Improvements in connection with Screw Cutting Lathes.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in connection with Screw Cutting Lathes.
I, ERNEST PARKINSON, of Canal Iron Works, Shipley, in the County of York,
Machine Tool Maker, do hereby declare the nature of this invention to be as
follows:-
The object of this invention is to arrange certain mechanism and combine same
with a screw cutting lathe in a manner that, the said lathe is enabled to cut
right and left hand screw threads on the same bar, by automatically causing the
lathe carriage to travel alternately in opposite directions; also to so mount the
cutting tools that they are automatically moved towards the work mounted
between the lathe centres before each cut commences, and away from the work
on the return of the lathe carriage; and to automatically operate the feeding of
the cutting tool to the required depth of cut to be taken at each reversal of the
lather carriage; and to arrange the said feeding motion that, when the required
depth of thread has been cut, for the feed to be automatically stopped, also to
arrange the lathe that, when cutting long screws, for the carriage, after the tool
had made a cut, to be automatically returned at a quick rate of speed to its
original position, ready for making another cut.
In carrying out my object I form a gauntry with fast and loose lathe heads as
hitherto, and in place of making what is termed the leading screw with say a
right hand thread throughout, a portion of the same may be cut with a right and
the remainder with a left hand thread, or two leading screws may be mounted on
the gauntry and utilized for travelling the carriage in opposite directions.
The carriage is mounted on the lathe gauntry, and on this carriage are two
reciprocating slides, upon each of which is mounted a compound rest or tool
holder, each slide and tool holder being automatically moved to bring the cutting
tool into contact with, and clear of the bar to be cut mounted between the lathe
centres, after travelling the length of the thread to be cut.
Each reciprocating slide is provided with a nut for engaging with the leading
screw, one nut fitting the right hand thread, and the other the left hand thread,
the reciprocation of the slides being accomplished by arms and levers in connection
with a rocking shaft which is operated at intervals, first in one direction, then
in the other, each time the cutting tool has travelled in either direction the length
of the thread to be cut.
The operation of the before mentioned rocking shaft at intervals may be
accomplished by combining with the said shaft, another shaft driven by friction
and rotated intermittently, say one half of a revolution each operation, the distance
and time of rotation being controlled by two cams or the like secured on the. last
mentioned shaft, on which is also secured a disc crank, the pin of which engages -
with an arm secured on the rocking shaft, so that, as the said disc crank revolves,.
the arm, and therefore the rocking shaft is rocked first in one direction and then
in the other, thus causing the slides carrying the tool holders to reciprocate on the.
carriage.
The automatic feeding or setting up of each cutting tool is accomplished by an
'

page_text: independent rocking shaft, to which is attached an arm provided with a pawl
which on reciprocating, engages with a ratchet wheel secured to a feed screw of
the compound rest, so that on each oscillation of the arm, the pawl propels the
ratchet wheel a certain distance, thus turning the feed screw, thereby giving feed
to the tool each time it is withdrawn from the thread being cut, or the ratchet
wheel may be operated by a sliding bar and pawl actuated by an inclined plane
or the like.
Attached to the said feed screw or ratchet wheel is an arm, which on coming
in contact with the pawl, raises same clear of the ratchet wheel, thus stopping
the feed when the thread has been cut to the depth required.
screw;
When two leading screws are utilized, long threaded screws may be cut, and
the cutting tool automatically operated in the manner as herein before described.
the nuts engaging with the leading screws, being connected together in a manner
that, when one is engaged with its leading screw, the other is disengaged with its
the operation of the reciprocating slide or slides being accomplished by
the rocking shaft actuated in the manner as herein before described. After the
cutting tool has travelled the length of the thread, the tool is withdrawn, and by
causing the return leading screw to revolve quicker than the other, or providing
the return screw with a coarser thread and running both screws at the same
speed, the carriage travels slowly during, cutting operation, but returns quickly
ready for making another cut, all the movements being accomplished auto-
matically.
In order to provide for the nuts to gear with the screw threads, in case the
threads and spaces do not correspond when the nut is brought into contact with
the screw, I provide a spring cushion which allows the nut to yield until the
threads and spaces correspond when the spring forces the nut into contact.
Dated 13 191
41 1000
Improvements in connection with Screw Cutting Lathes.
I, ERNEST PARKINSON, of Canal Iron Works, Shipley, in the County of York,
Machine Tool Maker, 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 arrange certain mechanism and combine
same with a screw cutting lathe in such a manner that, by the said lathe, right
and left hand threaded screws may be cut, by automatically causing the lathe
carriage to travel alternately in opposite directions at the same or at different
speeds; to mount the cutting tool or tools so as to be automatically moved towards
the work mounted between the lathe centres before each cut commences, and for
the said cutting tool or tools to be automatically withdrawn therefrom on the
return of the lathe carriage; also to automatically operate the feeding of the
cutting tool or tools to the required depth of cut; and to arrange the said feeding
motion that, when the required depth of screw thread has been cut, for the feed
to the cutting tool or tools to be automatically stopped.
In describing my invention in detail, reference is made to the accompanying
sheets of drawings forming part of this specification and in which
Fig. 1 represents the front elevation of certain portions of a screw cutting lathe
to which my invention is added.

page_text: Fig. 2 is a plan of a portion of the lathe gantry with traversing carriage mounted
thereon.
Fig. 3 is an end view of the lathe with the fast and loose heads and the change
wheels for operating the leading screws removed, for the purpose of more clearly
showing the carriage, a portion of which is shown in section, and the compound
rest, tool box, and other mechanism connected with the carriage.
Fig. 4 is a detached detailed back elevation of the friction motion, for inter-
mittently reciprocating the compound rest and tool box in the direction for bring-
ing the tool into contact with, and clear of the work between the lathe centres.
Fig. 5 is a detached detailed end elevation of the automatic feed motion to the
compound rest and cutting tool.
Fig. 6 is a detached plan of the same.
Fig. 7 a side elevation,
Fig. 8 a plan of the oscillating plate for stopping the rotary motion of the
friction gear, and
Fig. 9 a section through the gantry showing the mechanism employed for
stopping the friction motion for any length of time.
The detached details are drawn to an enlarged scale, and in all the figures
similar letters indicate similar parts.
In carrying out my object, I form a gantry A with fast and loose heads B
and B as hitherto, and in place of providing the lathe with one leading screw
for operating the carriage C I mount to the gantry A in suitable brackets, two
leading screws D and E which may be the same or of different pitches for travel-
ling the carriage C on the gantry A in opposite directions; I also provide a
rack and pinion of the usual construction for operating the carriage C.
The carriage C is mounted on the gantry A in the usual manner, and may be
provided with one or two reciprocating slides each supporting a compound rest
or tool holder F, and in order to simplify the drawings and description, I have
only shown one slide and compound rest, as when two are fitted to the carriage C
one slide and compound rest is a duplication of the other, and both operated in the
same manner.
The bar not shown on the drawings on which a screw thread is to be cut, is
placed between the lathe centres as usual, and rotary motion is imparted to the
leading screws D and E by the pinion G secured to the cone G¹ of fast head B
the trains of change wheels G2 and G³ are arranged in a suitable manner in
accordance with the pitch of the leading screws D and E and the pitch of the screw
or screws to be cut on the bar placed between the lathe centres.
The carriage C is fitted with two nuts of the usual construction, that is to say,
a half nut is provided for each leading screw, the nut H engages with the top
leading screw D and nut H' with the bottom leading screw both these nuts
are connected to a rocking lever one arm of which is coupled by link to the
reciprocating base slide plate of the compound rest and tool holder F. The
opposite end of the reciprocating base slide plate F is coupled by a link K to a
lever K mounted on a rocking shaft K2 between two arms C₁ of carriage C. The
rocking shaft K2 is arranged with a long key way sunk in the shaft with which a
feather key of lever K engages, and the rocking shaft is operated at intervals,
first in one direction, for causing the carriage C to travel towards the fast head B
and in the other direction, when the said carriage is to be moved back to its
original position.
The operation of the before mentioned rocking shaft K² at the required intervals
is accomplished by combining the said shaft with a short shaft L intermittently
driven by friction, in such a manner that, the said shaft is allowed to make a
portion of a revolution each time the cutting tool has travelled in either direction
the length of the thread to he cut on the bar between the lathe centres, the said
short shaft making a complete revolution each time the base slide plate F! is
reciprocated to and fro.
On rocking shaft K2 is mounted freely a constantly rotating pulley M to which

page_text: is secured a spur pinion M¹ gearing into a spur wheel M² secured on the friction
box N arranged between the friction plates N1 N1 in the ordinary manner; these
plates are secured on the short shaft L on which is also secured a double cám
plate O and disc 01, the disc having a pin P secured thereto which passes through
a block P¹ mounted in the long slot P of rocking lever P3 secured on the rocking
shaft K2 so that as the disc plate 01 is allowed to revolve, the rocking lever P³
and therefore the rocking shaft K2 are moved first in one direction and then in
the other, causing the base slide plate F compound rest and tool holder F to
reciprocate on the carriage C when required, in the direction transverse to the
length of the gantry A.
The release of the frictionally driven short shaft L at each end of thread to be
cut in the bar placed between the lathe centres, is accomplished in the following
manner-
In front of the gantry A is placed a bar Q supported at each end by suitable
brackets and by the lugs C2 C2 projecting from the vertical flange of carriage C
and in a manner that the said har may slide in its supports. On the bar Q are
two adjustable collars Q¹ Q¹ and to one end of the bar is jointed a lever R the
opposite end of the said lever being secured to a vertical spindle S passing through
bracket S attached to gantry A and to the top of said spindle is secured a plate
Shaving two projecting armis with a recess between, somewhat as shown by detail
Fig. 8.
When the base slide plate F¹ compound rest and tool holder F are at rest, one
of the notches 02 of double cam plate O, is in contact with the underside of one
of the projecting arms of plate S thus stopping the rotation of the frictionally
driven short shaft L as the carriage C is travelling on the gantry A. On one of
the lugs C coming in contact with an adjustable collar Q¹ the bar Q is propelled
along with the carriage C for some distance, by which the lever R is operated,
and the plate S2 oscillated in its bearing bracket St by which the retaining support
to the double cam plate is moved a distance so as to allow the retaining notch
of double cam plate O to pass through the opening S3 in plate S² and the said cam
plate to make a portion of a revolution; when the other notch 03 of the double
cam plate will come in contact with the underside of the other arm of plate $2
and thereby stop the rotation of the said short shaft L thus by the operation of
the bar Q in the manner described, first in one direction and then in the other,
the plate S2 is moved in unison therewith; allowing the frictionally driven short
shaft L to make a portion of a revolution each time the retaining support to the
double cam plate O is removed; allowing the pin P and block P¹ of disc O¹ to slide
in the long slot P² of lever P³ thereby causing the shaft K2 to rock in its bearings
and the lever K¹ coupled by link K to the base slide plate F¹ to reciprocate same
in. the direction for moving the compound rest F and cutting tool towards or
away from the bar placed between the lathe centres, and the nuts H and H¹ to
pass into and out of gear with the respective leading screws D and E.
The automatically feeding or setting up of the compound rest or tool.
holder F and cutting tool C³ is accomplished. by the operation of
a lever T mounted on a shaft T secured by brackets on carriage C.
The shaft T has a spirally cut key way therein, a feather key in
lever T fitting same; the upper portion of said lever is coupled by a rod U to
a lever U¹ and to the said lever is mounted a pawl U2 for engaging with and
operating the ratchet wheel W mounted on the screw W₁ by which the compound
rest or tool holder F is regulated as to position with the base slide plate F¹.
The ratchet wheel W is suitably supported by the base slide plate F¹ and
threaded to engage with the screw W₁ which passes through same; the screw bar
is extended as shown by Fig. 6 and provided with collars W2 which engage with
the upper sliding part of the compound rest in such a manner that, as the ratchet
wheel W is rotated round the screw W₁ the upper sliding part of the compound
rest supporting the cutting tool C³ is moved in one direction or the other.
When the pawl U2 is in the position for engaging with the teeth of the ratchet

page_text: wheel W the bottom end of lever U³ mounted on pin U is engaged with a notch
in arm V (see Fig. 5) and each time the base slide plate " is reciprocated in the
manner as herein before described, the lever T is slid on shaft T', and by the said
shaft being fixed, the lever on sliding over same and engaging with the spirally
cut key way, is caused to reciprocate in the direction that the pawl U engaging
with the teeth of the ratchet wheel W moves the same in a rotary direction around
the screw a certain distance, thereby operating the compound rest F and
giving feed to the cutting tool C3 before the commencement of each cut.
Between the bottom end of lever U3 and arm V is an adjustable collar Y on a
bar Y attached to upper sliding part of the compound rest F, the said collar is
so placed that, as the cutting tool C³ is moved towards the centre of the bar between
the lathe centres, the arm V is forced backwards by the said collar a certain
distance at each "setting up" of the cutting tool C3, and when the screw.thread
has been cut in the bar between the lathe centres to the predetermined depth,
the arm V will have been forced backwards a sufficient distance for the notch
therein to be disengaged with the bottom end of lever U³; thus liberating the
said lever so that by the contraction of the spiral spring Z pulling the lever U³
in the direction of the arrow in Fig. 5. the said lever on coming in contact with
the pin projecting from pawl U raises the said pawl clear of the ratchet
wheel W thus stopping the feed to cutting tool C3 when the screw thread is cut
to the depth required.
It will be obvious to persons skilled in the art of screw cutting, that if a left
and right hand thread was required to be cut on the same bar, one thread when
the carriage C was travelling in one direction, and the other thread on the return
of the carriage, two. reciprocating base slide plates F1 both mounted on the
carriage would be required, and each base slide plate provided with a tool
holder and the base slide plates coupled together by a lever of the first order, so
that on the operation of one base slide plate F¹ in one direction, the other base
slide plate will be moved in the opposite direction; or a lever of the first order
may be arranged connecting the lever K and one of the base slide plates so
that on the operation of the said lever K' the base slide plates will be moved in.
opposite directions for moving the cutting tools C into and out of contact with
the bar between the lathe centres; also the mechanism for automatically giving
and stopping the feed to the cutters, would require duplicating; and the leading
screws run at the necessary speed for obtaining the required pitches of the right
and left hand threads. When a single thread is cut on the bar, it will be readily
understood that the gearing up of the two leading screws can be so arranged so as
to give a quick return motion to the carriage C.
In order that both nuts H and H' may be retained in a position out of gear,
that is clear of the respective leading screws 1) and E I form the disc 0¹ with a
projection R in such a position that, when the sliding bar R2 is moved to engage
with the said projection, as shown by detail Fig. 9, the intermittent rotation of
the disc is stopped so long as the sliding bar R³ is engaged with the said pro-
jection, thereby holding the base slide plate in such position that the nuts H
and Hare clear of the leading screws D and E thus enabling the carriage C
to be moved by the ordinary rack and pinion.
Having now particularly described and ascertained the nature of this invention,
and in what manner the same is to be performed, I declare that what I claim
as my invention is:-
1. A screw cutting lathe in which are combined a bar Q with operative mechan.
ism intervening between the said bar and base slide plate 11 by which the said
base slide plate and cutting tool C³ are reciprocated by the said mechanism arranged
and operated substantially in the manner as shown and described and for the
purpose as herein before set forth.
2. A screw cutting lathe in which the base slide plate F1 ratchet wheel W
screw W and cutting tool (3 are combined with a shaft T¹ by intervening con-

page_text: nections arranged and operated substantially in the manner as shown and described
and for the purpose as herein before set forth.
3. The combination of the ratchet wheel W and screw W with pawl U2 lever U³
arm V and adjustable collar Y arranged and operated substantially in the manner
as shown and described and for the purpose as hereinbefore set forth.
Dated this 12th day of February 1900.
JOHN WAUGH,
Agent, Sunbridge Chambers, Bradford.