IMPROVEMENTS IN SCREWING MACHINERY
Year: 1876

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake, &
Co., Patent Agents, Southampton Buildings, London, for the Invention of
IMPROVEMENTS IN SCREWING MACHINERY." A communication from abroad
by Frank P. Sheldon, of Providence, Rhode Island, United States of
[1
America
Sealed the 3rd March 1876, and dated the 12th January 1876.
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of Commissioners of Patents.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. « IMPROVEMENTS IN SCREWING MACHINERY."
A communication from abroad by Frank P. Sheldon, of Providence, Rhode Island,
United States of America.
This Invention appertains to that class of screw making machines which employ
dies for cutting what are called "fine threaded" or machine screws, as distinguished
from coarse threaded wood screws, in which the thread is cut by a reciprocating
chasing tool.
The first part of the said Invention relates to means for insuring the presentation
of the blank to be threaded to the stationary griping and holding jaws, so that
the nick or slot in the head of the blank will always stand perpendicularly to the
acting faces of the jaws, thereby affording the greatest resistance of the head to
the gripe of the jaws, and keeping the head from being crushed, as it is liable to be
in machines of this class, in case the blank is held with the nick standing parallel
to the planes of the faces of the jaws; other features of the said Invention are
herein-after specified.

page_text: omitted for the sake of clearness, and also because that part of the machine is
already well known.
Figures 2, 3, 4, 5, 6, 7, 8, are views of details of the machine, showing the special
points for more fully illustrating my Invention.
Figure 9 is a plan of the said machine drawn to a reduced scale.
A is the rectangular bed or table of the machine. Some one of the many
known automatic feeding devices must be employed, so that a single blank a,
Figure 3, is able to be seized by the spring fingers b, Figure 1, whose office is to
pre ent the same to a pair of griping jaws to be by them held while the operation
of cutting the thread is being performed by a revolving die. Supposing now that
a blank a, Figures 1 and 3, has been taken by the fingers, the first operation is for
the fingers to move laterally toward a revolving yielding screwdriver c. This movement
is effected by means of a spring d on the finger shaft B controlled as to time by
the revolving cam c; the same tinger shaft B being capable of a slight end wise move-
inent on its bearing, tho extent of which can be adjusted by the screw gauge C.
The screwdriver c has its construction clearly shown at Figure 5. It is arranged
to make at least one completo revolution in its bearing f, while the blank is pre-
sented to it by means of the bevil gear wheels g, g, driven by a gear wheel D on the
principal cam shaft, Figure 4. As the screwdriver rotates it will be able at the
same time to spring into the nick of the blank and cause the blank itself to rotate
until such time as the side cam c moves the finger shaft, and consequently tho
fingers away from engagement with the screwdriver. The action of the cam c is
timed to leave the blank when withdrawn from the screwdriver with its nick
standing in the proper position required to best withstand pressure when seized by
the griping jaws; the fingers are now permitted to carry the blank in front of the
griping jaws E. These are stationary holding clamps adapted to seize the blank
by the head and hold it firmly, and are made to perform this office of seizing and
holding the blank and releasing it after it has been screwed by their combination
with toggle levers E', sliding sleeve E, and revolving scroll cam E³.
The next operation to be performed is that of threading the blank; this is done
by a die F mounted on an arbor F', which is made to revolve first in one direction,
while tho die is cutting the thread, and then in the reverse direction to enable it
to back off from the screw so made. There is nothing now in this operation and
the machinery by which it can be performed is familiar to all constructors of screw
machinery. In this instance the side cam G, Figures 3 and 4, acts upon an arm G',
Figure 3, set on the shaft G, which latter is arranged on bearings so as to have an
endwise movement. The forward movement so given to the shaft G is communi-
cated by means of the arm G and adjustable screw head & to the die arbor F', and
the latter is thereby moved far enough to bring the die up to the blank. The
cam G continues to revolve for a sufficient length of time (acting now as a leading
cam with an inclination of face corresponding with the pitch of the threads on the
die) to enable the thread to be well started when it ceases its action, and tho
spring i throws the shaft G to the position shewn at Figure 3, the die continuing
its work.
The next part of my Invention relates to the means by which the machine can be
adapted at pleasure to cut different lengths of thread, and perform promptly the whole
sequence of operations necessary to the screwing of a blank without being obliged
to wait for any member of the machine to "come to time," in case the machine is
Ecrewing the shortest blank beyond what would be necessary in caso it were
screwing the longest blank.
In machines of this class as hitherto constructed, it is required in order to cut
serews of different lengths to make changes in the cams or gear wheels or both,
involving a great loss of time and complicating the machine with a large number
of change gear wheels. The device, herein-after described, is independent of the
rest of the machine and may be applied to any screw machine when it is
desired to regulate at will the length of the thread to be cut. The die arbor or

page_text: spindle F is caused to rotate alternately in opposite directions by means of the
gear wheels II, HI, which are constantly revolving in opposite directions and
receive motion from the driving shaft H, to which power is applied through an
intermediate gear wheel. The changes in the direction of rotation in the die arbor
are effected by means of a shifting clutch I, which is capable of sliding on the
saine shaft upon which the gear wheels H, I, are mounted, and is made to engage
with the one or the other by means of clutch pins. This clutch is connected with
the shaft by means of a spline. Necessarily the gear wheels H, H, are made to
revolve around their shaft except at such times as they are respectively locked
therewith by means of the clutch 1, which always revolves with the shaft and
consequently the die arbor will be rotated in one direction or the other by means
of the gear wheels J, J, according as the clutch I has locked the shaft with the
one or the other of the gear wheels H, H'.
As already stated the die arbor F must have a longitudinal movement in its
bearings to enable the die which it carries to traverse the part of the blank to be
threaded, and consequently the connection of the die arbor with gear wheel J¹
must be by a spline.
To determine the length of time that the die arbor shall rotate in the direction
to enable the die to cut a thread, and to fix the time when its direction of rotation
shall be reversed there are employed the herein-after next described devices and
combinations of instrumentalities. 1, Figure 3, is a sliding bar mounted, in
suitable guides in a frame , and is capable of a limited endwise movement, the
extent of which can be regulated by adjustable stops. Upon the under side of this
bar are two brackets,, in which the adjusting screw rod is mounted. The
bracket projects downward lower than its fellow and this extended portion
forms an ear piece, which, with its fellow L, the latter being mounted on the screw
rod so that its distance from can be regulated at pleasure, constitute in combi-
nation with a collar or equivalent device on the die arbor a part of the means for
changing the direction of rotation of the die arbor. Upon the die arbor or spindle Fi
it will be observed there is placed a collar M, which is adjustable and which will
partake of all the movements of the spindle, and will at some time during the
forward movement of the die arbor, while the die F is cutting a thread, come
into contact with the ear piece L, and will also during the reverse movement of
the die arbor induced by the die unscrewing from the thread which it has cut come
into contact with the fellow car piece l².
Upon the upper side of the sliding bar is an elevated section m having two
inclined approaches, and also two spring latches n, In combination with the
upper side of the sliding bar are two levers N, N, Figure 3, having their fulcruins
at n,, Figure 1. These levers are placed at such distance from each other and
in such a relation to the inclined approaches and spring latches above mentioned,
that it is impossible for more than one of the levers to be resting upon the lower
level of the 'upper surface of the sliding bar at the same time. From the ends of
the levers N, Ni, depend two pins e, o, Figure 3, by means of links of, and play
loosely in guides in a block O, which is free to slide laterally upon a stud pin pre-
jecting from, the frame of the machine. Underneath this sliding block is a double
faced rotating cam P, which as it revolves will come into contact with that one of
the pins o, o, which lies at the moment within its path of rotation, and con-
sequently will cause the block to slide on its stud support to the right or to the
left. This block carries a clutch shifter Q, which controls the clutch wheel J, and
thereby the direction of rotation of the die arbor.
From the foregoing description of the elements which compose this part of the
organization of the machine, it will be understood that the general mode of
operation is as follows:-Suppose the die F to be cutting a thread upon a blank
held by the jaws, the clutch I and the die arbor are being driven by the gear
wheel H. When the die arbor has traversed so far forward as to bring the collar

page_text: M in contact with the adjustable ear piece L, the sliding bark will then commence
to slide in the same direction with the die arbor. This action will cause the
lever N to ride up the inclined approach to the elevated section m of the sliding
bar, the spring latch n allowing this to be done. By this movement the pin o
has been lifted clear of the revolving cam P. The continued forward movement of
the sliding bar will next cause the fellow lever N to drop from the abrupt face of
the spring latch n, whereby the pin o will drop within the path of rotation of the
cam P, and as a consequence of this the clutch I will be shifted from engagement
with the gear wheel H into engagement with the gear wheel H, when a reverse
movement of the die arbor will cominence.
It is obvious that the time during which the die arbor shall rotate in the direction
to enable the die to cut a thread, and consequently the length of the screwed
portion of the blank is under complete control by simply adjusting the collar M
and the ear piece L properly with reference to each other. While the die is
unscrewing from the screw the die arbor and its collar are moving longitudinally
backward, and when near the end of its movement the collar M comes into contact
with the ear piece, thereby causing the lever N and its pin o to be raised and
the pin o' to be lowered to engage with the cam P, and thus change the direction of
the rotation of the die arbor.
It will be obvious to constructors of screw machinery that the means above
described can be applied to screw cutting machines in which the screwing die does
not revolve, but in which the die has only a to-and-fro movement and the blank
alone is revolved.
To give room between the face of the die and the holding jaws for the insertion
of another blank a lover R, Figures 1, 2, and 3, actuated by the force of a spring or
weight, presses against the face of the collar M and slides the die arbor farther
backward in its bearings so soon as the die has backed from the screw which has
been cut.
Another feature of my Invention resides in the fact that the devices. by which
successive blauks are fed to the machine are permitted to remain at rest while a
screw is being cut, but are started the instant the finished screw is ready to be
discharged.
The cams from which the necessary motions are obtained are shown in Figure 4,
and are all attached to a hollow shell S that surrounds a shaft S', which is in
constant revolution by gearing S deriving motion from the driving shaft through a
train of gear wheels. The shell S is held locked when not in motion by means of
spring arm S, Figure 2, which engages with a notch in the cam St.
A sliding clutch T, Figure 4, constantly revolving with the shaft S¹, and con-
nected therewith by a spline, serves at the proper time to give motion to the cams.
It is thrown into engagement with the can shell S by means of the spring which
constantly presses against its shifter T, and it is thrown out of engagement by the
cam faces which at each revolution of the shell acts against a projecting lug s¹ on
the side of the shifter. The clutch is held out of engagement with the cam shell
after the cam last mentioned has performed its office by means of a stop t set on
the frame of the machine, with which a catch pin u, Figure 2, engages. This catch
pin is set loosely in a socket hole through the shifter, and is connected by a link to
the end of the long arm of the lever U. The shorter arm of this lever is so located
as to interfere with the path of the backward movement of the collar M on the die
arbor when the latter is acted upon by the lever R for the purpose, as above
explained, of moving the screwing die away from the jaws far enough to allow for the
insertion of a new blank. The back edge of the collar M is beviled so as to present
an inclined plane to the side of the short arm of the lever U, and consequently the
backward movement of the collar will by depressing the shorter arm of the lever
raise the catch pin u and allow the spring to cause the clutch to engage with the
cam shell.
From this description it will be undersoodt that the backward movement of the

page_text: die arbor which occurs just as the finished screw is ready to be discharged from the
holding jaws indicates the time when the feeding devices are to again be put into
operation, and thereby any idle running of the machine to bring the feeding devices
to time in case the machine is cutting short instead of long screws is avoided.
After a new blank has been inserted in the jaws, and after the cutting die has
taken hold of the same, the completed revolution of the cam shell causes the cam
faces to open the clutch gear, when nothing being in the way to prevent it the
catch pin u will fall into engagement with the stopt and the cam shell will remain
at rest.
As a result of the construction last described if from any cause there is a failure
to present a blank to the jaws the die arbor will immediately afterward be moved
to its extremne backward limit by the spring lever R, and consequently the feeding
device will be at once put again into operation without waste of time, and the
attendant can always tell from a distance whether the machine is performing all its
functions in their regular sequence by observing whether the feeding fingers are in
continuous movement. If they are he knows that the machine is not screwing
blanks.
The device shown in Figure 6 is designed to diminish the severity of the blow
on the gear wheels when the direction of rotation of the die arbor is reversed. It
consists essentially of a friction brake formed of two bands of leather held in two
semicircular pieces of metal which enclose the pulley V secured to gear wheel J,
Figure 1. The brakes are pressed together by a spring v, Figure 6. They are
jointed together and attached to a rod w which passes through a hollow stand W
fastened to the frame of the machine. The rod w is encircled by two spiral springs
of equal length and tension which press in opposite directions against the washers
on the rod. The normal position of the brakes when the pulley V is stationary
will be such that the springs are both equally closed. So soon as the pulley revolves
in either direction the friction of the brakes will cause the rod to be moved in one
direction or another, compressing one of the springs until the tension of that spring
is suflicient to balance the friction of the brakes. As soon as the clutch is disengaged
from the gear wheel which is driving it this spring will suddenly be relieved and
will act upon the rod and pulley V and start it in the opposite direction before the
clutch has engaged with the other gear wheel, so that when it does so engage with
the gear wheel which is rotating in the opposite direction the blow on the gear
wheel and clutch pins will be very much lighter; and thus the machine will work
much more smoothly, and there will be less liability of breaking wheels than
would be the case if the clutch were suddenly thrown into a contrary motion with-
out preparation.
The device shown in Figure 7 is designed to insure the discharge of the finished
screw from the jaws in case it binds in either jaw from the effect of the severe gripe
to which the blank is subjected. A bifurcated plate of thin metal z, Figure 1, is
attached rigidly to the head of the mandril which contains the jaws, and so that the
two legs will act as stops to interfere with the screw as it is moved in the are of a
circle by the jaw to which it binds as such jaw is opening, and thus will be stripped
from the jaw.
The bifurcated piece x may be made movable to be drawn out of the way of the
dies when cutting a thread close up to the jaws, and be brought into action only
just as the jaws open; or a spring behind or between the jaws to press upon the
head might answer the purpose in some cases, but the form shown in the Drawing I
consider the most effectual and positive.
Another difficulty in die machines which cut a thread nearly the whole length of
the blank is that the chips of iron caused by the die will lodge on the jaws, and
when they open will find their way into the recess which fits around the head of
the blank, and when the jaws again close upon a blank the head will be bruised by
such chips and become spoiled. This difficulty has been overcome (but only very

page_text: imperfectly) hitherto in hand machinery by wiping out the jaws by hand after the
cutting of every scrow.
I make uso of a stream of some suitable liquid, which is delivered from a pipe y,
Figure 3, upon the outer surface of the jaws before they open, thus washing off the
chips which have lodged thereon, so that when the jaws open there will be no chips
there to fall in. I make use of oil, because the stream of oil is necessary for lubri-
cating the dies in cutting the thread, and by having the oil pipe hung on a swivel
joint, and pressed against the head of the die spindle by a spring it serves the
double purpose of lubricating the dies and washing the jaws.
Having thus fully described the said Invention, as communicated to me by my
foreign correspondent, and shown how the same may be conveniently and advan-
tageously carried into practice, I wish it understood that I do not limit myself to
the precise construction and arrangement of the several parts of the machinery
composing the subjects of this Invention, as above described, but intend to include
all mere variations or modifications of structure and arrangement for accomplishing
the purpose of the said Invention, and I claim,--
First. The combination of the instrumentalities for causing the nick in the head
of a screw blank to be set in a given position before presentation to the holding
jaws, that is to say, a suitable feeding mechanism for selecting blanks one by one,
holding jaws, and a revolving blank turner, as above described.
Second. The combination of the spring fingers capable of a sidewise movement
with a revolving blank turner for enabling the screw blank to be engaged with the
blank turner, and afterward disengaged therefrom, as above specified.
Third. The combination of the instrumentalities for changing the backing-off
motion after the screw is clear of the dies to the motion for screwing the next blank,
that is to say, an adjustable collar partaking of the longitudinal movement of the
die holder, a shifting clutch operated by suitable mechanism, and the revolving gear
wheel inducing by suitable gearing the requisite rotation for cutting the screw
thread, as above specified.
Fourth. The combination of a sliding bar, having ear pieces, an adjustable collar
partaking of the longitudinal motion of the die holder, a shifting clutch operated
by a cam, and alternately engaging pins at times determined by the said sliding
bar and collar, and gear wheels revolving in opposite directions, as above described,
for the purpose of automatically changing the direction of rotation of the die
arbor.
Fifth. The combination of the sliding bar constructed as described, the levers, and
the spring latches, substantially as specified, and for the purpose set forth.
Sixth. The combination of the adjustable collar partaking of the longitudinal
motion of the die holder with the system of cams on the hollow shaft by means of
a vibrating clutch gear connecting such shaft with the source of motion, and the lever
controlling a stop catch, whereby the said cam shaft may be stopped while a blank
is under the action of the cutting die, and started again after a blank has been
discharged from the jaws, or in case a blank has not been presented to the die, as
above described.
Seventh. In combination with the gear wheels, whose direction of rotation is
alternately changing, to reverse the motion of the die arbor, the friction pulley, and
double-acting spring brakes for giving an easy initial movement to the gearing for
changing direction, as above specified.
Eighth. The combination in an automatic screw threading machine of the bifur-
cated discharger, the griping jaws, and the feeding fingers, arranged and operating
together as above described, whereby the finished screw is ejected from the jaws,
and the way cleared for the advance of the fingers with a blank, as above set
forth.
Ninth. The combination, as above described, of the feeding fingers with the
stationary holding jaws when the latter are arranged to open in a plane intersected
by the path of movement of the fingers, whereby the blank can be presented to be

page_text: griped by the jaws without the requirement of any sidewise movement on the part
of the fingers.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Twelfth day of January, in the year of our Lord One
thousand eight hundred and seventy-six.
Witness,
JAMES EDWARDS,
8, Southampton Buildings,
London.
W. ROB. LAKE. (L.S.)