IMPROVEMENTS IN SCREW-CUTTING MACHINERY
Year: 1878

page_text: LETTERS PATENT to Willian Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for the Invention of
"IMPROVEMENTS IN SCREW-CUTTING MACHINERY." A communication from
abroad by Charles Dake Rogers, of Providence, Rhode Island, United States of
America.
Sealed the 24th December 1878, and dated the 8th November 1878.
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on. the 8th November 1878.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents
Southampton Buildings, London. "IMPROVEMENTS IN SCREW-CUTTING MACHINERY."
A communication from abroad by Charles Dake Rogers, of Providence, Rhode
Island, United States of America.
The improvements herein-after described relate to machines for cutting threads
upon screws, and are applicable to such machines as employ a cutting tool travelling
several times longitudinally along the screw to produce the thread. They have for
their object such a combination and relative adjustment of the screw-holding
spindle and the cam shaft which causes the movement of the screw-cutting or
threading tool that the number of idle revolutions, that is to say, revolutions to no
purpose, of the said spindle will be reduced to a minimum.
"
In machines of the character specified, as usually heretofore constructed, the
forward motion of the cutting tool along the screw has been produced by a screw
and nut" device, and the stoppage of the movement of the said cutting tool has
depended upon the falling of a detent into notches in a disc or plate. These notches
have been shaped, and tine has been required for the passage of the detent into
and out of the said notches, during which time the cutting tool has not been acting
upon the screw, and the screw-bolding spindle has therefore been revolving to no
useful end. Now when it is considered that every revolution or partial revolution
of the shaft operating to move the cutting tool beyond what is necessary repre-
is

page_text: sented by an exaggerated number of revolutions of the screw-holding spindle, the
latter making about twenty-four revolutions to one of the former, it will be seen
that the speed of production is very much diminished, which is a fact of considerable
importance.
To increase the speed of production is therefore the main object of these improve-
ments, and this desirable result is accomplished by means of an organization which
employs in combination a cam upon the leader shaft to move the cutting tool the
desired distance, a train of gear wheels or equivalent means to give revolution to
the leader shaft, a clutch to operate the said gear wheels, and a friction brake device
to instantaneously stop the revolution of the said leader shaft when the cutting
tool has finished its work and is in its farthest rearward position, when it is in
readiness to commence its work upon a succeeding screw at the proper point..
The said Invention consists mainly in a combination of the primary gear wheel
from which the movement of the leader is derived, the leader which actuates the
reciprocating tool post, and a friction brake to arrest the rotation of the primary
gear wheel and its connecting train at the instant the primary gear wheel is discon-
nected from the main cam shaft, whereby the number of idle revolutions of the
screw-holding spindle is reduced to only such number as will occur during the
throwing into and out of gear of that clutch gear wheel which, in machines of this
class, connects the main cam shaft with the train that drives the leader for actuating
the tool post.
In the accompanying Drawing Figure 1 represents a plan of a screw-threading
machine having these improvements; Figure 2 shows a vertical transverse section
of the same on the line x, x; and Figures 3 and 4 represent details of construction
of the said machine.
As shown in Figures 1 and 2, A represents the frame of the said machine; B,
the screw-holding spindle; C, the leader shaft; and D, the main cam shaft of the
machine upon which the clutch E is splined and the sleeve gear wheel F is mounted.
Power is applied to the spindle B and transmitted to the shaft D by a train of gear
wheels a, b, c, d, the latter gear wheel d being mounted upon the shaft D. The
clutch E is operated to give motion to and stop the revolution of the leader shaft C
through a finger G upon the shaft D, which finger, during the revolution of the
said shaft, engages with a star wheel H upon a shaft J, a cam K being mounted on
the said shaft J, the said cam operating the clutch by means of a yoke arm L. This
clutch engages with the projections e upon the disc hub f of the sleeve gear wheel F,
and through the said gear wheel and the gear wheels g, h, drives the leader shaft C.
The tool post M is mounted on the shaft M¹ which is furnished with a depending
arm N, the said arm being held against the working face of the cam O by a spring m
.or equivalent means to ensure proper motion to the cutting tool M²
Thus far has been described the mechanism used to give the cutting tool its
necessary longitudinal motions along the screw at the proper time, and were it not
for the acquired momentum possessed by the leader shaft the said mechanism would
be sufficient to stop the said tool at its proper position to commence a cut upon a
subsequent screw. This momentum being present, however, it is necessary that
some means should be devised for stopping the revolution of the leader shaft and
its cam O that the said tool may be left at the point above specified; and the
oporation of the said device must be so nearly instantaneous as to prevent the said
cam from making further revolution, and thereby changing the proper relative
position thereto of the tool post. For this purpose a friction brake is supplied, as
shown in Figures 1 and 3, and so arranged as to gripe the disc hub f of the gear
wheel Fat the proper time, thereby instantly arresting the movement of the said
gear wheel, and consequently the revolution of the cam O. This brake consists of
a flat split ring P surrounding the said disc hub f, one of the ends of the said ring
being secured to a stationary arm at Q, and the other or free end being bent at
right angles to bear against a spiral spring at R, which is seated on a screw R' to
obtain more or less compression; or the said ring itself may be a spring of sufficient
force to obtain the desired result.

page_text: : The action or non-action of this brake is made to depend upon the movement of
the clutch E, which has its yoke L supplied with a device, as at S, Figures 1, 2, and
4, the outer end of the said arm being reduced in width, and one of its acting faces
being furnished with an inclined plane s.
When the clutch is withdrawn from engagement with the sleeve gear wheel F,
and the griping force of the ring P is acting, the arm S is moved outward, and its
narrow end lies between the ends of the ring P, which are separated by a space or
distance slightly greater than the width of the arm at this point. In this relation
the device S is inert, but when the clutch is brought into engagement the arm S is
moved inward and the inclined plane s separates the ends of the ring P, thereby
increasing the diameter of the said ring and destroying its griping force upon the
sleeve gear wheel F, which latter is now free to revolve until the clutch E and its
accompanying arm S are again withdrawn, the increased diameter of the ring being
maintained and its griping force thereby temporarily destroyed during the revolution
of the gear wheel F by the increased width of the arm S at the points of engage-
ment, as shown in Figure 1.
The cam K, which acts to produce the engagement and disengagement of the
clutch E and its accompanying arm S, with the gear wheel F and ring P, is timed
to disengage 'the parts the instant the cutting tool M³ reaches its farthest rearward
position after completing its cut upon a definite screw, and to produce engagement
of the parts immediately upon the screw-holding spindle being supplied with a
subsequent screw blank, so that the said spindle is revolving to no useful purpose
only during such time as is necessary for the clutching and unclutching operations
to be performed, and as the said operations are nearly instantaneous the number of
idle revolutions of the screw spindle is reduced to a minimum.
Having now described the said improvements I will proceed to the operation of
that portion of a machine provided with the same. It being desired to cut a certain
length of screw thread the leader shaft C is supplied with a cam having the
requisite rise to move the cutting tool along the screw the proper distance. The
number of threads to the inch and the number of cuts the threading tool is to
make being determined, the trains of gearing are arranged, and a star wheel with
the requisite number of arms is used to produce the proper number of revolutions
of the shafts and the movement of the parts at the proper times. Suppose the
machine to be in operation and the tool to be making its cuts the screw-holding
spindle, leader, and cam shafts B, C, and D, and both trains of gearing will be in
revolution, the clutch being in engagement.
At each revolution of the shaft D the
finger G upon it engages with an arm of the star wheel H and moves the clutch
cam K a portion of a revolution. When the threading tool has completed its last
cut on a screw and is retreating by the force of the spring m and the contour of
the cam O, the finger G will be found in engagement with an arm of the star
wheel H and moving the cam K, which, through the yoke L, is disengaging the
clutch and allowing the brake ring P to come into force by the withdrawal of the
arm S. At the exact time when the screw-cutting threading tool has reached its
farthest rearward position, the depending arm N being then at the lowest point on
the face of the cam O, as shown in Figure 1, the disengagement of the clutch is
effected, the brake ring P is in full force upon the sleeve gear wheel F, and the
revolution of the cam O instantly ceases. A new screw blank is now supplied
while the screw-holding spindle B and shaft D are in motion, the latter making one
revolution and bringing the finger G into engagement with the star wheel H, and
through it partially revolving the cam K, thereby operating the arm S to remove
the force of the brake ring P, and moving the clutch inward to engage with the
sleeve gear wheel F. This engagement is effected immediately upon the proper
seating of the screw blank in the spindle B, and the cam O is thereby started in
revolution and the operations above described are repeated.
The feeding mechanism and other parts of the said machine not directly operating
upon the movements of the screw-cutting or threading tool are omitted in the

page_text: 'Drawing, and are not described in this Specification, they being well known and
not material to the understanding of these improvements.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent, and the manner of performing the same, I wish it understood
that I claim,
First. The combination of the primary gear wheel from which the movement of
the leader is derived, the leader which actuates the reciprocating tool post, and a
friction brake to arrest the rotation of the said primary gear wheel and its connecting
train at the instant the said primary gear wheel is disconnected from the main cam
shaft, as and for the purposes specified.
Second. The combination of the main cam shaft carrying a primary gear wheel,
from which, when it is locked to the said shaft, the movement of the leader is
derived, the leader which actuates the reciprocating tool post, the spindle shaft and
its train connecting with the cam shaft, and a friction brake operating to arrest the
rotation of the primary gear wheel and its connecting train at the instant the said
primary gear wheel is disconnected from its shaft, whereby the number of idle
revolutions of the spindle shaft are diminished, as above set forth.
Third. The combination of the primary gear wheel, from which, when connected
with the main cam shaft, the motion of the leader is derived, a friction brake
arranged to operate upon the said primary gear wheel, and a device for controlling
the brake worked by the movable clutch connecting the main shaft with the
primary gear wheel, as and for the purposes specified.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Eighth day of November, in the year of our Lord
One thousand eight hundred and seventy-eight.
117M DODT T