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Патент USA US3087176

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April 30, 1963
E. P. SUNDHOLM
3,087,174
INTERNAL THREAD ROLLING MANDREL
Filed Feb. 11. 1960
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ATTORNEYS.
United States Patent O?ice
3,087,174
Patented Apr. 30, 1963
1
2
3,087,174
completed cap in section, which shows the internal threads
I that have been formed by the threading operation. As
INTERNAL THREAD ROLLING MANDREL
Edwin P. Sundholm, Albert City, Iowa
Filed Feb. 11, 1960, Ser. No. 8,039
4 Claims. (Cl. 10-152)
explained in my copending application Serial No. 8,038,
?led February 11, 1960, entitled “Method of Forming In
ternally Threaded, Gasket-Retaining Caps,” completed
caps like the one shown in FIG. 5 of this application are
particularly adapted for use as the dispensing head caps of
cartridge-loading grease guns.
In the illustration given, the mandrel assembly M in
assembly for forming internally threaded caps.
The conventional means of forming threads on the 10 cludes a support which is built-up from a base plate 10
and an upwardly extending post 11 which has its lower
inside of a tubular member is by a thread cutting tool
end bolted to base plate 10, as indicated in FIG. 1. A
which removes metal as the threads are formed. Attempts
mandrel 12 is mounted on the support, and more speci
have been made to provide tubular members with inter
?cally on the post 11. In the illustration given, the
nal threads by rolling the tubular member against and
around a thread-forming mandrel. With tubular members 15 mandrel 12 extends into post 11 and is threadedly con
nected thereto. The ‘arrangement is such that mandrel
which have a closed end, such as caps, it has been found
12 remains in ?xed relation to post 11 and base plate 10,
to be very di?icult to remove them from the threading
although the whole assembly may rotate with base plate
mandrel after the threads have been formed. Because
10 where the base plate comprises part of a turntable
of the relatively narrow width of the cylindrical wall of
most caps, ‘it is desirable to position the cap in relation 20 providing a series of operating stations, one of which is
the thread forming station shown in FIG. 1.
to the threads on the mandrel by having the closed end of
As indicated in FIG. 1, and shown more clearly in
the cap engage the free end of the mandrel. Since the
FIGS. 2 and 3, the mandrel 12 projects outwardly from
thread forming rollers which press the side wall of the cap
the supporting post 11 and provides a free end portion
into the threading portion of the mandrel will normally
‘adapted for insertion in the open end of the cap to be
rotate around the mandrel in ‘a direction tending to tighten
threaded, such as cap C of FIG. 4. As shown in FIGS.
the cap on the mandrel as the threads are formed, the
2 and 3, this free end portion of mandrel 12 provides a
closed end of the cap will be wedged very tightly against
cylindrical band of threads 13 adjacent the outer end of
the free end of the mandrel on the completion of the
the mandrel for forming corresponding threads inside the
threading operation. Consequently, the cap cannot be
readily removed from the mandrel, and this makes the 30 cylindrical side wall a of the cap C.
In accordance with the present invention, a movable
use of internal thread rolling procedures much less attrac
shoe 14 extends outwardly beyond the outer end of
tive for the production of caps than such procedures
mandrel 12, as indicated in FIG. 1 and shown more
would otherwise be.
clearly in FIG. 2. The outer end of shoe 14 should be
It is therefore an object of the present invention to
adapted to ?rmly engage the inside surface of the closed
provide an internal thread rolling mandrel, or mandrel
end of the cap as the cap is being threaded. For exam
assembly, which provides a solution to the problem de
ple, in the illustration given, cap C provides a closed end
scribed above. More speci?cally, it is an object of the
with a substantially ?at inside surface disposed at right
present invention to provide a mandrel assembly which
angles to the axis of the cap. Similarly, the outer end
permits the cap to be positioned by clamping its closed
of shoe 14 is made substantially ?at and is disposed at
end against the free end of the mandrel during the
right angles to the axis of the mandrel 12. This permits
threading operation while at the same time permitting the
the outer end of the shoe 14 to seat ?rmly against the
cap to be readily unscrewed from the mandrel after the
This invention relates to an internal thread rolling
mandrel, or more speci?cally, to a thread rolling mandrel
inside of the cap end in the manner ‘best illustrated in
and advantages will be indicated in the following detailed 45 FIG. 2.
FIG. 2 is illustrative of the desired position of shoe 14
speci?cation.
during the threading operation. It will be noted that
This invention is shown in an illustrative embodiment
in this position shoe 14 holds the closed end of cap C
in the accompanying drawing, in which
away from the outer end of mandrel 12. This clearance
FIGURE 1 is a side elevational view, partly .in section,
of a thread rolling machine with which the mandrel as 50 is indicated at 15 in FIG. 2.
To fully accomplish the objects of the present invention,
sembly of the present invention can be employed in the
the shoe 14 should be retractable to a position closer to
production of internally threaded caps;
the outer end of mandrel 12 than the position it occupies
FIGURE 2 is an enlarged fragmentary sectional view
during the threading operation. In the illustration given,
showing the mandrel of FIG. 1 and certain related parts,
the mandrel and associated parts being shown as they 55 shoe 14 is retractable to the position illustrated in FIG.
3 where its outer end is in line with the outer end of
would appear during the threading operation;
mandrel 12. When the shoe 14 is thus withdrawn, it
FIGURE 3 is a view similar to FIG. 2 except that the
is disengaged from the cap end. The space between the
mandrel and associated parts are shown as they would
completion of the threading operation. Further objects
cap end b and the shoe 14 is indicated at 16 in FIG. 3.
appear after the completion of the threading operation
By disengaging the shoe from the cap end the cap can be
and just prior to the removal of the completed cap;
60
readily unscrewed from the mandrel after it has been
FIGURE 4 is a side sectional view of a cap prior to
threaded.
threading; and
The mandrel assembly of this invention also includes
FIGURE 5 is a view similar to FIG. 4 showing the
means within the mandrel 12 for movably supporting the
cap as it would appear after being threaded.
Looking ?rst at FIG. 1, there is shown a thread rolling 65 shoe 14, and also means for extending and retracting the
shoe. In the illustration given, the mandrel 12 is pro
machine which includes a mandrel assembly M and a
vided with a longitudinal bore 17 which extends inwardly
roller assembly R. This machine is adapted for use in
from the outer end of the mandrel. If desired, the outer
forming threads on the inside of a cap, such as the cap C
end of bore 17 may be enlarged as indicated at 18 to
shown in FIG. 4, which has a cylindrical side wall a and a
closed end b. In FIG. 1 the cap is also indicated by the 70 provide a recess for receiving shoe 14 when it is fully
retracted.
letter C and is shown as it would appear on the comple
tion of the threading operation. FIG. 5 illustrates the
A pin 19 is slidably mounted within bore 17 with
3,087,174
4
3
its outer end adjacent the free end of the mandrel 12.
12 and will thus press against the shoe 14 which is holding
With this arrangement, shoe 14 can be supported by at
1t away from the outer end of the mandrel. This arrange
taching it to the outer end of pin 19. In the illustration
ment thereby provides an alternate means for holding the
given, shoe 14 is formed integrally with pin 19. Also,
outer end of the shoe 14 in engagement with the inside
the inward face 20 of shoe 14, as indicated more clearly
surface of the closed end of the cap as the cap is being
in FIG. 2, has a conical shape which mates with the
threaded.
conical shape of recess 18. When the shoe 14 is fully
As indicated in FIG. 1, the roller assembly R includes
retracted, as shown in FIG. 3, the conical surfaces 18
a plurality of rollers 34 which are arranged circumferen
and 20 engage, and this provides a positive stop for the
tially around the projecting end portion of mandrel 12,
inward movement of shoe 14. To provide for the actua 10 the rollers being carried between an assembly 35 and a
tion of shoe 14, pin 19 extends through a bore in post 11
guide plate 36. Assembly 35 includes a hydraulic-mechani
and into a block 21 which forms a lateral extension of
cal mechanism for moving the rollers inwardly until they
post 11 and is releasably connected to post 11 by means
engage the portion of the cap wall a opposite the threaded
band 13 of the mandrel. In other words, assembly 35
of a lock nut 22, as indicated in FIG. 1.
Pin 19 is pre
vented from rotating without interfering with the required 15 and the rollers 34 rotate ‘around the mandrel 12 on an
degree of sliding movement by means of a key 23 which
axis of rotation corresponding with the axis of the mandrel.
engages a slot 24.
The individual rollers 34 are also free to rotate on their
Block 21 also provides a bore 25 which intersects the
own axes. The relative position of the rollers 34 and the
bore receiving pin 19 and is arranged at an angle thereto.
cap C during the thread rolling operation is indicated in
In the illustration given, the axis of bore 25 forms a 90° 20 FIG. 2. It will be noted that the rollers 34 press a por
angle with the axis of pin 19. The inner end of pin 19
tion of the cap wall inwardly against the threaded band
extends into bore ‘25, and is provided with an inclined
13, thereby forming corresponding threads on the inside
face 26 which is designed to function as a camming sur
of the cap. After the completion of the threading opera
face. A rod 27 is slidably received within bore 25, and
tion, the rollers 34 move outwardly to disengage the cap,
is provided with an inclined camming face 28 which en 25 and the cap is also disengaged from the holding piece
gages the face 26 of rod 19. The arrangement is such
33 after the pressure has been released within cylinder
that when rod 27 moves upwardly, as indicated in FIG.
30 to permit shoe 14 to retract slightly. For example,
2, pin 19 moves in the direction of the free end of mandrel
after the clamping engagement of the shoe 14 has been
12, and thus extends shoe 14. An adjustable stop is pro
released, plate 10 can be rotated carrying the mandrel and
vided to limit the upward movement of pin 27, which 30 cap with it and thereby separating the cap from the hold
in the illustration given comprises setscrew 29.
ing piece 33. This position is indicated in FIG. 3. The
An air cylinder 30 is mounted on base 10, as shown
in FIG. 1. A downward extension of block 21 connects
with the upper end of air cylinder 30, and rod 27 ex
tends within the cylinder where it is connected to a mov
able piston 31. A compressed air inlet 32 is provided
cap can now be readily removed from the mandrel by
unscrewing it manually or by a simple mechanical device.
The completed cap after removal from the mandrel is
shown in FIG. 5.
Where a holding piece 33 is employed as described
above, and the holding piece is supported within the rotor
beneath piston 31 so that when compressed air is applied
to cylinder 30 piston 31 will move upwardly carrying
assembly R, the holding piece should be rotatably mounted
rod 27 with it until the upper end of the rod strikes set
so that it can remain stationary while the assembly R
screw 29, or until shoe 14 has clampingly engaged the
rotates about the mandrel 12. In other words, during
closed end b of the cap C. Normally, screw 29 will be
the thread rolling operation where the cap is clamped
positioned so that its lower end will just engage the top
between the end of the holding piece 33 and the outer
of rod 27 when shoe 14 is in its extended, or cap engaging
end of shoe 14, holding piece 33 will remain stationary
position, as indicated most clearly in FIG. 2.
except when the cap C rotates on the mandrel. Some
With the arrangement just described, as long as piston 45 rotation of the cap during the threading operation can
31 is held in its elevated position by the air pressure
be expected.
within cylinder 30, shoe 14 will hold cap C away from
The rollers 34 will normally rotate around mandrel 12
the outer end of mandrel 12.
As soon as the pressure
and cap C in a direction tending to tighten the cap on
is released within cylinder 30, however, piston 31 will drop
the mandrel during the threading operation. This action
down bringing rod 27 with it, and releasing the force 50 is much as if the cap was already provided with threads
applied to pin 19. This action causes shoe 14 to release
and was being run onto the mandrel. The preferred direc
its engagement with cap C, this position of the movable
tion of rotation, of course, will depend on whether the
elements being shown in FIG. 3. It should be kept in
threads are left-handed or right-handed. When right
mind that only a very small movement of the shoe 14 is
handed threads are being applied to the cap, the rollers
55
required to accomplish the desired results. For example,
will rotate clockwise when viewed in the direction of the
a movement of ten to twenty thousandths of an inch will
free end of the mandrel.
usually be su?icient.
Preferably there is also provided a holding piece 33
supported within roller assembly R, as indicated in FIG.
While in the foregoing speci?cation this invention has
been described in relation to a speci?c embodiment thereof
and many details have been set forth for purpose of illus
1, and having an outer end adapted to engage the outer 60 tration, it will be apparent to those skilled in the art
surface of the closed end of cap C. The desired relation
that the invention is susceptible to other embodiments
ship of these parts while the threads are being formed is
and that many of the details described herein can be
shown in FIG. 2. It will be noted that the end b of the
omitted or varied without departing from the basic prin
cap C is securely clamped between holding piece 33 and
ciples of the invention.
shoe 14, and that the holding piece and shoe are dimen 65
I claim:
sioned to engage a major portion of the diameter of said
1. A mandrel and roller assembly for use in forming
cap. If desired, holding piece 33 can be backed by a
threads on the inside of ‘a metal cap having a cylindrical
spring.
side wall and one closed end, comprising a support, a
Holding piece 33, while desirable, is not absolutely
mandrel ?xedly mounted on said support, said mandrel
essential. The upward movement of rod 27 and thereby 70 projecting outwardly from said support and providing a
the outward movement of pin 19 and shoe 14 can be
free end portion adapted for insertion in the open end
limited by means of setscrew 29. Shoe 14 will then en
gage the inside of cap end b but will not be clamped
of the cap to be threaded, said free end portion providing
a cylindrical band of threads adjacent the outer end of
ever, the cap C will tend to tighten itself on the mandrel 75 said mandrel for forming corresponding threads inside the
thereagainst. During the thread forming operation, how
3,087,174
side wall of said cap, a roller assembly providing a plu
projecting outwardly from said support and providing a
free end portion adapted for insertion in the open end
of the cap to be threaded, said free end portion providing
rality of rollers arranged circumferentially around the
free end portion of said mandrel for rolling said cap side
wall into the threads on said mandrel, a movable shoe
a cylindrical band of threads adjacent the outer end of
extending outwardly beyond the outer end of said mandrel,
said mandrel for forming corresponding threads inside
means for holding the outer end of said shoe in engage
ment with the inside surface of the closed end of the
cap as said cap is being threaded, said holding means in
providing a plurality of rollers arranged circumferentially
around the free end portion of said mandrel for rolling
the cylindrical side wall of said cap, a roller assembly
cluding means for rotating said roller assembly relative
said cap side wall into the threads on said mandrel, a
to said cap in such a direction as to tighten said cap 10 movable shoe extending outwardly beyond the outer end
on said mandrel while said cap is being threaded, thereby
of said mandrel, means for holding the outer end of said
holding said closed end away from the outer end of said
shoe in engagement ‘with the inside surface of the closed
mandrel as said cap is ‘being threaded, means for re
end of the cap as said cap is being threaded, thereby hold
tracting said shoe to a position closer to the outer end
ing said closed end away from the outer end of said man
of said mandrel for disengaging said shoe from said cap 15 drel as said cap is being threaded, said means including a
end, whereby said cap can be readily unscrewed from
holding piece providing a face adapted to engage the out
said mandrel after it ‘has been threaded, and means within
side surface of the closed end of said cap as said cap is
said mandrel for movably supporting said shoe.
being threaded, thereby permitting said cap to be clamped
2. The mandrel and roller assembly of claim 1 wherein
between said shoe and said holding piece as said cap is
said mandrel has a longitudinal ‘bore extending inwardly 20 being threaded, said shoe and said holding piece being
from its outer end, and said means for movably support
dimensioned ‘to engage a major portion of the diameter
ing said shoe comprises a pin slidably mounted in said
of said cap, means for retracting said shoe to a position
bore with its outer end adjacent the free end of said man
drel, said shoe being connected to the outer end of said
pin and carried thereby.
closer to the outer end of said mandrel for disengaging
said shoe from said cap end and releasing the clamping
25 engagement between said cap and said holding piece,
3. The mandrel and roller assembly of claim 1 wherein
said means for holding said shoe in engagement with said
cap comprises a compressed air cylinder providing a mov
able piston, and a force transferring linkage extending
from said piston to said shoe, said linkage being arranged 30
so that when air pressure is applied to said cylinder, said
shoe is forced outwardly to a position in engagement with
the cap on said mandrel.
4. A mandrel and roller ‘assembly for use in forming
threads on the inside of a metal cap having a cylindrical 35
side wall and one closed end, comprising a support, a
mandrel ?xedly mounted on said support, said mandrel
whereby said cap can be readily unscrewed from said
mandrel after it has ‘been threaded, and means within
said mandrel for removably supporting said shoe.
References Cited in the ?le of this patent
UNITED STATES PATENTS
‘1,546,091
2,353,253
2,400,024
2,647,553
Lewis ________________ __ July 14,
Liverrnont ____________ __ July 11,
Roehrl ________________ __ May 7,
Sharf _________________ __ Aug. 4,
1925
1944
‘1946
1953
2,799,049
Wilson _______________ __ July 16, 1957
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