cease and the screw tap will be drawn automatically out of the boss b, as the
screw enters the hole and forms the thread, and when the screw, tap can go no
further the spring d will allow the projections c¹ on one bossed disc to be released
from the notches in the other bossed disc and when this takes place the workman
reverses the rotation of the drill or other spindle and thus unscrews the screw tap
out of the tapped hole and as it unscrews, the tap moves back into the boss b and
the spring e also draws it back into the boss b, and while this is taking place or
before the workman screws back the drill or other spindle sufficiently to allow
clearance for the point of the screw tap when fully screwed out and this allows
the spring e to draw back the screw tape suddenly for a short distance when
released from the hole, which has been tapped which will cause a slight blow of
the upper end of the tap against the partition 63 and this throws or shakes off any
metal or dirt adhering to the screw tap leaving it clean for the next hole to be
operated upon.
"
It will be understood that in using the mechanism above described the spindle
which actuates the spindle a is driven by belts or gearing so that the driving
spindle can be rotated in both directions, one way for screwing the tap into, the
hole, and the other for screwing it out, and the driving spindle must be able to

page_text: move endways in both directions as in ordinary drilling and screw tapping
mechanism.
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 combination and arrangement of the mechanism substantially as and for
the purpose hereinbefore described and illustrated by the drawings.
2. The combination and arrangement of the spindle (a) bossed discs b and c,
spring (d) and screw nut (a) for giving rotary motion to screw taps, substantially
as and for the purpose hereinbefore described and illustrated by the drawings.
3. The combination of a screw tap arranged to slide endways in or on the end
of the spindle or boss giving it rotary and end motion and connected with a spring
for drawing the screw tap towards the driving spindle or boss substantially as and
for the purpose hereinbefore described.