U.S. patent number 3,695,087 [Application Number 05/067,007] was granted by the patent office on 1972-10-03 for method and apparatus for pointing tubes.
Invention is credited to Arthur H. Tuberman.
United States Patent |
3,695,087 |
Tuberman |
October 3, 1972 |
METHOD AND APPARATUS FOR POINTING TUBES
Abstract
Method and apparatus for forming a generally cylindrical point
on a tube by first flattening the tube from at least three sides to
a polygonal cross section while forming curved sections between the
flat sides, and then progressively contracting the tube to bring
the curved sections together while buckling the flat sides inwardly
into loops that are flattened inside the point. At least three die
shoes arranged around a die recess in alternately overlapping
relation have flat inner faces with an elongated lip along one side
for shaping the curved sections, and also have flat, inclined
bevels for shaping the transition zone of the tube during pointing,
each bevel having a part-conical lip on one side for the final
shaping of the transition zone to a conical shape. One actuating
arrangement utilizes a mutual camming action to move all die shoes
simultaneously at the same rate to maintain the point on a
preselected axis, while a simpler form displaces the axis during
pointing.
Inventors: |
Tuberman; Arthur H. (Lawndale,
CA) |
Family
ID: |
22073132 |
Appl.
No.: |
05/067,007 |
Filed: |
August 26, 1970 |
Current U.S.
Class: |
72/402;
72/452.8 |
Current CPC
Class: |
B21C
5/00 (20130101); B21C 5/003 (20130101) |
Current International
Class: |
B21C
5/00 (20060101); B21d 041/04 () |
Field of
Search: |
;72/402,367,369,399,400,410,452,468,469,470,472 ;18/DIG.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
372,543 |
|
May 1932 |
|
GB |
|
449,558 |
|
Sep 1927 |
|
DD |
|
1,035,352 |
|
Apr 1955 |
|
DT |
|
397,343 |
|
Aug 1933 |
|
GB |
|
35,625 |
|
Apr 1955 |
|
PO |
|
Primary Examiner: Lanham; Charles W.
Assistant Examiner: Crosby; Gene P.
Claims
I claim:
1. A tube pointer having, in combination:
a case;
a die mounted in said case and comprising at least three die shoes
arranged in alternately overlapped relation around, and defining,
an open-ended recess for receiving one end portion of a tube to be
pointed;
each of said die shoes having a flat inner working face forming one
side of said recess, a side surface in sliding relation with an
extension of the working face of a first adjacent die shoe, and an
extension of its working face in sliding relation with the side
surface of a second adjacent die shoe whereby said shoes are
movable simultaneously inwardly from an open position toward a
closed position and then back outwardly toward said open position
to contract and expand said recess;
a bevel on each of said shoes inclined outwardly from the working
face thereof toward said open end;
an elongated first lip extending along the side of each working
face adjacent the side surface thereof that slides along the
working face of an adjacent block, each of said lips having a
curved inner surface generally tangent to both of the adjacent
working faces and curved about the axis of a tube centered in said
recess;
and a second lip constituting an extension of said first lip on
each of said shoes along one side of the bevel thereon, each of
said second lips having an inner surface of generally conical
curvature flaring toward said open end and generally tangent to
both of the adjacent bevels, whereby said die shoes are movable
progressively inwardly from said open position to contract said
recess about a tube, bend the tube first to a flattened, generally
polygonal cross section with curved sections between the flattened
wall portions, progressively contract the tube polygonally to cause
the flattened wall portions to buckle inwardly, and finally bring
the curved sections together to a substantially cylindrical point
while shaping the tube conically between said second lips.
2. A tube pointer as defined in claim 1 further including means for
moving all of said die shoes simultaneously inwardly at the same
rate and maintaining the point on a preselected axis as it is
formed.
3. A tube pointer as defined in claim 2 in which said moving means
includes actuating means for shifting at least one of said shoes
inwardly at a selected rate, and camming means responsive to
movement of said actuating means and said one shoe to move the
remaining shoes simultaneously inwardly at said rate.
4. A tube pointer as defined in claim 3 in which said camming means
include said extensions of said working faces in sliding and
camming engagement with said side surfaces.
5. A tube pointer as defined in claim 1 in which said die has three
die shoes arranged around said recess with said working faces
forming an equilateral triangle.
6. A tube pointer as defined in claim 1 in which said die has four
die shoes arranged around said recess with said working faces
forming a square.
7. A tube pointer as defined in claim 1 in which said die has more
than four die shoes.
8. A tube pointer as defined in claim 1 in which said curved inner
surfaces are longitudinal sections of a cylinder and move together
to form a cylinder in said closed position.
9. Apparatus for forming a reduced diameter portion on a tube, said
apparatus having, in combination:
at least three die shoes arranged around and defining an open-ended
recess of generally polygonal cross section for receiving the
portion of the tube to be reduced in diameter;
each of said shoes having a substantially flat inner working face
forming one side of said recess, and said shoes being fitted
together for in and out movement in gap-free relation to contract
and expand said recess in generally polygonal cross-sectional
shape;
means on said shoes for changing the shape of said recess from
generally polygonal to generally cylindrical shape as the shoes are
moved inwardly to a selected closed position, whereby the tube
first is flattened to said generally polygonal shape and then is
formed to said generally cylindrical shape; and
means on said shoes for controlling the transition zone of the tube
between said reduced diameter portion and the remainder of the
tube, and including an extension of each working face projecting
outwardly at one end of said recess and inclined away from the tube
to sink progressively into the transition zone at a selected angle
as the recess is contracted in said polygonal cross-sectional
shape, and means on said extensions for closing around said
transition zone in a tapered form of generally circular cross
section as the shape of said recess is changed from polygonal to
cylindrical shape.
10. Apparatus as defined in claim 9 in which said shape-changing
means comprise a curved inner surface on each of said shoes curving
concavely between the working face of the shoe on which it is
formed and the working face of the adjacent shoe, whereby said
generally polygonal cross section has flat sides joined by curved
sections, said curved sections being moved together to said
generally cylindrical shape as said shoes are moved to said closed
position.
11. Apparatus as defined in claim 10 in which each of said
extensions is a bevel that is inclined outwardly from one end of
the working face thereon toward the open end of said recess, and
said means for closing around the transition zone comprises a
second concavely curved inner surface on each of said shoes between
one side of the bevel thereof and the bevel of the adjacent shoe,
said second curved surface being an extension of the first curved
surface and generally in the shape of a longitudinal section of a
cone.
12. Apparatus for forming a reduced-size portion on a tube, said
apparatus having, in combination:
at least three die shoes arranged in alternately overlapped
relation around, and defining, a recess for receiving the portion
of the tube to be reduced in size;
each of said shoes having an inner working face forming one side of
said recess, a side surface in sliding relation with an extension
of the working face of a first adjacent die shoe, and an extension
of its working face in sliding relation with the side surface of a
second adjacent die shoe whereby said shoes are movable inwardly
from an open position toward a closed position and then back
outwardly to contract and expand said recess in polygonal form;
and means for moving said die shoes simultaneously inwardly at the
same rate while a portion of a tube is disposed in said recess,
thereby flattening the tube to the shape of said recess and then
progressively reducing the size of the tube while maintaining the
tube and the reduced-size portion coaxial, said moving means
comprising an actuating member engaging at least one of said die
shoes and operable to shift said one shoe inwardly at a selected
rate, and camming means responsive to movement of said actuating
member and said one shoe for shifting all of said shoes inwardly at
the same rate as said one shoe thereby to maintain said reduced
size portion constantly positioned on a substantially stationary
longitudinal axis.
13. Apparatus as defined in claim 12 in which each of said shoes
has a concavely curved, inwardly facing surface extending along the
side of its working face which slides along the working face of an
adjacent shoe, thereby to form curved sections in the tube between
said working faces and squeeze said curved sections toward each
other as the shoes are moved inwardly, and further including a
bevel on each shoe inclined outwardly from one end of the working
face thereon toward one end of said recess, and a second concavely
curved inner surface on each of said shoes between one side of the
bevel thereof and the bevel of the adjacent shoe, said second
curved surface being an extension of the first curved surface and
generally in the shape of a longitudinal section of a cone.
14. The method of forming a reduced size diameter on one end
portion of a tube, said method including the steps of:
flattening said one end portion from at least three sides thereof
to form the tube into a generally polygonal cross section while
shaping the tube between the sides of said polygonal cross section
into curved sections;
sinking the tube inwardly in controlled tapered fashion from at
least three sides in the zone between said one end portion and the
remainder of the tube;
squeezing said one end portion to shorten said sides and cause them
to buckle inwardly between said curved sections while moving said
curved sections toward each other;
squeezing said zone toward a tapered form of generally circular
cross section;
and continuing such squeezing and buckling at least until said
curved sections are brought substantially together into a reduced
diameter portion and said zone is brought into a tapered form of
substantially circular cross section.
15. Apparatus as defined in claim 12 including a case having inside
guiding surfaces constituting part of said camming means, said
actuating member forming one movable side of said case and having a
V-shaped notch on its inner side forming two of said guiding
surfaces, each of said die shoes having an outer side movable along
one of said guiding surfaces, and two of said outer surfaces being
slidably engaged by said guiding surfaces of said actuating member
during inward movement thereof, the overlapped surfaces of said
shoes cooperating with said outer sides and said guiding surfaces
to cam all of said shoes inwardly at the same rate as said
actuating member moves inwardly.
16. Apparatus as defined in claim 12 further including means for
shifting all of said shoes simultaneously outwardly from said
closed position as said actuating member moves outwardly.
Description
BACKGROUND OF THE INVENTION
This invention relates to the forming of reduced-diameter end
portions on tubes for use in gripping the tubes during an operation
such as drawing through a die. Such reduced-diameter end portions
(called "points" although they typically are generally cylindrical
or have some other blunt-ended shape) are necessary because the
original tubing to be drawn through the die has a larger outside
diameter than the diameter of the die, and also to provide a
portion of the tube that can be gripped securely to apply the
drawing force.
Tube pointing machines of various types are known and have been
used by the trade. For example, U.S. Pat. No. 3,292,414 shows an
apparatus for swaging points with a plurality of arcuate
reciprocating die segments which compress a tube as the arcuate
faces of the dies are pressed together around the tube. Rotary
swaging also has been used. In another, somewhat similar approach,
represented by U.S. Pat. No. 3,073,374, a tube is positioned
between two dies having semi-cylindrical, concave faces and is
pinched and pleated from opposite sides before the semi-cylindrical
dies are closed around the tube.
In still another approach, shown in U.S. Pat. No. 3,068,929, a tube
is positioned over an open-sided, part polygonal recess and then
forced into the recess by two rams which, when moved toward the
open side of the recess, compress the tube into the recess and
cooperate therewith to form a regular polygonal cavity in which the
tube is collapsed and compacted to the desired shape. A similar
result is obtained by the pointer shown in U.S. Pat. No. 3,417,598
in which four dies arranged around the end of a tube are formed
with interleaved flat-edged ribs which permit the dies to be moved
together to crush the end portion of the tube into a point.
While these and other known pointers are capable of producing
usable points on tubes, all of the pointers presently available are
subject to one or more deficiencies that have prevented the
achievement of optimum results. Specifically, many of the machines
produce an excessively high noise level as an incident to the
pointing operation, or require rather complicated and
difficult-to-maintain machinery. More importantly, despite claims
that points can be formed completely in one stroke, it often is
necessary to repeat the forming stroke several times in order to
obtain a proper point, probably because most of the die systems
inherently include gaps into which the metal can be displaced
during pointing. At the same time, it is difficult, if at all
possible, to obtain uniformity in point diameters while maintaining
the points concentric with the tubes.
The configuration of the transition zone between the point and the
body of the tube is particularly important from the standpoint of
performance of the tube during subsequent drawing operations. If
the tube is folded with nonuniform convolutions or distinct
creases, particularly in the transition zone, as is common in some
of the prior pointers, stress risers are set up and can result in
cracks which propagate down the tube during the drawing
operations.
Moreover, many tube materials are "notch sensitive," that is, tend
to break under stress wherever a notch or groove has been formed
during pointing. Thus, any pointer which notches the tube during
pointing, particularly in or around the transition zone, produces a
likelihood of failure during subsequent operations. Of course,
ruggedness, durability and relative simplicity of construction, as
well as economy in construction, operation and maintenance, are
primary objects of any production machine, and certain of the prior
art machines, such as those requiring interleaved ribs, are
deficient in these respects.
SUMMARY OF THE INVENTION
The present invention resides in an improved tube pointer which
produces superior and uniform points in a novel manner by
positively guiding and controlling the bending of the tube material
at all times, both in the zone of the point and in the transition
zone, while eliminating gaps in the die apparatus that could result
in uncontrolled bending or objectionable displacement of the tube
wall. Moreover, the tube pointer of the invention is capable of
forming such points in a single and rapid one-stroke operation, is
relatively simple, durable and quiet in operation, avoids cracks
and objectionable creases in the transition area, and can maintain
the point precisely concentric with the tube, thereby avoiding the
disadvantages or prior pointers.
To the foregoing ends, the pointer includes a die having at least
three die shoes that are arranged around and define an open-ended
die recess of generally polygonal cross section and are interfitted
to permit the shoes to move inwardly and outwardly, radially of the
tube, to contract and expand the recess, the shoes having
substantially flat inner working faces which form the tube first
into a generally polygonal cross-sectional shape as the shoes move
inwardly to contract the recess. The shoes also include means for
shaping the tube between the sides of the polygonal cross section
into arcuate sections so that continued inward movement of the
shoes progressively shortens the sides of the polygonal cross
section to buckle and fold the sides inwardly while moving the
arcuate sections toward each other, finally squeezing the arcuate
sections substantially together into a generally cylindrical point
with the buckled portions formed as flattened loops within the
point.
Controlled formation of the transition zone of the tube is
accomplished by substantially flat bevels on the die shoes which
have the same slope away from the working faces as the desired
angle of the cone of the transition zone, the bevels also having
means thereon for closing conically around the transition zone as
the arcuate sections of the point are brought together. The
controlled buckling of the point zone and the controlled sinking of
the bevels into the tube cooperate to form uniform folds or
convolutions in the transition zone with soft creases that flare
from the point toward the tube into wide and gently rounded ends at
the junction with the tube.
To permit such progressive contraction of die shoes having flat
working faces, the shoes are arranged in alternately overlapped
relation so that an edge of one shoe slides along the working face
of one adjacent shoe, while an edge of the other adjacent shoe
slides along the working face of the first shoe. The illustrative
arcuate shaping means for the point comprise fillets overlying the
junctions between the working faces and having concave inner
surfaces constituting longitudinal sections of a cylinder, and the
corresponding means for the transition zone comprise longitudinal
sections of a cone overlying the junctions between the bevels.
The concentricity of the point and the tube are maintained in the
preferred forms of the invention by moving each die shoe toward the
axis of the tube at the same rate, and this is accomplished with a
single actuator which shifts one of the die shoes toward the axis
at the desired rate while the remaining shoes are cammed inwardly
at the same rate in response to the driving force applied by the
actuator. Thus, the arcuate sections of the shoes can be maintained
concentric with the tube at all stages of the pointing
operation.
Other objects and advantages of the invention will become apparent
from the accompanying detailed description, taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the basic components of a tube
pointer embodying the novel features of the present invention, with
a length of tubing in position for insertion into the pointer, a
representative actuator partially broken away and shown in cross
section, and parts of the pointer shown partly in broken lines for
clarity;
FIG. 2 is an enlarged fragmentary cross-sectional view of the
pointer in FIG. 1, taken substantially along the line 2--2 thereof,
after the tube to be pointed has been inserted in the open die;
FIG. 3 is a view similar to FIG. 2 showing the pointer and tube
after the die has been closed to form the point;
FIG. 3A is an enlarged fragmentary cross section taken
substantially along the lines 3A--3A of FIG. 3;
FIG. 4 is an enlarged fragmentary perspective view of one of the
die shoes of the pointer;
FIG. 5 is a fragmentary plan view of the die shoe of FIG. 4;
FIG. 6 is an enlarged fragmentary perspective view of a pointed
tube;
FIG. 7 is an enlarged end view of a representative tube with the
die shown schematically at the beginning of the pointing
operation;
FIG. 8 is a view similar to FIG. 7 showing the first stage of
bending of the tube during the initial closing of the die in which
the tube is generally polygonal in cross section and the flat sides
are connected by arcuate sections;
FIG. 9 is a similar view showing the next stage of bending as the
walls of the tube begin to buckle during shortening of the flat
sides;
FIG. 10 is a similar view showing the next stage as the buckling
continues and loops begin to form;
FIG. 11 is a similar view showing another stage as the loops are
flattened and compressed and the arcuate sections are brought
together;
FIG. 12 is a cross-sectional view similar to FIG. 2 on a somewhat
reduced scale illustrating an alternative form of the pointer
having four die shoes, the die being open;
FIG. 13 is a view similar to FIG. 12 with the die closed on a
tube;
FIG. 14 is an end view of the pointer in FIG. 12 with a front cover
plate thereof partly broken away;
FIGS. 15 to 19 are sequential views similar to FIGS. 7 to 11
illustrating the bending of a tube to a point with the pointer of
FIGS. 12 to 14;
FIGS. 20 and 21 are views similar to FIG. 14 illustrating an
alternative manner of support and actuation of the die shoes of a
four-shoe pointer;
FIG. 22 is a fragmentary perspective view of a die shoe of the type
used in the pointer of FIGS. 20 and 21;
FIGS. 23 and 24 are fragmentary views showing the arrangement of
die shoes in a pointer having six die shoes, FIG. 23 showing the
open position and FIG. 24 showing the closed position; and
FIGS. 25 and 26 are fragmentary views similar to FIGS. 23 and 24
but showing the arrangement of die shoes in a pointer having eight
shoes.
DETAILED DESCRIPTION
As shown in the drawings for purposes of illustration, and with
specific reference to FIGS. 1-11, the invention is embodied in a
tube pointer 10 for forming a reduced diameter end portion or
"point" 11 (see FIG. 6) on a tube 12, for subsequent use in
gripping the tube and pulling it through a drawing die (not shown)
for a conventional purpose such as redrawing of tubing where the
diameter is to be reduced, the wall thickness is to be changed, and
the like, to obtain the different sizes, shapes and other
characteristics required in industry. The point may be inserted
through such a die and then gripped in a suitable chuck with which
the drawing force is applied.
In general, the pointer 10 includes a pointing die 13 formed by a
set of die shoes which are arranged around and define a recess 14
that is open at one end to receive the end of the tube 12 to be
pointed. The die set is mounted in a case including a top member 15
above the die shoes, side members 17 depending from opposite edges
of the top member, and a bottom member 18 below the shoes. Herein,
the case is supported between a pair of spaced front and rear
guides 19 and 20 upstanding from and bolted to a suitable base 21,
such as a table, and connected by bars 22. Each of the illustrative
guides has upright flanges 23 (FIG. 1) which straddle the front and
rear edges of the side members 17 and support the latter and the
top member 15 for up and down motion, toward and away from the
table 21 and the bottom member 18. This up and down motion is used
to expand and contract the die recess 14 by moving the die shoes
alternately outwardly, away from each other, into the open
condition shown in FIGS. 1 and 2, for insertion of a tube 12 in the
pointer 10, and then inwardly toward each other into the closed
condition (FIG. 3) to compress the portion of the tube within the
die recess and form the reduced diameter point 11 thereon. It
should be understood, however, that this is only one of various
arrangements that may be used to support the die.
In accordance with the primary aspect of the present invention, at
least three die shoes 24, 25 and 26 are arranged around the die
recess 14 and have inner working faces 27 that initially define the
recess with a generally polygonal cross section, and are fitted
together to permit the shoes to be moved simultaneously inwardly,
toward each other, to bend the tube initially to the polygonal
cross section and then to contract the cross section progressively
as such movement continues. In addition, the die shoes have curved
surfaces 28 shaping the portions of the tube between the sides of
the polygonal cross section into curved sections, which are
squeezed progressively toward each other as the die shoes are
closed. Accordingly, the continued shortening of the sides,
accompanying the squeezing of the curved sections toward each
other, causes the portions of the tube between the curved sections
to buckle inwardly in a controlled and predictable manner, forming
loops which are flattened and compressed within the point as the
curved sections are brought together to form the periphery of the
point.
In its broader aspects, the invention also contemplates the control
of the formation of the transition zone 29 of the tube 12 in a
novel manner where the outside diameter increases from that of the
point 11 to that of the body of the tube. For this purpose, each
die shoe 24, 25, 26 has a bevel 30 that is inclined outwardly and
forwardly from the front of the working face 27 at a selected angle
relative to the axis of the tube. These bevels sink progressively
into the tube from all sides as the point is formed, and insure
that the folds or convolutions (indicated generally at 31 in FIG.
6) in the transition zone are formed uniformly and without
objectionable creases or notches. Finally, curved surfaces 32
between the bevels close conically around the transition zone as
the curved surfaces 28 close around the remainder of the point.
In the illustrative embodiment shown in FIGS. 1-5, each die shoe
24-26 is shown as having the flat working face 27 disposed in a
plane parallel to the axis of the tube 12, the three working faces
being identical and cooperating to define the recess 14 with the
general cross-sectional shape of an equilateral triangle, as shown
most clearly in FIG. 2. The three shoes are arranged in alternately
overlapping relation, each having one side edge portion 33 which
abuts slidably against an extension of the working face of an
adjacent shoe on one side, while the corresponding side edge
portion 33 of the other shoe abuts slidably against an extension of
the working face of the first shoe. Thus, all three shoes can be
moved simultaneously inwardly toward the tube axis in mutually
sliding, gap-free relation.
Each side edge portion 33 of a shoe that overlaps the working face
27 of the adjacent shoe herein is formed with an inwardly
projecting, longitudinal lip 34 having an arcuate inner side of
concave curvature constituting the curved surface 28 for shaping
the curved sections of the tube, this surface preferably being
concentric with the tube and tangent to the working face 27 of the
shoe on which it is formed, and also tangent to the working face 27
of the shoe against which the lip slides. Ideally, the arcuate
surface might terminate in a knife edge at 35, but for the
practical purpose of minimizing the likelihood of breakage, this
edge preferably is blunted.
As shown most clearly in FIGS. 3A and 4, the bevels are simply flat
surfaces disposed at suitable forwardly and outwardly inclined
angles with the axis of the tube, for example, five to forty
degrees, depending upon the desired angle of the transition zone.
On one side of each bevel is a flared lip 36 constituting an
extension of the associated lip 34 and having a concave inner side
which preferably is a section of a cone and constitutes the surface
32 for shaping the tube in the transition zone. The free edge of
this lip preferably is blunted for durability and is in the same
plane as the edge of the lip 34.
The actuator of the pointer 10, which may take various forms, moves
all of the die shoes simultaneously inwardly relative to each other
toward the axis of the tube 12 (which may be either stationary or
movable) thereby to close the die 13. During such closing movement,
the overlapping side edge portions 33 slide along the working faces
27 of the adjacent shoes while the working faces themselves remain
parallel to the tube axis. Thus, the working faces first are
pressed against the sides of the tube (three sides as in FIG. 7) in
tangent relation therewith along three longitudinal lines 37, and
then begin to flatten the sides of the tube progressively toward
the triangular condition shown in FIG. 8. Such flattening is
accompanied by initial sinking of the three bevels 30 into the tube
in angularly spaced relation around the portion of the tube within
the flared end portion of the die recess 14 that is defined by the
bevels.
As closing of the die 13 continues, the tube 12 is formed to the
shape shown in FIG. 8 with three flat sides 38, and the
longitudinal portions of the tube between these flat sides are
shaped into arcuate sections 39 which nest firmly against the inner
surfaces 28 of the lips 34. After the die reaches the condition
shown in FIG. 8, further inward motion of the shoes squeezes the
arcuate sections 39 radially inwardly and progressively shortens
the exposed portions of the working faces. The flat sides 38 of the
tube, being confined and backed against outward bulging, begin to
buckle inwardly, as shown at 40 in FIG. 9, and to form loops as
shown at 41 in FIG. 10.
Apparently because there is effective tangential travel of the
working faces 27 as the die 13 is closed, the loops 41 thus formed
are not directed exactly toward the axis of the tube, as might be
expected. Instead, as illustrated in FIG. 10, each loop is offset
slightly from center so that continued crushing of the tube results
in flattening of the loops in an offset, pinwheel fashion as shown
in FIG. 11, thus producing a general symmetry or uniformity in the
cross-sectional configuration of the point. Closing of the die can
be terminated at any selected stage after the generally cylindrical
point 11 has been formed, and, of course, can be continued beyond
the condition shown in FIG. 11 if a denser point is desired. In
fact, with sufficient actuating pressure and appropriately formed
die shoes, the point can be crushed to an essentially solid rod and
even extended in length.
The loops 41 shown in FIG. 10 extend forwardly beyond the working
faces 27 and along the bevels 30, while the arcuate sections 39
extend forwardly and flare outwardly along the concave surfaces 32
constituting sections of a cone. Thus, each transition convolution
31 (FIG. 6) is formed between two arcuate sections of the tube that
are controlled by the conical surfaces, and it has been found that
a rounded crease forms at the bottom of the convolution and spreads
progressively as the convolution flares, being broadly rounded
short of the larger end of the transition zone 29. As closing of
the die is completed, the part-conical surfaces 32 come together
into the desired full-conical shape to form the transition zone to
that shape. The closed, conical condition is shown most clearly in
FIG. 3A, and also in FIG. 21 with regard to a four-shoe form of the
pointer, hereinafter described in detail.
The preferred manner of actuation of the pointer 10 is the cam
arrangement illustrated in FIGS. 2 and 3 wherein it will be seen
that the upper die shoes 24 and 26 are arranged generally in the
shape of an inverted "V" with inclined, upwardly facing outer sides
42 and 43 parallel to the working faces 27 of the shoes and nested
against similarly inclined, downwardly facing surfaces 44 and 45 on
the underside of the top member 15 of the case. The third die shoe
25 is generally triangular in shape and has an outer side 47 that
is inclined upwardly and to the left, and the overlapped side edge
33 is inclined downwardly and to the right beyond the overlapping
portion of the working face 27 of the shoe 24. Rollers 48 are
disposed between the inclined outer side 47 and an inclined,
parallel upper surface 50 of the bottom member 18, thus supporting
the lower die shoe 25 for movement upwardly and to the left along
the inclined surface 50 of the bottom member.
A coiled extension spring 51 is stretched between two pins 52 and
53 respectively mounted in a recess 54 in the bottom member 18 and
a recess 55 in the lower die shoe 25, thus urging the shoe
downwardly toward the position shown in FIG. 2 and holding it
firmly against the rollers 48, which may be maintained in spaced
parallel relation by rack-and-pinion mechanisms 57 at their ends,
as shown in FIG. 1. A similar spring 58 for holding the upper right
die shoe 24 against the surface 44 is stretched between pins 59 and
60 on the top member 15 and the shoe, although it will be seen that
this shoe does not move relative to the upper member during
actuation of the pointer. The spring merely holds the die shoe
firmly in place against the surface 44 and forms a releasable
connection facilitating changing of the die.
The die shoe 26 may be similarly spring positioned, but preferably
is controlled by a hydraulic cylinder formed by a blind bore 61
which parallels the inclined surface 45 of the top member and
telescopingly receives the lower end portion of a plunger 62 that
is formed with a longitudinal through passage 63. This passage
communicates at its lower end with the bore 61 and at its upper end
with a conduit 64 for receiving fluid under pressure from an
external source (not shown) through a fitting 65. This cylinder
forms, in effect, a hydraulic spring which returns the shoe 26 and
the top member 15 to the positions shown in FIG. 2 to open the die
13 after each pointing operation.
With the foregoing arrangement, the parts are disposed in the
positions shown in FIG. 2 prior to each pointing operation, and a
tube 12 may be inserted in the open die recess 14 in the manner
shown, with sufficient clearance around the tube to permit easy
insertion. If desired, a tube guide (not shown) may be mounted on,
or in front of, the front guide 19 to position the tube for the
pointing operation.
With the tube properly positioned, a ram 67 abutting against the
top member 15 is actuated to force the top member and the side
plates 17 downwardly relative to the bottom member 18, thus forcing
the right upper die shoe 24 downwardly along the right side of the
lower die shoe 25. As the right shoe slides along the lower shoe,
the abutting inclined surfaces 33 and 27 of the shoes cooperate to
cam the lower shoe to the left, and the upwardly inclined surface
50 of the bottom member 18 simultaneously guides the lower shoe
upwardly and inwardly at a rate determined by the slope of the
surface 50. At the same time, this upward motion of the lower shoe
is transferred to the lower edge 33 of the left shoe 26 through the
overlapped sides of the two shoes, and is combined with the
downward motion of the top member 15 to produce an inward (to the
right) motion of the left die shoe at a rate determined by the
slope of the inclined surface 45 and the rate of movement of the
left shoe along this surface.
Accordingly, with properly correlated slopes on the various cam
surfaces, the three die shoes 24-26 are moved simultaneously and at
the same rate toward the axis of the tube 12. Termination of this
closing movement can be controlled in various ways, for example, by
one or more limit switches (not shown) actuated in response to
movement of the die shoes to selected positions, the limit switches
preferably being adjustably positioned for selective variation of
the point of termination. The same switching arrangement that
terminates the closing stroke also can automatically initiate the
following opening stroke.
During opening of the die recess 14, the three shoes 24-26 move
reversely along the paths followed during closing, the right shoe
24 being raised as the top member 15 is raised by the hydraulic
cylinder 61, 62, thereby permitting the lower shoe 25 to be
returned along the surface 50 by the spring 51 and the left shoe 26
to be lowered along the surface. An additional switching
arrangement can be provided to terminate the opening stroke as the
die shoes return to the position in FIG. 2. The details of such
switching arrangements, including manual or timed automatic
actuation, are well known in the art and therefore are not
described in detail herein.
FIRST ALTERNATIVE EMBODIMENT (FIGS. 12-19)
It has been stated that at least three die shoes are believed to be
necessary in order to define a gap-free die recess capable of being
closed around a tube in accordance with the present invention. It
should be emphasized, however, that the invention is not limited to
the use of three die shoes, and that, in fact, different
circumstances may make the use of four or more shoes
advantageous.
Since each die shoe produces one fold or convolution in the tube
in, and adjacent to, the point, changes in the number of shoes will
result in different numbers and angular spacings of the
convolutions. With tubes having walls with a relatively high
thickness-to-diameter ratio, it is relatively difficult to buckle
and fold the tube wall, so the use of a lesser number of shoes will
form the folds farther apart, angularly, around the tube and insure
that the wall sections will buckle inwardly from the polygonal
stage rather than feeding peripherally around the inner surfaces of
the die. For tubes having walls with a relatively low
thickness-to-diameter ratio, a greater number of die shoes are used
to provide better control of the relatively easy-to-fold tube
walls.
In the pointer 70 shown in FIGS. 12-14, in which some
corresponding, generally similar parts are indicated by
corresponding reference numbers it will be seen that four die shoes
71-74 are arranged around and define the die recess 14, which thus
is generally square in cross section when the die is open. As
before, these die shoes have flat inner working faces 27 in planes
parallel to the axis of the tube 12, are arranged in alternately
overlapped relation permitting closing movement of the die shoes in
the square or rectangular form, and have lips 34 with curved inner
surfaces 28 preferably consituting longitudinal sections of a
cylinder.
In addition, as shown in FIG. 14, each die shoe 71-74 has a bevel
30 from the forward end of the working face 27 to the front side of
the shoe, and each bevel merges smoothly with a part conical
surface 32 for shaping the transition zone 29 of the tube as the
die is closed, forming the full conical surface around the tube as
can be seen in the similar form shown in FIG. 21.
The four die shoes 71-74 of FIGS. 12-14 are mounted and actuated in
substantially the same way as the three shoes in FIGS. 1-5, being
mounted in a case including a fixed bottom member 18, two
upstanding side plates 17 which in this instance are fastened to
the side edges of the bottom member, and a top member 15 which is
movable vertically between the side plates. A ram 67 engages the
top member to apply the force necessary to push the top member down
and close the die around the tube 12, and a front plate 75 is
bolted to the bottom member and the side plates to close the front
of the case except for an aperture 77 (FIG. 14) formed therein to
admit the tube into the die recess 14.
In this instance, the upper right die shoe 71 is detachably
connected to the top member 15 by a spring 78 and remains
stationary during actuation of the pointer 70, as did the shoe 24
in the first form, and the lower right shoe 72 is slidable
horizontally across the top surface 50 of the bottom member in
response to the camming action of the downwardly and rightwardly
inclined working face 27 of the upper right shoe 71 on the abutting
inclined side 33 of the lower right shoe. A spring 79, stretched
between the shoe and the adjacent side plate 17, yields during
closing of the die and then returns the shoe to the right when the
closing force is relieved.
The lower left shoe 73 slides vertically along the left side plate
17 in response to the camming action of the the inclined face 27 of
the lower right shoe 72 on the abutting inclined side 33 of the
lower left shoe, and is urged yieldably toward the bottom member 18
by a spring 80. The upper left shoe 74, as before, is guided along
an upwardly and rightwardly inclined wall 45 of the top member 15,
and also is cammed inwardly and upwardly by the inclined face 27 of
the lower left shoe 73, this face abutting against the inclined
edge 33 of the upper left shoe. A blind bore 61 is formed in the
upper left block and telescopingly receives a plunger 62, thus
forming a hydraulic cylinder which opens the die set in the same
manner as in the first form.
As shown in FIGS. 15-19, the bending of the tube wall follows the
same sequence as in FIGS. 7-11, the only significant difference
being the formation of a generally rectangular initial cross
section with four sides 81 (FIG. 16) joined by four arcuate
sections 82. This is followed by the buckling of the four sides at
83 (FIG. 17), the formation of loops 84 (FIG. 18) which are
slightly offset from center, and the collapse of the loops into the
generally cylindrical point 85 (FIG. 19). From this collapsed
condition, the point may be further compressed to a smaller
diameter and greater density, as desired. Of course, the formation
of the transition zone of the tube follows the same procedure as
before, with the addition of one fold or convolution.
SECOND ALTERNATIVE EMBODIMENT (FIGS. 20-22)
The pointer 90 shown in FIGS. 20 and 21 is similar to the first
alternative embodiment in that it has four die blocks 71-74
(corresponding reference numbers being used in both of these forms,
where applicable), but in this case the closing of the die results
in displacement of the axis of the die recess 14 and the tube
point, downwardly in parallel from the original position. Thus,
this pointer is suited for use under circumstances which permit the
tube to be moved during the pointing operation so as to follow the
movement of the point and remain at least generally coaxial
therewith.
As will be seen most clearly in FIG. 21, the configuration and
arrangement of the four die shoes 71-74 are virtually the same as
in FIGS. 12-14. The shoes may be identical in shape, however, with
outer sides 91 parallel to the working faces 27 and with opposite
end surfaces 92 and 93 in planes that are perpendicular to the
inner and outer surfaces. Actuating plates 94 are fastened, as by
bolting, to the outer sides 91 with one projecting end portion 94a
of each plate overhanging the end surface 93 of an adjacent shoe,
in spaced parallel relation therewith when the die is open (FIG.
20). Coiled compression springs 95 are disposed between these
overhanging portions and the adjacent end surfaces to urge the die
shoes toward the open positions. Herein, the springs are held in
place by bores 97 which extend into the shoes so that the springs
are compressed between the actuating plates and the ends of the
bores. Thus, the springs urge the plates 94 away from the ends of
the shoes, and thereby urge the die shoes toward the open condition
shown in FIG. 20.
The two lower shoes 72 and 73 are nested in a V-shaped groove or
notch in the bottom member 18 with the associated actuating plates
94 resting against the walls of the notch, and the two upper shoes
71 and 74 are similarly nested in an inverted V-shaped notch in the
underside of the top member 15. In this instance, the side plates
17 are fastened to the top member and extend downwardly along, and
slide against, the sides of the bottom member.
As the top member 15 is forced downwardly by the ram 67, the two
upper die shoes 71 and 74 are forced downwardly toward and against
the tube 12, the upper right shoe 71 moving substantially straight
down and camming the lower right shoe 72 downwardly to the left,
deeper into the lower notch. As this happens, the lower left shoe
73 remains substantially stationary and the upper left shoe 74 is
cammed upwardly to the right and deeper into the upper notch.
Accordingly, the die is closed as before, but the axis of the die
recess moves progressively lower during such closing, from the
level shown in FIG. 20 to the level in FIG. 21, the springs 95
being compressed between the die shoes and the actuating plates as
an incident to the closing. Subsequently, as the ram 67 is
retracted, the springs return the die shoes to the open condition
of FIG. 20. The actuating plates 94 prevent a combined rotation
effect of the die shoes that could be present if the springs were
to bear against the surfaces of the notches in the top and bottom
members.
ADDITIONAL ALTERNATIVE EMBODIMENTS (FIGS. 23-26)
The schematic views in FIGS. 23-26 are included to illustrate die
arrangements for larger numbers of die shoes, six in FIGS. 23 and
24 and eight in FIGS. 25 and 26. It will be seen that the initially
exposed portions of the working faces 27 become progressively
shorter, in proportion, as the number of die shoes is increased,
thus forming initial folds of shorter angular extent, and the arcs
of the arcuate surfaces 28 are similarly changed as the final
cylinder is divided into a larger number of longitudinal sections
that are distributed around the die as parts of the die shoes.
From the foregoing, it will be seen that the present invention
provides a novel apparatus for forming reduced diameter portions or
"points" on tubes, and uses a similarly novel method of reducing
the diameter to a substantially similar point. In each embodiment
illustrated and described, the alternately overlapping die shoes
are movable in gap-free relation from an open position in which the
flat inner working faces of the shoes define a die recess of
regular polygonal shape with curved surfaces between the flat
sides, thus forming the tube to the same polygonal shape with
curved longitudinal sections as an incident to the initial closing
movement of the die shoes.
Moreover, continued closing movement in each case progressively
shortens the flat sides while squeezing the curved sections toward
each other, causing the flat sides to buckle inwardly and form
loops that may be flattened in a relatively uniform manner within
the point.
The result is a die apparatus and pointing method which produce
improved points in a highly effective manner, with a relatively
simple die structure of competitive initial cost and relatively
rugged and durable construction, and with a smooth and continuous
stroke that normally is effective to form the point in a simple,
rapid and quiet operation. Accordingly, the present invention
avoids disadvantages that have been inherent in prior pointers,
while forming a controlled point without notches, creases or other
irregularities that could interfere with proper performance in a
later operation.
* * * * *