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Патент USA US2135067

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Nov. 1, 1938.
A. F. BRElTENsTElN
2,135,067
AUTOMATIC RELEASING THREAD CUTTING TOÓL
Filed Aug. 25, 1957
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Nov. 1, 193s.
2,135,067
A. F. BRElTENSTElN
AUTOMATIC RELEASING THREAD CUTTÍNG TOOL
Filed Aug. 25, 1937
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5 Sheets-sheet 2
2,135,061?
Patented Nov. 1, 1938
PATENT @FFME
, _urNi'r se Sfmt
2,135,067~
i
AUTOMATIC-RELE-A‘SIN-GS THREAD-GUT
TéING TOOL
Albert- F; Breitenstein; New- Haven,> Conn., as
signor to The Geometric ToolE Company; New>
Haven, Conn., a-corporationrofä Connecticutß '
Application. August 25,~y 1937, Seriali-No. 160,749?
8 Claims.
(Cl. 10-95)
This invention relatesl to anrimprovement in.
automatic-releasing thread-cuttingtools,4 that` is
to say, thread-cutting tools- which automatically
retire their threadrcutting. chasers from engage
ment with the work-,to thus permit the ready- and
rapid axial separation ofi` the work and tool.
More particularly, the present inventionrelatesl
to thread-cutting tools of the character referred.
to, which are employed for cutting pipe-threads
mÈv andother similarly-tapered_Ythreads,` and which
rely upon normally-stationary thread-cutting
chasers which have their series of thread-cutting
teeth arrangedat the desired angle in contra
being shown inithepositions-which they assume
distinction to thread-cutting toolsAk whichv pro
y .~, gressively retire their chasers during vthe normal
' thread-cutting operation, in order to effect the.
positions- which they. assume at the instant the
desired taper'.
.
fon a normal-vthread-cutting` operation;
Fig. LLisa sectional viewfcorresponding'to Fig.'
3; butl less comprehensivethan the same, and
showing theparts in-the positions- which they
assume; after they completeY retirement of.- the
chasers;
Fig. 5 is a fragmentary sectional'view on an
enlarged scale showingisome of the parts of the
mechanismillustrated in-vthe upper portion of
Fig. 3;
Fig. 6 is ali-fragmentarysectional view corre
spondingato Fig.` 5;.but showing thei’parts'- infthe
latch-member has been shifted.` sufficientlyv to .l
start they brief progressive> retirement of the
chasers;V
Thread-cutting‘tools ofthe type to `which the
present invention relates are. apt to leaveïoneï or
„0._more objectionable longitudinal shoulders upon
the threaded portion of' the work (especially
.
f
,
Fig.. 7 is a fragmentary sectionalview taken
onthe-line 1-1 of Fig. 2;
Fig;4 8;,is. a- similar view‘taken ontheY line -8---8` 20
of. Fig. 2;»
'
'
Fig.l 9 isa transversefsectional View taken ony
the tapered chasers» have.` been retired. radially the line 9--9ry of Fig.- 3;
Fig. 10.is a perspective viewfof thelatch-mem
from the work, much in the manner illustrated ~
in: Figs. 13 and .14 of the accompanying‘drawings. ber ofthe structure of Figs.' l to 9 inclusive;
Fig. l1Y is a viewy in side elevation of anfauto
The problem oi overcoming the diñìculty just
referredto has. longY vexed: thoser skilled inthe matic v collapsing tap'> embodying. the present in
vention;
art.
Fig. 12 isa view thereof in >central `longitudinal
The main'object, therefore», of thepresent in.-V
upon resilient material such as- soft brass) after '
„0 „ ventionis to provideza superior automatic-'releas
Fig. 13- Ais-a schematic sectional view showingA
ing die-headfin cutting tapered threadsupon the
cutting tool which‘will» maintain its-thread‘fcut
the work shownffin Fig.l 13; '
ting chasers in ’rixed'radialV position during the
normal threading operation, and> which- will at“
the termination of` such operation retire the
40 chasers radially in such manner as to erase orl
substantially erase such. longitudinal shoulders
as may exist upon the work at that time.
With theabove and other objects in View, as
_A will appear to those skilled in the art from the
or. U ‘present disclosure,` this invention includes all_`ieatures in the said disclosure which are novel over
the prior art. ¿
_
section;
ing thread-cutting tool» of the type referredßto;
which will produceA tapered'threads free from‘
abruptlongitudinal shoulders.
A further object of the present invention is'
to provide a superiorautomatic-releasing thread
the action of one`of lthe chasers .of .the self-open
work and the resultant longitudinal> shoulder
upon-the latter; '
Fig. .14 isa broken.- face View ofv a section of
35
Fig. 15 is a-transverse sectional View through
thefwork‘, `showing the erasure vof. the longitudinal
shoulder appearing in Fig'. 13, bythe novel action'r
of the self-opening dieehead structure of‘Figs. 1`
to 10 inclusive;VV
Fig.-~ 16'is fa.; fragmentary'perspective View of
the Chaser-operating"sleeve; and`
Eig.' 1'7_ isian enlarged fragmentary View of the
let-oli. shoulder.v ande. cooperatingl parts of . the
structure shown’inr Fig. 12';
`
Thev automatic-‘releasing or self-'opening die
_
In vthe accompanying drawings:
.
Fig.Y l is a-viewlin side elevation of one` for
which a self-opening die-head` embodying the
present invention may assume;
30
‘
Y
_
Fig. 2is iront face viewîthereof;
Fig. 3‘ is, a View* thereof in central longitudinal `
head. herein-chosen» for the illustration of- the
present’inventionf in Figs.. lv toy l0«~inclusive» com 50.
prises a= body-member, generally designatedby
the referenceA character 2li.,` having atf‘its forward
end»anenlargedheadàportion 2 Iland provided at
its .rearend withz.azh'ol1ow shank 22'.Y The. said'
555'section takenfon. the liner-'3,-3fof Fig.;2, theparts. headeportio‘n _2 I .risformed in' its` forward face with
2 Y
2,135,067
four (more or less) equidistant radial slots 23,
in each of which is mounted a radially-movable
chaser 24.
The inner edge of each of the chasers 24, just
referred to, is formed with a series of thread
inclination of about 81/2" with respect toI the
plane of the latching-shoulder 351)I of the latch
member 34, but in any event, the said let-off
shoulder must have a non-camming angle-rela
tionship of substantially less than 45"l with re
cutting teeth 25 tapering forwardly and out-V spect to the plane of the latching-shoulder which
wardly at an angle substantially corresponding it intersects, so that the said let-off shoulder
to the desired angle of the threads to be cut cannot act-as a cam-surface and thus enable the
upon the work. For purposes of clarity of illus
Chaser-operating sleeve 30 (acting under the urge
tration, the taper of each series of thread-cut- , of the springs 3`|-3'|) to force the latch-mem 10Y
ting teeth 25, just referred to, has been exag
ber 34 inwardly into its retired position. If the
gerated over and above the taper customary >in latter action were to be permitted, the let-oil“
pipe-threads.
shoulder 35a would cease to function as such, and
The chasers 24 are retained in place'in the slots the chasers would be retired substantially in
23 in the head-portion 2| of the body-member stantaneously, thus leaving marks or ridges up
2D by means of segmental plates 26 which are se
on the work.
cured to the said head-portion` by screws 2l.
To provide for disengaging the latch-mem
Each Chaser is formed at its outer’end with a ber 34 from the latching-shoulder 36 in the
sloping cam-surface 28 which is engaged by a ‘ Chaser-operating sleeve 30, by means of an ex
20 similarly-sloping cam-surface 29, one of which ternal abutment to permit the rearward retire
20
latter is formed upon the inner forward corner ment of the said sleeve under the urge of its
of a Ysubstantially-cup-shaped Chaser-operating springs 31-31, a tripping-sleeve 4| is employed
sleeve 30`adjacent each of the said chasers. ’I'he which is' mounted upon the Chaser-operating
said Chaser-operating sleeve is mounted upon the sleeve 30 with capacity for axial movement there
25 body-member 20 with capacity for axial sliding on. The said tripping-sleeve 4| is provided with
25
movement thereon, and bears at its forward end an> internal cam-surface 42 which, when the
upon the periphery of the head-portion 2| of the sleeve is moved rearwardly, is adapted to exert
body-member, and at its rear end bears upon inward pressure upon a ball 43 which is movable
the periphery of a latch-carrying ring 3| mounted radially in a radial guide-passage 44 formed in
30 upon the said body-member with capacity for the rear portion of the Chaser-operating sleeve
30
axial adjustment thereon. The axial adjust
3|). The said ball 43 is adapted to bear upon the
ment of the latch-carrying ring 3|, just referred periphery of the latch-member 34 for the pur
to, is effected by an adjusting-nut 32 threaded pose of urging the latter inwardly, as will here
upon the body-member 20 just forwardly of the
35 shank 22 thereof.
The latch-carrying ring 3|, above referred to,
is >formed with a transverse notch 33 provided
for the reception and guidance of a substantially
semicircular latch-member 34, the outer pe
40 riphery of which corresponds in curvature to the
curvature of the outer periphery of the latch
carrying ring 3|, above referred to. The forward
face of the latch-member 34 constitutes a latch
ing-abutment Vgenerally designated by the refer
character 35 and is adapted to- vengage with
45 ,ence
a substantially-semicircular latching-abutment
-
Save for the let-off shoulder 35a, in particular, 35
the die-head organization above described may
be said to be old in the art and it has been set
forth and described herein for the purpose of
enabling the operation of the let-oí shoulder
or its equivalent to be properly understood.
40
For'purposes of description, Vlet it be presumed
that the die-head structure is mounted by means
of its shank 22 in the rotating chuck of a thread
cutting machine and that it is advanced axially
toward the work 45 for the purpose of cutting
a pipe-thread thereon.
.
36 curved lengthwise of itself and formed in the
interior of the Chaser-operating sleeve> 30 for the
After the die-head has been threaded onto the
work as above described to the desired extent,
« purpose of releasably holding the said sleeve in
the tripping-sleeve 4| will have been arrested,
by any suitable stop, against further forward
its forward chaser-closing position against the
50 rearward urge of a pair of retracting-springs
31-31 (Figs. 8 and 9). The said retracting
springs are respectively located at diametrically
opposite points in the die-head structure, as
55 Vshown in Fig. 9, and have theirrforward ends
seated in sockets 38 opening rearwardly through
the head-portion> 2| of lthe body-member> 20.
The rear end of each of the said retracting
springs is seated in a socket 39 opening forward
60
inafter appear.
ly from the adjacent contracted portion of the
Chaser-operating sleeve 3B.
To pro-vide for the erasure of longitudinal
shoulders which might otherwise be left upon
the work by the chasers, the outer forward corner
of
the latch-member 34 is cut away to provide
65
an outwardly-and-rearwardly-inclined let-off
shoulder 35a which extends from a radially-ex
tending latching-shoulder 35h of the said latch
member 34 to the outer periphery thereof. The
70 said let-oli shoulder is.most clearly shown in
Figs. 5, 6 and 10 of the accompanying drawings
and, together with the latching-shoulder 35h,
constitutes part of the latching-abutment 35. In
the particular type of structure shown in the said
75 ñgures, the let-olf shoulder 35a preferably has an
45
movement with thedie-head structure so as to 50
cause’ its cam-surface 42 to act through the ball
43 to move the latch-member 34 inwardly into
the position in which it is shown in Fig. 6, thus
bringing the sloping let-off shoulder 35a of the
said latch-member into position for coaction with
the lower edge of the latching-abutment 36 in
the Chaser-operating sleeve 3i). The chasers 24
will now be in progress of cutting the threads
upon the work 45 and each will be producing a
longitudinal’shoulder 46 (Figs. 13 and 14) upon 60
the threaded portion of the work 45. If at this
time the chasers were to- be instantly released
from the work, as is the> ordinary practice, the
shoulders` 46 or their equivalent would remain 65
visible upon the threaded portion of the work
45. Instead, however, of abruptly retiring the
chasers out of engagement with the work, the
let-01T shoulder 35a upon the latch-member 34
will now come into action and, though operating
within a very Vshort period of time, will now cause
the said chasers to retire slowly for a short dis
tance to thus “erase,” so to speak, the longitu
dinal shoulders 46 from the threaded portion of
the work, as may be seen by comparing Fig. 13 75
with Fig. 15 of the accompanying drawings. As
soon as-the outer edge of the let-olf shoulder 35a.
clears the inner edge ofthe latching-abutment
35, the Chaser-operating sleeve-30 will be snapped
rearwardly by its retracting-springs 31 into the
position in which it is shown in Fig. 4, thereby
permitting the individual retracting-springs 41
permit the inward` retirement of the chasers 54,`
of the chasers 213 to force the said chasers radial
thesaid latch-member is formed in its forward
ly outwardly completely clear of thework so that
10 the die-head structure andthe work may be`
axially separated preparatory to another thread
ing operation.
.
In Figs. 11 and 12 is shown a so-called “col
lapsing tap” structure incorporating the novel
let-off feature of the present invention. The c_ol
lapsing tap referred to includes a cylindrical
body-member 5|) having an axial bore 5| for the
reception of a Chaser-operating plunger 52 which
reciprocates therein. The forward end of the
20 said VChaser-operating plunger is tapered and
formed with Chaser-actuating ribs 53 ñtting into
corresponding grooves in the inner ends of a set
of thread-cutting chasers' 54, each ofY which- is
formed in its outer edge with a sloping’series
The chasers 54 are
25 of thread-cutting teeth 55.
mounted in radial grooves 55 formed in the for
ward end of the body member 5&1 and are nor
mally held in place against forward displacement
by a cap 51 secured to the forward end of the
30 said body-member 55.
Mounted upon the forward portion of the body
member 55,;with capacity for axial sliding move
ment thereon, is a latch-carrying sleeve 58 which
in turn has mounted upon it, also with capacity
35 for axial movement, atripping-sleeve 59. The
rear portion of the tripping-sleeve 59 bears upon
the periphery of an annular ñange Bü which
forwardly projects from an adjusting-ring 5|,
which latter is provided with internal threads 52
40 for engagement with external threads 63 formed
upon the periphery of the body-member 59.
Adjacent its rear end, the Chaser-operating
plunger 52 is formed with an elongated diametri
cal passage 64 through ¿which extends a coupling-v
45 bar 55 which extends through a clearance-slot
BB formed in the adjacent portion of the body
member 5B and into coupled relationship with
the latch-carrying sleeve 58, before described.
The said coupling-bar 65 thus serves to couple
50 the latch-carrying sleeve 58 with the chaser
operating plunger 52 for concurrent axial move
ment with respect to the collapsing-tap struc
ture.
Projecting rearwardly from the chaser-operat
55 ing plunger 52 is a bolt 61 having at its rear`
end a kerfed head 68, the under face of which
latter forms a forwardly-facing spring-seat for
engagement by the forward end of a helical re
tracting-spring 69 which encircles the rear por
60 tion of the bolt 61 and bears at its forward end
against a washer-like spring-seat 1|! through
which the said bolt 61 extends, as is clearly shown
in Fig. 12.
The latch-carrying sleeve 58 is formed with
65 a notch 1| which receives and guides a radially
movable semicircular ring-shaped latch-member
12, the rear face of which constitutes a latching
abutment similar to the latching-abutment 35
of the self-opening die-head before described, and
70 which is adapted to engage with a latching
Vabutment 14 constituting the forward face of
the flange 55 of the adjusting-ring 5|, before de
scribed. Idke the latching-abutment 35 of the
latching-member 12-V now under discussion,` is
formed with a radially-extending latching-shoul
der 15a and a sloping let-off shoulder 15b which
joins the; latching-shoulder 15a, with the outer
surface of the latch-member 12. To effect the 5;
inward movement of the latch-member 12 to
outer corner with a cam-surface 16 which is
engaged by a `similarly-sloped cam-surface 11
formed in the interior of the tripping-sleeve 58.
`For the purpose of manually moving the trip
ping-sleeve »59 rearwardly to effect the manual
tripping ofthe `tap or for moving the said trip
ping-sleeve forwardly, to cause the same in turn
to similarly-_move the'latch-carrying sleeve 58,
to reset the chasers 54 in. their projected or op
erative positions, a lever-handle 18 is employed.
The saidlever-handle is mounted in the tripping
sleeve 59 upon a> transverse pin 19, which lat
ter extendsdiametrically through a spherically
contoured boss 80 on the said handle. The said
spherically-contoured boss 80 ñts within a pas
sage 8|; in the `said sleeve 59 and serves to ex
clude chips .and- dirt from the interior of the die 25'
head` structure._ VThe inner end of the lever
handle 'I8 projects inwardly through a clearance
passage 82 formedV in the latch-carrying sleeve 5B
and is provided with a spherically-contoured ter
minal` 83 fitting into a socket 84 formed in the
body-member 50, before referred to.
Inlorief,A the operation of the collapsing tap
illustrated'in` Figs. 11 and 12 is as follows:
Assuming that the parts are in the positions
inV which> they are> shown in the drawings, the 35
tap will be _moved toward the work or the work
towardthe tap so as to cause the now-projected
chasers 54` to enter the work. vWhen the work
has been threaded to `the desired extent, the tap
may be tripped for retiring the chasers 54 in- .if
wardly completelyout of engagement with the
work either by an abutment acting to move the
tripping-sleeve 5S rearwardly with respect to the
die-head structure or by the manual rearward
movement ‘ofA the vupper end of the lever-handle
1.8.. When thetripping-sleeve 59 is moved rear
wardly as described, its cam-surface 15 will act
upon. the cam-surface 11. of the latch-member 12
and. force the latter inwardly. Shortly after the
starting of; the inward movement of the latch- .
member 12 its radially-extending latching-shoul
der 15a will lride-clear of the inner corner of the
l'atching-abutment 14` and the sloping let-off
shoulder 15bIwil1 now` ride against the inner cor
ner 'or edge of thefsaid abutment 14and for a
brief: interval of time, ‘thus gradually retire the
chasers 54Í under the urge of the spring SS act
ing through the Chaser-operating memberV 52.
As soon as the outer end of the let-off shoulder
15b has clearedthe inner edge of the latching
abutment 14,*the latch-carrying ksleeve and hence
ther Chaser-operating plunger 52 will be moved
quickly to; the'lrearA to thusv effect the complete
retirement of the chasers 54 so that the die-head
structure andthe now-threaded Vwork may be 65
axially separated preparatory to another thread
-ing operation.
’
‘
>
`
„The 1er-off shomder 15b of the structure ofl
Figs. 411 and` 12 functions in substantially the
same manner vas the let-off shoulder 35a of the
structure of Figs. 1 to ll() inclusiveV and will serve
to cause Vthe erasure> or substantial erasure of
latching-member 34, before described, the latch
longitudinal lines or shoulders which might
otherwise be left inthe threaded portion of the
ing-abutment formed by the rear face of. the
work, `îwerepthe chasers 54 to bek fully retired 75..
4
without the intervention of the said let-‘oif?shoul
ried by the said body-unit; spring-means urging
der 15b.
the said chasers into their retired or inoperative
a latch-releasing member; and a
latch-member releasable by the said latch-releas
ing member and releasably holding the said
chasers in their advanced or thread-cutting posi
tions, the said latch-member being provided with
l
Y
The invention may be carried out invother spe
ciñc ways than those herein set forthV without
departing from the spirit and essential char
acteristics of the invention, and the present em
bodiments are, therefore, to be considered in all_
respects as illustrative and not restrictive, and all
changes coming within the meaning andequìv
10 alency range of the appended claims are in
tended to be embraced therein.
I claim:
positions;
a latching-abutment comprising a latching shoul
der arranged to engage with the latching-abut
ment of the said body-unit to iixedly but releasably 10
hold the said chasers in their advanced or'
`
"
1. An automatic-releasing thread-cutting tool,
comprising: a body-unit having a latching-abut
15 ment; a plurality of substantially-radially retir
able and advanceable thread-cutting chasers
carried by the said body-unit; spring-means urg
ing the said chasers into their retired or inopera
tive positions; a latch-releasing member; and a
20' latch-member movable into releasing position by
the said latch-releasing member and releasably
holding the said chasers in their advanced or
thread-cutting positions, and ,a let-off shoulder
intersecting the said latching-shoulder at a non
camming angle of substantially less than 45° with
respect to the plane thereof and operatively en 15
gaging the latching-abutment of the said body
unit after the said latching-shoulder has been
moved out of operative engagement with the
same to subsequently cause the progressive re
tirement of the said chasers to substantially erase
longitudinal shoulders left upon the Work by the
said chasers.
4. An automatic-releasing thread-cutting tool,
thread-cutting positions, the said latch-member
being provided with a latching-abutment 'position
comprising: a body-unit having a latching-abut
25 ed to engage with the latching-abutment of theY ment curved lengthwise of itself; a plurality of 2'5
substantially-radially retirable and advanceable
saidbody-unit; one of the aforesaid latching-abut
thread-cutting chasers carried by the said body
inents comprising a latching-shoulder and a let
unit; spring-means urging the said chasers into
ofi shoulder intersecting the said latching-shoul
their retired or inoperative positions; a latch
der and inclined with respect to the plane there
of at a non-camming angle of substantially less
than 45°, the said latching-shoulder being posi
tioned to fixedly restrain the said chasers in their
advanced or thread-cutting positions during the
normal thread-cutting operation of the tool and
the said let-off shoulder being positioned and
inclined to cause the progressive retirement of
the said chasers at the termination of the nor
mal thread-cutting operation to substantially
erase longitudinal shoulders left upon`the work
40
by the said chasers'.
.
'
’
2. An automatic-releasing thread-'cutting tool,
comprising: a body-unit having latching-abut
ment curvedlengthwise of itself; a plurality of
substantially-radially retirable and advanceable
45 thread-cutting chasers-carried by the said body
unit; spring-means urging the said chasers into
their retired or inoperative positions; a latch
releasing member; and a latch-member curved
lengthwise of itself and movable into releasing
50
position by the said latch-releasing member and
releasably holding the said chasers in their ad
vanced or thread-cutting positions, the said
latch-member being provided with a latching
releasing member; and a latch-member curved
lengthwise of itself and releasable by the said
latch-releasing member and releasably holding
the said chasers in their advanced or thread
cutting positions, the said latch-member being
provided
with
a
latching-abutment
curved
lengthwise of itself and'comprising a latching
shoulder curved lengthwise of Yitself and arranged
to engage with the latching-abutment of the said
body-unit to ñxedly but releasably hold the said
chasers in their advanced or thread-cutting posi
tions, and a let-off shoulder curved lengthwise of
itself and intersecting the said latching-shoulder
at a non-camming angle of substantially less
than 45° with respect to the plane thereof and
operativelyV engaging the latching-abutment ofthesaid body-unit after the said latching-shoul
der has been moved out of operative engagement
with the same to subsequently cause the progres
sive retirement of the said chasers to substan
tially erase longitudinal shoulders left upon the
work by the said chasers.
'
50
5. A self-opening die-head, comprising: a body
unit having a latching-abutment; a plurality of
substantially-radially retirable and advanceable
thread-cutting chasers carried by the said body
the said body-unit; one of the aforesaid latching- ' unit; spring-means urging the said chasers out
abutments comprising a latching-shoulder curved wardly into-their inoperative positions; a latch
lengthwise of itself and a let-off shoulder curved releasing member; and a latch-member movable
lengthwise of itself and intersecting the said into its releasing position by the said latch-re
60 latching-shoulder and inclined with respect- to leasing member and releasably holding the said 60
the plane thereof at a non-cammingangle of chasers in their inwardly-projected thread-cut
substantially less than 45°,the said latching-> ting positions, the said latch-member being pro
abutment curved lengthwise of itself and posi- '
tioned to engage with the latching-abutment of
65
shoulder being positioned to ñxedly restrain the
vided with a latching-abutment positioned to en
said chasers in their advanced or thread-cutting
gage with the latching-abutment of the said body
positions during the normal thread-cutting op-A unit; one of the aforesaid latching-abutments ce
eration of the tool and the said let-off shoulder‘ comprising a latching-shoulder and a let-off _
being positioned and inclined to cause the pro? shoulder intersecting the _said latching-shoulder
gressive retirement of theV said Vchasers at the ter
and inclined with respect to the plane thereof at
mination of the normal thread-cutting operation ’ a non-camming angle of substantially less than
to substantially erase longitudinal shoulders leftV 45°, thek said latching-shoulder being positioned 70
upon the work by the said chasers.
to fiXedly restrain the said> chasers in their in
3. An automatic-releasing thread-cutting tool, `
comprising: a body-'unit having a latching-abut
ment; a plurality of substantially-radially retir
wardly-projected thread-cutting positions during
the normal thread-cutting operation of the die
head and the said let-off shoulder being posi
75 jable and advanceable thread-cutting chasers car- ' tioned and inclined to cause the progressive re 75
2,135,067
tirement of the said chasers at the termination
of the normal thread-cutting operation to sub
stantially erase longitudinal shoulders left upon
said latch-member being provided with a latch
ing-abutment comprising a latching-shoulder ar
ranged to engage with the latching-abutment of
the work by the said chasers.
6. A self-opening die-head, comprising: a body
the said body-unit to ñxedly but releasably hold
the said chasers in their advanced or thread
unit having a latching-abutment curved length
wise of itself; a plurality of substantially-radially
retirable and advanceable thread-cutting chasers
cutting positions, and a let-oiî shoulder intersect
ing the said latc‘ning-shoulder at a non-camming
angle oi substantially less than 45° `with respect
to the plane thereof and operatively engaging the
latching-abutment of the said body-unit after the 10
Ycarried by the said body-unit; spring-means urg
ing the said chasers outwardly into their inop
erative positions; a latch-releasing member; and
erative engagement with the same to subsequently y
movable into its releasing position by the said
latch-releasing member and releasably holding
the said chasers in their inwardly-projected
ers to substantially erase longitudinal shoulders
left upon the work by the said chasers.
15
thread-cutting positions-the said latch-member
being provided with a latching-abutment curved
lengthwise of itself and positioned to engage with
the hatching-abutment of the said body-unit;
20 one of the aforesaid latching-abutments compris
ing a latching-shoulder curved lengthwise of it
self and a» let-off shoulder curved lengthwise of
itself and intersecting the said latching-shoulder
and inclined with respect to the plane thereof at
25 a non-camming angle of substantially less than
45°, the said latching-shoulder being positioned
to ñxedly restrain the said chasers in their in
wardly-projected thread-cutting positions during
the normal thread-cutting operation of the die
30 head and the said let-off shoulder being posi
tioned and inclined to cause the progressive re
tirement of the said chasers at the termination
of the normal thread-cutting operation to sub
stantially erase longitudinal shoulders left upon
35 the work by the said chasers.
7. A collapsing tap, comprising: a body-unit
having a latching-abutment; a plurality of sub
stantially-radially retirable and advanceable
thread-cutting chasers carried by the said body
40 unit; spring-means urging the said chasers ra
dially inwardly >into their retired positions; a
latch-releasing member; and a latch-member re
leasable by the said latch-releasing member and
releasably holding the said chasers in their out
45
said latching-shoulder has been moved out of op
a latch-member curved lengthwise of itself and
wardly-projected thread-cutting positions, the
cause «the progressive retirement of the said chas
8. A collapsing tap, comprising: a body-unit
having a latching-abutment curved lengthwise of
itself; a plurality of substantially-radially retir
able and advanceable thread-cutting chasers car
ried by the said body-unit; spring-means urging 20
the said chasers radially vinwardly into their re
tired positions; a latch-releasing member; and
a latch-member curved lengthwise of itself and
releasable by the said latch-releasing member and
releasably holding the said chasers in their out 25
wardly-projected thread-cutting positions, the
said latch-member being provided with a latch
ing-abutment curved lengthwise of itself and
comprising a latching-shoulder curved length
wise ofl itself and arranged to engage with the 30
latching-abutment of the said body-unit to fìxedly
but releasably hold the said chasers in their ad
vanced or thread-cutting positions, and a let-0E
shoulder curved lengthwise of itself and inter
secting the said latching-shoulder at a non-cam 35
mlng angie of substantially less than 45° with re
spect to the plane thereof and operatively engag
ing the latching-abutment of the said body-unit y
after lthe said latching-shoulder has been moved
out of operative engagement with the same to
subsequent cause the progressive retirement of.
the said chasers to substantially erase longitudi
nal shoulders left upon the work by the said
chasers.
f
ALBERT F. BREITENSTEIN.
45
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