Improvements in Machines for Threading or Tapping Screw Nuts.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Machines for Threading or Tapping Screw Nuts.
I, FRIEDRICH AUGUST MEISCHNER, Mechanical Engineer, of Zschopauerstrasse,
Chemnitz, in the Kingdom of Saxony, do hereby declare the nature of this inven-
tion to be as follows:-
This invention relates to automatic machines for tapping or threading screw
nuts, and more particularly to the type described by my Patent Specification
No. 1816, dated 25th January 1896.
The mechanism specified by Claim 2 of the said specification is incomplete,
in as much as it is only suitable for performing a partial process, the regular
thread-cutting process, but as the process of tapping screw nuts, like other
elementary working processes, is composed of three partial processes viz. the
starting or cutting-in process, the regular cutting process, and the cutting-out or
releasing process, I have constructed mechanism suitable for performing these
three consecutive operations.
The screw tap or tapping spindle is held fast, so that it can neither turn nor
shift, and the threaded part of the spindle is surrounded by an internally screw-
threaded nut-holding sleeve, the threads of which are steep and uniform in the
lower part of the sleeve, while in the upper part they are intermittent. The
pitch of the uniform or ordinary screw-threads is equal to that of the intermittent
screw-threads, and the latter form the continuation of the former, the cross section
or profile of which has a shape, that they touch a low prism, such as a hexagonal
or square nut on both sides, without appreciable clearance, that is to say, the front
faces of the screw threads touch the top edges of the prism (viz. the highest nut to
be tapped) on the left side, while the rear faces of the screw threads touch the
bottom edges of the same prism on the right hand side).
The intermittent threads differ from others by the fact, that each thread forms
on one side a series of steps, and that the horizontal faces of corresponding steps
of different threads are level with each other, viz. in the same horizontal plane.
The vertical sides of the steps touch the prismatic faces of the nut, while the
horizontal faces of the steps touch the top face of a nut.
On the internally threaded nut-holding sleeve described above there are mounted
a pair of rings held apart by a helical spring, viz. an upper ring, which is loose on
the sleeve and abuts against a shoulder of the same, and a lower ring, which is
screwed fast a short distance above the lower end of the sleeve.
The upper ring is provided on its outer surface with steep screw-threads, or
helically inclined lugs, which project into helical grooves formed on the inner
surface of an outer sleeve or casing, which is situated in the interior of the tubular
driving shaft and coupled together with the same. The inside of the said outer
sleeve has two annular steps or shoulders, one of which is situated at its lower
end and serves as a support for a helical spring which presses with its upper end
against the lower ring mounted on the nut-holding sleeve.
The screw threads or lugs formed on the upper ring as described above, are
helically inclined also at their upper face or edge, to correspond with helically

page_text: inclined teeth projecting downward from a stationary disc connected with the
tap holder or device for fixing the tapping spindle.
The apparatus operates as follows;-
1
The outer sleeve coupled together with the tubular driving shaft (and situated
within the same, as mentioned above) transmits its motion to the upper ring
(through the steep threads of the same) and the nut-holding sleeve, and as long
as there is no screw nut subjected to the working process, the revolving nut-
holding sleeve is pressed upward by the helical spring acting on the lower ring,
as mentioned above. The upper ring, however, is periodically pressed downward
by the stationary teeth mentioned above, and transmits these periodical down
motions to the nut holding sleeve through the intermediary of the helical spring
inserted between the upper and lower ring. If now a fresh nut arrives from above
in the nut-holding sleeve running without load, the sleeve presses with the
horizontal faces of the corresponding steps (those which are on the same level)
upon the top face of the nut, whereby the nut is pressed against the cutting edges
of the tap, while the prismatic faces of the same set of steps lay themselves
against the prismatic faces of the nut and impart rotary motion to the same.
These operations produce the first part of the working process, viz. they start the
cutting process. The nut-holding sleeve no longer takes part in the periodical
downmotion of the upper ring, but moves downward with the nut, according to
the inclination of the screw thread of the screwing tap, while at the same time
revolving; as the nutholding sleeve presses with its shoulder on the upper ring,
the latter is no longer subjected to the pressure of the stationary teeth, but slides
with its outside threads along the steep helical grooves of the outer sleeve, as far
as may be necessary to follow the inclination of the thread of the screw taps, and
until the said outer threads arrive at the lower ends of the helical grooves. In
this manner the regular cutting of the thread, or the second stage of the working
process takes place, while the lower helical spring is being compressed. The
resistance to the cut has already become so small, that the upward pressure of the
lower helical spring overcomes the friction between the nut and the nut-holding
sleeve which hitherto has caused the down-motion of the cutting sleeve, and con-
sequently forces the entire cutting mechanism back into the starting position
suitable for receiving a fresh piece of work.
During the cutting out or releasing process of the nut, which has been tapped,
the latter slides with its prismatic faces along the threads of the nut-holding
sleeve, until it drops off the tap.
The supply or feed of the nuts may be so arranged, that the starting process of
one nut coincides with the releasing process of another.
For holding the tap I employ the device represented by the accompanying
drawings, Fig. 1 being an elevation and Fig. 2 a plan of the same.
As shown by Fig. 2 the screwing tap is held at two points by two systems of
levers placed one above the other, the upper system of levers forming a quadri-
lateral A B CD, and the lower system a quadrilateral A'B'C' D¹, (in Fig. 2 the
side BC is broken off, in order to show the parts situated underneath).
The side A B (AB) is composed of two short lever arms AE (A' E¹)
and BE (BE), which are rigidly or almost rigidly connected respectively with
the lever arms AD (AD) and BC (BC), so as to form angle levers EA D
(EAD) and EBC (E¹ B'C') adapted to turn on stationary pivots. The said
pivots form parts of two spindles d, d screwed into a base plate c or into the
machine frame. The ends C and D (CD) of the angle levers are coupled together
by pins with the forked eyes of a rod CD (CD), so that the two levers are forced
to turn in unison. The contact surfaces at the point E (E) are partly prismatic
or flat and partly cylindrical, two parallel faces of the tap spindle being so enclosed
by the arms AE (A' E) and BE (BE), that each arm touches a prismatic and
a cylindrical face of the spindle, and allows the coupled angle levers to turn in
one direction. Each of the spindles d, d has a square portion v (the drawing only
shows that of the right hand spindle, the other being covered by a lever A-D)

page_text: on which is fixed one end of a spiral spring for f, while the other end abuts
against a studs or s¹ mounted on one of the levers, the spring being thereby kept
at the required tension. The tap holder or tool holder acts as follows:-
The spiral springs f, f¹ press the arms AE (A' E¹) and BE (B¹E¹) of the angle
levers against the tap spindle, so as to prevent it from turning and shifting, but
the tension of the said springs is not strong enough to keep the toolholder closed,
in case the cutting resistance increases to a dangerous limit, where the tap would
be liable to break. In case of such an increase the tap spindle turns between the
cheeks of the holder and finally drops out of the same, after which the system of
levers yields to the springs, until the arm B E (B, E₁) lays itself against the
arm A E (A, E₁) or until the link CD (CD) lays itself against the arm BC (B' C¹).
For mounting the tap in the holder, the angle levers are turned in opposition
to the springs f f¹, so as to form sufficient clearance between the jaws of the
arms AE (AE) and BE (BE) for inserting the tap in its original position.
Instead of springs f f', weights may be used in combination with suitable lever
mechanism for pressing the jaws of the holder against the tap spindle.
In the accompanying drawings the principal parts of the holding device are
shown in duplicate, and the corresponding parts of the two holders are designated
with the same letters of the alphabet, but distinguished by indexes. Each of the
coupling rods CD (CD) is provided on the outside with a tooth z (¹), and a
tooth-wheel r placed between the two coupling rods carries a pair of studs n, n³, one
of which extends upward and the other downward from the toothwheel.
If the wheel turns on its axis, the two studs act alternately upon the teeth z
and and produce in conjunction with the springs f, f¹ the alternate opening and
closing of the two tap holders, in consequence of which the screw nuts may be
caused to slide along the tap spindle and released from the same, without releasing
the tap from the holding device.
Dated this 9th day of March 1898
FAIRFAX & WETTER,
Agents for the Applicant.
I, FRIEDRICH AUGUST MEISCHNER, Mechanical Engineer, of Zschopauerstrasse,
Chemnitz, Kingdom of Saxony, German Empire, 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:-
This invention relates to automatic machines for tapping or threading screw-
nuts, and more particularly to the type described by my Patent Specification
No. 1816, dated January 25th 1896.
The mechanism specified by Claim 2 of the said specification is incomplete, in
as much as it is only suitable for performing a partial process, namely, the regular
thread-cutting-process, but as the process of tapping screw-nuts, like other
elementary working process, is composed of three partial processes, namely the
starting or cutting-in-process, the regular cutting-process, and the cutting-out
or releasing process, I have constructed mechanisms, suitable for performing these
three consecutive operations.
These mechanisms comprise those for holding or mounting the screw-tap and
those for moving the nut over the same. The screw-tap is mounted in such a
manner, that the nut to be threaded may be shoved upon the tap at one end of
the same and may leave it at the other end, so that the nut passes over the whole
length of the screw tap.

page_text: The latter is held fast, so that it can neither turn nor shift, and the threaded
part of the screw-tap or tapping-spindle is surrounded by an internally screw-
threaded rotary box, the threads of which are steep and uniform in the lower part
of the box, while in the upper part they are intermittent. The pitch of the
uniform or ordinary screw-thread is equal to that of the intermittent screw-
threads, and the latter form the continuation of the former, the cross-section or
profile of which has such a shape, that they touch a low prism, such as a hexagonal
or square nut, on both sides, without appreciable clearance, that is to say, the
front faces of the screw-threads touch the top-edges of the prism (viz. the highest
nut to be tapped) on the left side, while the rear faces of the screw-threads touch
the bottom edges of the same prism on the right side.
The intermittent threads differ from others by the fact, that each thread forms
on one side a series of steps, and that the horizontal faces of corresponding steps
of different threads are level with each other, namely in the same horizontal
plane. The vertical sides of the steps touch the prismatic faces of the nut, while
the horizontal faces of the steps touch the top-face of the same.
On the internally threaded box afore mentioned is mounted a collar and a
sleeve, held apart by a helical spring; the sleeve is loose on the box and abuts
against the shoulder of the same, and the ring is screwed fast a short distance
above the lower end of the box.
The sleeve is provided on its outer surface with steep screw-threads or helically
inclined lugs which project into helical grooves formed on the inner surface of an
outer casing which is located in the interior of the tubular cutting-spindle and
coupled together with the same. The inside of the said outer casing has two
annular steps or shoulders, one of which is situated at its lower end and serves
as a support for a helical spring which presses with its upper end against the lower
ring mounted on the rotary box (see Figure 3).
The screw-threads or lugs formed on the upper sleeve are helically inclined also
at their upper face or edge, to correspond with helically inclined teeth projecting
downward from a stationary disc connected with the tap-holder or device for fixing
the tapping-spindle.
The outer casing coupled together with the revolving cutting-spindle transmits
its motion to the upper sleeve (through the steep threads of the same) and the
rotary box, and as long as there is no screw-nut subjected to the working process,
the revolving box is pressed upwards by the helical spring acting on the lower
ring, as above mentioned. The upper sleeve, however, is periodically pressed
downward by the stationary disc above mentioned, and transmits those periodical
down-motions to the rotary box through the intermediary of the helical spring
inserted between the upper sleeve and the lower ring. If, now, a fresh nut arrives
from above in the rotary box running without load, the box presses with the
horizontal faces of the corresponding steps (those which are on the same level)
upon the top-face of the nut, whereby the nut is pressed against the cutting edges
of the tap, while the prismatic faces of the same set of steps lay themselves
against the prismatic faces of the nut and impart rotary motion to the same.
These operations produce the first part of the working process, namely they start
the cutting process. The rotary box no longer takes part in the periodical down-
motion of the upper ring, but moves downward with the nut according to the
inclination of the screw-thread of the screwing-tap, while at the same time
revolving; as the rotary box presses with its shoulder on the upper sleeve, the
latter is no longer subjected to the pressure of the stationary disc, but slides with
its outside threads along the steep helical grooves of the outer sleeve, as far as
may be necessary to follow the inclination of the thread of the screw-taps, and
until the said outer threads arrive at the lower ends of the helical grooves. In
this manner the regular cutting of the thread, or the second phase of the working
process takes place, while the lower helical spring is being compressed. The
resistance to the cut has already become so small, that the upward pressure of the
lower helical spring overcomes the friction between the nut and the rotary box,

page_text: which hitherto had caused the down-motion of said box, and consequently forces
the entire cutting mechanism back into the starting position suitable for receiving
a fresh piece of work.
My improved machine for threading or tapping screw-nuts is represented in
the acompanying drawings, in which
Figure 1 is a vertical longitudinal section through the main working parts of
the machine,
Figure 2 is a plan of the mechanisms for holding the screw-tap.
Figure 3 is a side-view partly in section of a slightly modified form of con-
struction, the modifications referring especially to the mechanisms just mentioned.
Figure 4 is a plan of said mechanisms.
Figure 5 is a longitudinal section through the rotary box mentioned in the
preamble.
Figure 6 shows the rotary box combined with some other parts already men-
tioned, and being just about to move a nut over the threaded portion of the
screw-tap.
Figure 7 is a longitudinal section through the wall of the afore mentioned
box.
Figure 8 is a horizontal section through the same, and
Figure 9 is a plan of the said box with its neighbouring parts.
The mounting-device for the screw-tap consists of four bell-crank-levers having
each a short arm band a long arm 6. These levers are arranged in pairs, and the
arms of each pair are connected by links cc having each a lateral projection.
The levers are fulcrumed upon pivots a projecting from a base-plate h, and the
arrangement of said pairs of levers upon said pivots is such, that one pair is
located above the other and the two short arms (b) of each pair move simultaneously
in opposite directions, when the arms b¹, or the connecting link c or care or is
moved in one or the other direction. In the position shown in Figures 2 and 4,
the lower arms b have left the screw-tap A, but the upper arms b₁ (one of the
upper levers is left away in these figures in order to represent more distinctly the
position of the respective lower lever at that time) have grasped the screw-tap
between them, so that the latter remains in proper working position.
In order to continually secure the screw-tap in this position, it is, of course,
necessary that the screw-tap is always held by at least one pair of the lever arms b,
and each pair of levers should, therefore, be opened only after the other pair has
been closed. To effect such a manner of operation of the levers, I prefer to make
use of a rotary disk C having two projections or pins 3, the latter are located upon
diametrically opposite sides of the disk C, and one pin extends in an upward, the
other in a downward direction. The plane of the disk C is located between the
planes of the pairs of levers afore described, and the position of the projections_c²
of the connecting links c c¹ of said levers is such, that the lower projection may be
actuated by the lower pin (3), whereas the upper projection may be actuated by
the upper pin. The direction of rotation of the disk C is opposite to that of the
hands of a clock, and the disk C or the pins 3 of the same respectively, do not,
therefore, effect the closing of the levers, but the opening of the same. To close
the levers, the connecting links c c¹, or the projections of the same respectively,
are put under the action of springs d, one end of which bears against said projections,
whereas the other end bears against an adjusting screw (Fig. 2). The latter
serves also for holding one end of a rod k, the other end of which passes through
a hole in the respective projection ².
In the modified form of construction represented in Figures 3 and 4, the helical
springs of Figure 2 are replaced by spiral springs, which are held by the upper
ends of the pivots 2 and which bear against special pins d³ screwed into the lever
arms b. In all other respects the form of construction shown in Figures 3 and 4
is similar to that shown in Figures 1 and 2, except the bevel-wheel g of Figure 1
being replaced by an ordinary cog-wheel g', Figure 3, and the disk C of Figure 1
forming a cog-wheel C₁ (Figure 4). The mean for rotating the cog-wheels g¹

page_text: and C¹ may, of course, vary in a wide degree, as is also the case with the means
for rotating the shafts g³ and go, which will more fully be referred to hereinafter.
The box D) (Fig. 3) which moves the mut a (Fig. 6) over the threaded portion
of the screw-tap A, is provided with a collar k¹, against which bears a spiral
spring f. The latter supports a sleeve f, which is so connected with the box D,
that it cannot be turned around the same. A rotation of the sleeve f will thus
cause a rotation of the box D, but a longitudinal movement of the sleeve will
cause a similar movement of the box D only, if the resistance which the latter
finds in moving the nut over the threaded portion of the screw-tap, is smaller
than the strength of the spring f¹. If that resistance is greater, the box D will be
displaced but little or not at all, and the spring fl will consequently be more or
less put under compression.
The parts afore described are located in a casing F (Fig. 6), which is connected
with a bevel-wheel g (Fig. 1) by means of a piece of tube or hollow shaft ². The
bevel-wheel is secured to the outer surface of said part g2, and the casing Fis
secured to the inner surface of the same. The casing F is connected with the
sleeve by ledges or feathers f³ (Fig. 5) which take into corresponding recesses
or grooves f3 (Fig. 9). I prefer to let these grooves and the feathers have an
inclined position, so that said parts resemble parts of a screw with a very high
pitch.
The bevel-wheel g gears with a bevel-wheel g keyed to a shaft g³. The bearings
for the latter form parts of the frame of the machine, and said frame carries above
the horizontal shaft g' a vertical shaft g5, to which is secured the disk C (Fig. 2)
or C¹ (Fig. 4) afore described.
Whilst the box D turns on its axis, it is continually moved up and down by
the action of a ring s upon the sleeve f, or upon the ledges f of the same. Said
ring has as many inclined portions as there are ledges upon the sleeve f, and
is secured to the plate h, which its turn is secured to the cylinder w, that serves
as a bearing for the piece of tube or hollow shaft g³.
.
The box D is supported in the casing F by means of a vertical spring d', the
lower end of which rests upon an inner flange of the casing F, and the upper end
of which presses either against the sleeve f (Fig. 1), or against the collar kl
(Figure 3) of the box D. The compression of the spring d' is, of course, increased,
when the sleeve f descends under the action of the inclined surfaces of the ring s,
but this increase in compression does not influence the compression of the helical
spring f, that is located between the sleeve f and the collar ³.
The nut to be threaded is shoved upon the projecting upper end of the screw
tap A and is placed upon the closed arms 6 of the upper pair of levers. These
arms then open, and the nut glides down along the screw-tap, until it is stopped
by the lower arms b. Thereafter the upper arms close, so as to grasp the screw-
tap, and the lower arms open, so as to let the nut glide further down upon the screw-
tap, until it arrives at the threaded portion of the same. The nut has then also
arrived at or in the upper part of the box D. In order to enable the latter to turn
the nut upon the screw-tap, or upon the threaded portion of the same, it is
provided with as many grooves or ribs, as there are longitudinal edges on the nuts;
in other words, the section of the bore of the box D is not cylindrical, but cornered,
or, preferably, undulated, as represented in Figure 8. I prefer, to let the ribs or
grooves have an inclined position, so that they represent parts of a screw, with a
very high pitch (see Figures 5 and 6), and I further prefer to provide the upper
half of each rib of the box with notches a2 (Figure 7) of such a configuration,
that the remaining parts represent ratchet-teeth capable of preventing the nut
from moving in an upward direction relatively to the box D.
As soon as the nut has come within the reach of the upper part of the rotating
box D, the latter is moved in a downward direction by the action of the ring s
upon the ledges f² of the sleeve f. This movement is transmitted to the box D
by means of the spring f¹, and, owing to the action of the recessed ribs of the box,

page_text: the nut a is pressed against the commencement of the threaded portion of the
screw-tap A, and the threading of the nut is thus commenced.
The nut is thus first put under the pressure of the sleeve f, and as the friction
between the nut and the screw-tap increases, the spring f¹ is compressed and the
nut is thereby put under the tension of the spring, so that the downward move-
ment of the box D is shorter, than that of the sleeve f. When the nut has been
perfectly turned or screwed upon the screw-tap A, the resistance between it and the
box decreases, which finally occurs in such a degree, that the box D and the
sleeve fare raised into their normal height by means of the spring d¹, which prior
thereto had been compressed. The position of the sleeve / with regard to the
ring s is at that time such, that the ledges f are no longer acted upon by said ring.
As soon as the box D has regained its former or original position, it receives
another nut, which prior thereto had been put upon the screw-tap A, and had made
its way through between the pairs of lever-arms b. The first nut is at that time
located near to the end of the threaded portion of the screw-tap A, and owing to
the downward pressure, which the box D is subjected to under the action of the
rings upon the sleeve f, the movement of the respective nut a over the end-part
of the screw-tap is accelerated. This acceleration occurs, whilst the subsequent
nut is pressed by the ratchet-teeth a² of the box D against the commencement
of the threaded portion of the tap A, and there are thus during that time two
nuts acted upon by said box. Of course, the second nut need not be brought in
contact with this threaded portion of the tap, until the first nut has completely left
the latter, and I wish it to be understood that my improved nut-threading machine
may well be used in one way or the other.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. In a machine for threading or tapping screw-nuts, the combination with a
rotary box, a screw-tap extending into said box, and means for holding said screw-
a sleeve located between
tap, of a rotary casing enclosing said box and
the casing and the box, said sleeve being adapted to transmit rotary
motion from the casing to the box while allowing a longitudinal dis-
placement of itself as well as of said box: a stationary ring adapted
to displace the sleeve; a spring adapted to transmit the displacement of
the sleeve to the box; another spring adapted to support the box in the casing,
and means for turning the latter, substantially as described.
2. In a machine for threading or tapping screw-nuts, the combination with
a rotary box, a screw-tap extending into said box, and means for holding said
Ecrew-tap, of a rotary casing enclosing said box and a sleeve located between the
box and the casing: grooves provided in the casing opposite to the sleeve, feathers
forming part of the sleeve and projecting into said grooves, a stationary ring
located above said feathers and adapted to displace the sleeve, the latter being
adapted to transmit its rotary movement to the box while allowing a longitudinal
displacement of the latter, said feathers and grooves having an inclined position,
so as to form parts of steep screw threads; a spring or springs adapted to press
said feathers against the stationary ring; and means for turning the said casing,
substantially as described.
3.. In a machine for threading or tapping screw-nuts, the combination with a
rotary box, a screw-tap extending into said box, and means for holding said screw
tap, of a rotary casing enclosing said box and adapted to transmit rotary movement
to the box while allowing a longitudinal displacement of the same, the section of
the bore of said box being such as to enable the latter to catch and turn a nut
located upon the screw-tap, the ribs located in the bore having incisions forming
ratchet teeth between them, substantially as described.
4. In a machine for threading or tapping screw-nuts, a mounting device for
the screw-tap, consisting of the combination with at least two pairs of levers

page_text: arranged one above the other, and adapted to grasp the screw-tap, of means for
actuating said pairs alternately, so as to open one pair only when the other is
closed, substantially as described.
5. In a machine for threading or tapping screw nuts, a mounting device for
the screw-tap, consisting of the combination with at least two pairs of levers
arranged one above the other and adapted to grasp the screw-tap, of links con-
necting the two levers of each pair, and means for actuating said links alternately
so as to simultaneously open the levers of one pair after the levers of the other
pair have been simultaneously closed, substantially as described.
6. In a machine for threading or tapping screw-nuts, a mounting device for the
screw-tap, consisting of the combination with at least two pairs of levers arranged
one above the other and adapted to grasp the screw-tap, of a rotary disc located
in a plane between said pairs of levers, and projections arranged upon said disk
so as to open one pair of levers only when the other pair has been closed, sub-
stantially as described.
7. In a machine for threading or tapping screw-nuts, a
mounting device for
the screw-tap, consisting of the combination with at least two pairs of levers
arranged one above the other and adapted to grasp the screw-tap, of links con-
necting the two levers of each pair, projections forming parts of said links, a
rotary disc located in a plane between said pairs of levers, and projections
arranged upon said disc and adapted to act upon the projections of said links,
substantially as described.
Dated this 1st day of October 1898.
FAIRFAX & WETTER,
Agents, 37 and 39, Essex Street, Strand, London.