Year: 1886

page_text: We, CHARLES FAIRBAIRN of Maybank, Clarendon Road, Sale in the County of
Chester, Engineer, and MATTHEW WELLS of 61 Hardman Street Deansgate
Manchester in the County of Lancaster Oil Refiner do hereby declare the nature
of our invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
Our invention relates to apparatus whereby a piece of metal rod, which may
have a head, constituting a bolt or screw blank, being introduced between the
peripheries of helically grooved rotating rollers that are pressed towards each
other, is caused by the action of the rollers to revolve and also to travel to and fro
between them, having by this action a screw thread formed upon it. There may
be three or four rollers employed, and when there are four, these may be arranged
in either of two ways, either with their faces all nearly in the same plane, or when
the blank to be operated on is small, there may be two in one plane opposite one
another and the other two in a plane in front of so as to overlap the former. I will
describe a four roller machine and also a three roller machine referring to the
accompanying drawings. Fig. 1 is a side view of a four roller machine, Figs. 2
and 3 are end views of the front and back heads respectively and Fig. 4 is a part
longitudinal section along the axis of one of the rollers. Fig. 5 is a longitudinal
section partly in elevation, of a three roller machine. Fig. 6 is a plan partly in
section and Figs. 7 and 8 are end views partly in section of the front and back
heads respectively.
Referring to Figs. 1 to 4 inclusive, A is the framing or bed of the machine,
Ba driving shaft carrying pullies b for reversing by shifting the driving belts in
the usual way by means of forks on a sliding bar 6. This bar is worked by a
rod 63 which is jointed to a lever bs moved by a treadle b' in the one direction and
by a weight 6 in the other direction unless when it is held by a pawl 6 which
engages with ratchet teeth on the boss of the lever b³. The pawl can be
released by the inward push of a knob b7, in which case the weight 65 effects the
shift of the driving belts and thereby reverses the motion of the machine.
the shaft B is a toothed pinion 68 gearing with a wheel a on the shaft of which is
a pinion a' gearing with the external teeth of a wheel C which as seen in Fig. 4
has also internal teeth. Within the wheel C are the four pinions c, each connected
On

page_text: through a cone friction clutch c¹ to the spindle c² of one of the rollers D, the
spindles being prolonged beyond the roller to receive the support of an adjustable
bearing d, these four bearings being arranged in a plate di which is secured by
bolts to the front head E of the machine, in which also, as well as in the middle
head F, there are adjustable bearings for the roller spindles c². By adjusting
radially the bearings in E and the rollers D can be brought nearer to or farther
from one another to suit the size of the screw on which they have to operate. By
adjusting laterally the bearings f in the head F, the spindles of the rollers can be
set at a little inclination to the axial line so that their axes can be made to take a
slightly twisted altitude relatively to one another. Each of the rollers D has its
periphery grooved helically with a number of grooves inclined to its axis at
nearly the same angle as that which the thread of the screw that is to be formed
by them bears to its own axis, and the interval from groove to groove on each
roller is equal to the pitch or interval from thread to thread on the screw. We
prefer also to cross these grooves at intervals with other grooves of about the same
inclination to the opposite hand so as to present several edges that have a partially
cutting effect on the thread that is formed, rendering it more smooth and true.
The four rollers are not all of the same size; two of them, say the upper two being
somewhat larger than the other two, the lower rollers. Owing to the difference of
diameter, the obliquity of the grooves on the smaller roller is not quite equal to
that on the larger; I therefore adjust the back bearings f of the smaller rollers so
as to give their axes a slight twist, bringing the obliquity of their grooves into
correspondence with that of the grooves on the larger rollers. In front of the
machine project two guide bars g carrying a cross head G in which is held the
head of the blank, this head being placed between a front and a back cheek which
prevent the blank from moving longitudinally in the holder, while it is free to
revolve. The cross head G also carries an adjustable stop g¹ which can pass
through a hole of the front head E and butt against the pawl lever, thereby
releasing the pawl 66 and effecting reversal of the machine when the blank has
advanced sufliciently far between the rollers. In Figs. 1 and 2 the rollers D are
shewn as they would be adjusted for a screw of comparatively small diameter one
pair of them being in front of and overlapping the other pair. They need not
however overlap, but may all be in the same plane when the screw is sufficiently
large to fill in the space between their peripheries as is indicated in Fig. 7a, where
three rollers D are shewn tangential to the blank H.
The three roller machine shewn in Figs. 5 to 8 inclusive is similar in construction
to the four roller machine above described, and in these figures parts corresponding
to those in Figs. 1 to 4 inclusive are marked by similar letters. In this case the
pinion 68 on the driving shaft B gears directly with the external teeth of the
wheel C which has internal teeth gearing with the three pinions c on the spindles
of the rollers D. In the front frame E are radially adjustable bearings for the
spindles of the three rollers D which in this case overhang their bearings. In the
back head Fare laterally adjustable bearings f by which the roller spindles can be
set to the required twist. The treadle weight 65 and lever b³ work the sliding
fork bar bas already described, but instead of the pawl and ratchet wheel for
releasing the lever b³ there is a ratchet toothed lever K from the upper end k of
which projects a tappet rod ' so that an adjustable bolt m in the crosshead G
which carries the blank on butting against it moves the lever K and releases b³
allowing the weight 65 to descend and effect reversal. The blank is held in G with
.its head in the recess g³ under a hinged jaw which can be opened upwards for
insertion or removal of the blank by depressing the handle g². The recess g³ is
sufficiently large to allow the head of the blank which is generally square or
hexagonal to revolve freely.
When I employ three rollers, I make one, say the uppermost somewhat larger
than the other two, giving the spindles of the latter the twist necessary to make
the obliquity of their grooves correspond with that of those on the largest roller.

page_text: Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is
1. The construction substantially as herein described of apparatus for forging
screws by the rotation and longitudinal travel of the blank between the peripheries
of three or four rotating and pressing rollers grooved to suit the thread of the
screw to be produced.
2. In employing four rollers for forging screws of comparatively small diameter,
arranging these rollers so that the one pair that are opposite to one another overlap
the other pair, substantially as herein described.
ABEL & IMRAY,
Agents for the Applicant.