U.S. patent number 3,572,080 [Application Number 04/764,875] was granted by the patent office on 1971-03-23 for production of pointed workpieces.
This patent grant is currently assigned to George A. Mitchell Company. Invention is credited to Peter Alexoff, Fred E. Halstead, George A. Mitchell.
United States Patent |
3,572,080 |
Alexoff , et al. |
March 23, 1971 |
PRODUCTION OF POINTED WORKPIECES
Abstract
Described are a method an apparatus for pointing long slender
workpieces, characterized in that concentric, telescoping dies of
successively smaller cross-sectional areas are forced over the end
of the workpiece to thereby progressively reduce its
cross-sectional area in steps. Also described are a method and
apparatus for preventing bowing or curving in a point formed by
forcing a die over a workpiece to extrude the point.
Inventors: |
Alexoff; Peter (Poland, OH),
Mitchell; George A. (Youngstown, OH), Halstead; Fred E.
(Wynne, AR) |
Assignee: |
George A. Mitchell Company
(Youngstown, OH)
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Family
ID: |
25072040 |
Appl.
No.: |
04/764,875 |
Filed: |
October 3, 1968 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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681291 |
Nov 7, 1967 |
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Current U.S.
Class: |
72/273.5 |
Current CPC
Class: |
B21C
5/003 (20130101); B21C 5/00 (20130101) |
Current International
Class: |
B21C
5/00 (20060101); B21c 005/00 () |
Field of
Search: |
;72/370,347--49,280--85,367,354 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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774,985 |
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Oct 1934 |
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FR |
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942,599 |
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Sep 1948 |
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FR |
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730,633 |
|
Jan 1943 |
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DD |
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843,186 |
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Aug 1960 |
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GB |
|
Primary Examiner: Herbst; Rchard J.
Parent Case Text
CROSS-REFERENCE TO RELATED PATENTS
This application is a continuation-in-part of copending application
Ser. No. 681,291, filed Nov. 7, 1967, now abandoned.
Claims
We claim:
1. In apparatus for forming a point on the end of a long slender
workpiece, the combination of means for clamping the workpiece in
place at a fixed location, a crosshead reciprocable toward and away
from an end of said workpiece, a die carried on said crosshead and
adapted to be forced over the end of the workpiece to produce a
point of reduced cross-sectional area when said crosshead is forced
toward the workpiece, a member having a generally conical surface
which engages an edge of the end surface of said workpiece as said
die is forced thereover to prevent said end from bowing from the
longitudinal axis of the workpiece, said member being reciprocable
along said axis, and means for yieldingly urging said member toward
said crosshead whereby the member will move forwardly with said
crosshead as the die is forced over said workpiece until the end of
the workpiece engages said generally conical surface, whereupon
further forward movement of said member with the crosshead is
terminated and the pointed end of the workpiece is prevented from
bowing by engagement with said generally conical surface.
2. The apparatus of claim 1 wherein said means for yieldingly
urging said member toward said crosshead comprises fluid cylinder
means having a piston rod coaxial with said axis of the workpiece,
said member being carried on the end of said piston rod and said
conical surface being on the side of said member opposite the
piston rod, and means for pressurizing said fluid cylinder to
yieldingly urge said member toward said crosshead, the pressure
exerted by said fluid cylinder being such that forward movement of
the member with the crosshead will stop when the generally conical
surface on the member engages said end surface of the
workpiece.
3. The apparatus of claim 1 wherein said means for clamping the
workpiece in place comprises a first cradle, a second cradle
movable toward and away from the first cradle, clamping members
carried in the cradles, each of the clamping members having a
plurality of sides, and semicircular channels of different
diameters formed in said dies and extending parallel to the axis of
an article to be clamped, each channel in one member being of the
same diameter as a corresponding channel in the other member
whereby the members can be rotated to place the same sized channels
in juxtaposition for reception of a workpiece to be clamped.
4. The apparatus of claim 1 including a plurality of crossheads
each of which carries an associated die, the dies on successive
crossheads being of successively smaller diameters and coaxial with
the axis of said workpiece, means for forcing the crosshead
carrying the die of largest diameter along the axis of said
workpiece whereby the die of largest diameter will pass over the
end of said workpiece, means for forcing at least a second
crosshead carrying a die of smaller diameter along the axis of said
workpiece whereby said die of smaller diameter will pass over the
reduced cross-sectional area formed by said largest diameter die
while the first-mentioned die remains on the workpiece, said
generally conical surface on said member engaging said end surface
of the workpiece after said die of smaller diameter has passed
thereover.
5. The apparatus of claim 1 including hydraulic cylinder means for
forcing said crosshead and the die carried thereby toward said
workpiece, and wherein said means for yieldingly urging said member
toward said crosshead comprises a pneumatic cylinder which exerts a
force less than the force exerted by said hydraulic cylinder
means.
6. The apparatus of claim 1 wherein said crosshead carries a
plurality of dies of successively smaller diameters, and means on
said crosshead for moving successive ones of said dies into
alignment with the axis of said workpiece.
Description
BACKGROUND OF THE INVENTION
As is known, in a conventional tube drawing operation, the reduced
diameter end of a tube, mounted on a mandrel, is passed through a
die and engaged by gripper jaws on a draw carriage or dolly which
travel on a track or guideway on one side of the die. After the
reduced diameter end of the tube is passed through the die and
engaged by the aforesaid gripper jaws, the draw carriage is forced
to move away from the die, thereby pulling the tube through the
die. In this process, the diameter and wall thickness of the tube
are decreased while its length increases. In a similar manner, bars
are drawn on drawbenches by initially pointing an end thereof, the
pointed end being engaged by jaws on a draw carriage which moves
away from the die to thereby pull the bar through the die.
In the past, the problem of pointing tubes or bars to be cold drawn
has been accomplished in many different ways, both at the drawing
equipment as an integrated function thereof, and as an auxiliary
process which occurs prior to the material being delivered to the
drawbench for drawing. The most commonly used method for pointing
bars and tubes has been with the use of hammer swaging equipment.
This type of operation, however, is noisy and time consuming, and
also requires high maintenance on the swaging machine. Furthermore,
in the case of certain types of metals, the point produced by
hammer swaging is worked by repeated blows of the hammers to the
extent that it is brittle and subject to breakage when drawn.
Another problem exists with hammer swaging machines where a tube of
relatively large diameter and thin wall thickness is to be pointed.
This requires a relatively large and high priced machine for the
reason that the size of the machine is dictated by the initial
outer diameter of the tube, notwithstanding the fact that little
actual work must be done to swage or reduce the thin wall of the
tube.
Another pointing device used on heavy size tubes is the multiple
hydraulic cylinder squeeze pointer that works on the point in
steps, resulting in a very rough, long point. The operation, even
though universally accepted for larger sizes, is slow and requires
high maintenance.
On tubing, one of the most practical types of pointing equipment
has been that which produces a folded-type point. Such apparatus is
shown, for example, in copending application Ser. No. 451,296,
filed Apr. 27, 1965. By reference to that application, it will be
seen that the apparatus deforms or squeezes the end of a tube
between a pair of opposing dies to produce a cross-sectional
configuration of reduced diameter wherein the wall of the tube
forms a more or less S-shape. This pointer has no equal from the
point of view of lack of noise, ease of feeding material to the
dies, and speed of operation. It does, however, have some
drawbacks. When the wall thickness of the tube is nonuniform, the
fold is more pronounced on one side of the tube than the other,
resulting in an offcenter, misformed point. Another problem which
exists with this type of pointer is that the conical transition
between the reduced diameter point and the remainder of the
undeformed tube sometimes has irregularities which raise the
possibility of tube points pulling off under the most severe
drawing conditions.
Another disadvantage of fold pointing is that in certain tube
drawing operations where the tubes are immersed in a lubricant or
cleaning acid, the closed end prevents or impedes drainage of
lubricant from the interior of the tube. Also, where the tubing is
to be drawn on a bull block, it is necessary to insert a floating
mandrel into the tube prior to the pointing operation. If the
floating mandrel happens to slide into the area of the tube to be
pointed, a subsequent attempt to deform the end of the tube in a
press or hammer swaging machine will cause extensive damage to the
pointing equipment.
In an effort to overcome the disadvantages of the pointing devices
which squeeze or fold the end of the tube into a compact mass,
attempts have been made to apply push-pointing techniques to the
production of pointed tubing. In the push-pointer, the material to
be pointed is aligned with a die opening of smaller cross-sectional
area than the workpiece. A set of jaws on one side of the die
usually grip the workpiece and thrust it through the die, thereby
reducing the diameter of the forward end of the tube as it passes
through the die.
Push-pointing has been used rather extensively on bars where the
cross-sectional reduction per draw is quite low; however, until
recently it has not been used on tubing primarily because of the
fact that the required outside diameter reduction on tubes is
usually quite large and requires a rather heavy thrust to push the
tube through the die. This would normally cause the tube to fail in
compression before it could be pushed through the die.
Deformation of the tube during push-pointing can be eliminated by
forming the tube gradually and in successive push-pointing
operations. That is, the end of the tube is passed through a first
die having a cross-sectional area less than the original
cross-sectional area of the workpiece, and thereafter passed
through at least one other die having a cross-sectional area less
than that of the first die whereby the cross-sectional area of the
end of the tube is reduced in successive steps. Since the tubes are
push-pointed in successive operations, the reduction taken in any
successive step is not much as to cause failure in compression.
In the past, push-pointing apparatus for tubing employing
successive dies required that the tube be aligned with a first die
and pushed through that die, thereafter withdrawn from the first
die, and then aligned with the second and succeeding dies where the
foregoing cycle was repeated. As will be understood, this process
is rather slow and cumbersome.
Furthermore, it has been found that when a die is formed over a
tube to form a point, there is a tendency for the point to become
bowed or curved as it is extruded through the die, the reason being
that ordinarily there is nothing to support the forward end of the
tube during the push-pointing operation. This condition cannot be
tolerated, particularly where successive dies are utilized to form
the point since the point must remain in alignment with the
longitudinal centerline of the tube to permit successive dies to
pass thereover.
SUMMARY OF THE INVENTION
In accordance with the present invention, reduced diameter points
are formed on the ends of long slender workpieces of predetermined
cross-sectional area and particularly tubing, by the steps of
initially clamping the workpiece in place, forcing a first die of
cross-sectional area less than said predetermined cross-sectional
area over the end of the workpiece to produce a reduced
cross-sectional area end, and forcing at least one other die over
said reduced cross-sectional area end while the first die remains
stationary on the workpiece, the second and any succeeding dies
having cross-sectional areas smaller than that of the preceding die
whereby the cross-sectional area of the end of the workpiece is
reduced in successive steps.
As the successive dies are forced over the end of the workpiece, it
is extruded, thereby causing its length to increase. Thus, whereas
most pointing operations for tubes simply attempt to squeeze or
fold the tube into a compact point, the present invention provides
means whereby the end of the tube is extruded by successive dies
into a point of increased wall thickness and greatly reduced
cross-sectional area. At the same time, the tube is not completely
closed such that lubricant, for example, can escape from the
pointed end; and since the dies are pushed over the tube, no danger
exists of damage to the pointing apparatus because of a
floating-type mandrel being lodged in the section of the tube being
pointed. That is, if the mandrel should be lodged in the area being
pointed, it simply will be pushed backwardly as the dies are forced
over the end of the tube.
Further, in accordance with the invention, high pressure hydraulic
cylinders are utilized to force at least one die over the forward
end of a workpiece, while a relatively low pressure air cylinder is
utilized to urge a cup-shaped member over the forward end of the
point as it is being formed by the die. In this manner, the
pressure of the cup-shaped member against the end of the point
prevents it from becoming bowed or curved. In the case of multiple
dies, the cup-shaped member and air cylinder force those dies
following the die being pushed over the tube against the tube end
to maintain it straight until the last die passes over the point,
whereupon the cup-shaped member itself engages the end of the
point.
The above and other objects and features of the invention will
become apparent from the following detailed description taken in
connection with the accompanying drawings which form a part of this
specification, and in which:
FIG. 1 is a top or plan view of one embodiment of the tube pointing
apparatus of the invention;
FIG. 2 is a cross-sectional view taken substantially along line
II-II of FIG. 1;
FIGS. 3A--3D graphically illustrate the operation of the embodiment
of FIGS. 1 and 2 in producing a pointed tube by successive
push-pointing steps;
FIG. 4 is a top view of another embodiment of the invention;
FIG. 5 is an end view of the embodiment of the invention shown in
FIG. 4;
FIGS. 6A--6E illustrate the operation of the embodiment of FIGS. 4
and 5;
FIG. 7 is a cross-sectional view of still another embodiment of the
invention employing a single crosshead having a plurality of rotary
dies thereon;
FIG. 8 is a cross-sectional view taken substantially along line
VIII-VIII of FIG. 7; and
FIG. 9 is an end view taken substantially along line IX-IX of FIG.
7.
With reference now to the drawings, and particularly to FIGS. 1 and
2, the tube pointing apparatus shown includes a pair of side
members 10 and 12 interconnected at one end by means of a mounting
block 14 and at the other end by means of blocks 16 and 17 (FIG.
2). Extending between the side members 10 and 12 is a channel
member 18 which supports a circular bearing housing 20. The bearing
housing 20, at the ends of its inner peripheral surface, is
provided with bushings 22 and 24 (FIG. 2) which receive the first
cylinder of a set of three telescoping cylinders 26, 28 and 30.
As shown, the first or outer telescoping cylinder 36 slides within
the bushings 22 and 24 and is connected, at its trailing end, to a
crosshead 32. The intermediate cylinder 28 is separated from
cylinder 26 by means of bushings 34 and 36. Likewise, it is
separated from the cylinder 30 by means of bushings 38 and 40. The
right end of cylinder 28, as viewed in FIG. 2, is connected to a
second crosshead 42; while the central cylinder 30 is provided at
its right end with a plug 44.
The cylinder 26 and its crosshead 32 are caused to reciprocate by
means of a pair of hydraulic cylinders 46 and 48 (FIG. 1) mounted
on either side of the block 14 and having piston rods 46 a and 48a
passing through openings 50 in crosshead 42 and connected to the
crosshead 32. In a somewhat similar manner, the cylinder 28 and its
crosshead 42 can be caused to reciprocate by means of hydraulic
cylinders 52 and 54 (FIG. 2) mounted at the top and bottom of the
block 14 intermediate cylinders 46 and 48. Cylinders 52 and 54 are
provided with piston rods 52a and 54a which are connected to the
crosshead 42. Finally, the innermost cylinder 30 is reciprocated by
means of a hydraulic cylinder 56 centrally mounted on the block 14
and having a piston rod 56a threaded to the plug 44 on the end of
cylinder 30. Machined into the left ends of the cylinders 26, 28
and 30 are enlarged diameter portions 58, 60 and 62, respectively,
which receive push-pointing dies in a manner hereinafter described
in connection with FIGS. 3A--3D.
In the operation of the push-pointing apparatus, the cylinders 46
and 48 are initially pressurized to force the crosshead 32 and the
outer telescoping cylinder 26 to the left as viewed in FIG. 2.
During this time, the piston rods 46a and 48a simply slide through
the openings 50 in crosshead 42. Thereafter, cylinders 52 and 54
are pressurized to move crosshead 42 and the intermediate cylinder
28 to the left. Finally, the single cylinder 56 is pressurized to
move the innermost cylinder 30 to the left. After a push-pointing
operation, all of the cylinders 26, 28 and 30 are preferably moved
to the right simultaneously.
A tube to be pointed is illustrated schematically in FIG. 2 and
identified by the reference numeral 64. This tube is clamped in
position during a pointing operation by means of a pair of opposing
jaws, generally indicated by the reference numerals 66 and 68. The
jaw 66 is stationarily mounted on the plates 16 and 17. Beneath the
stationary jaw 66 is a block 72 which extends between plates 16 and
17; and extending between the block 72 and the upright portion of
side member 12 are two traverse rods 74 and 76. The rods 74 and 76
carry, for reciprocating movement, the jaw 68. In order to secure a
tube to be pointed between the jaws 66 and 68, the jaw 68 is
initially moved away from jaw 66 on rods 74 and 76; the tube
inserted between the jaws; and jaw 68 then moved toward the jaw 66
in order to secure the tube in place.
Apparatus for reciprocating the jaw 68 on rods 74 and 76 includes a
hydraulic cylinder 78 (FIG. 1) having its one end pivotally
connected at 80 to a bracket 82 secured to the upright portion of
side member 12. The piston rod 84 of cylinder 78 is pivotally
connected at 86 to a bar 88. The bar 88, in turn, is provided with
two pins 90 and 92 which pivotally support sets of links 94, 96 and
98, 100. The links 94 and 98 are pivotally connected to pins 102
and 104 carried on the jaw 68; while the links 96 and 100 are
pivotally connected to pins 106 and 108 carried on a crossplate 110
which is, in turn, connected to plates 16 and 17.
With the arrangement shown, movement of the piston rod 84 to the
left as viewed in FIG. 1 will cause the bar 88 to move to the
dotted line position shown, thereby pulling jaw 68 away from jaw
66. However, upon reversal of the piston rod 84 and bar 88, the jaw
68 is forced toward the jaw 66, thereby securing the tube 64
therebetween.
With reference now to FIGS. 3A--3D, the manner in which
push-pointing occurs is shown. The tube 64 to be pointed is clamped
or secured between the jaws 66 and 68. In the illustration given,
the tube 64 is to be drawn on a bull block. Accordingly, before the
pointing operation begins, a floating mandrel 112 is inserted into
the tube. In the case of a floating mandrel, pins 114 and 116
embedded in the jaws 66 and 68 indent or dimple the tube 64 behind
the floating mandrel 112. This insures that the mandrel becomes
lodged between the interior of the tube and the die at the
initiation of a bull block drawing operation. As soon as the
drawing operation begins, the dimpled portions formed by the pins
114 and 116 are pulled over the mandrel 112; however by this time
the mandrel is securely lodged within the tube at the location of
the drawing die. Of course, if the tube is to be drawn on a
conventional drawbench where the mandrel is anchored at the end of
a mandrel table opposite the drawing die, the dimples are
unnecessary and the pins 114 and 116 may be removed from the
jaws.
Carried within the enlarged diameter portion 58 of the outer
cylinder 26 is a first die 118. Similarly, a second die 120 is
fitted into the enlarged diameter portion 60 of cylinder 28.
Finally, the die 122 having a smaller diameter than that of the die
20 is fitted into the enlarged diameter portion 62 of the cylinder
30. An end cap 124 is threaded onto the end of the outer cylinder
26 to assist in preventing removal of the dies 118--122 from their
seats upon removal of the dies from the pointed tube in a manner
hereinafter described.
The pointing operation begins by pressurizing hydraulic cylinders
46 and 48 shown in FIG. 1 to thereby force the cylinder 26 and die
118 to the left as viewed in FIGS. 3A and 3B. As the die 118 is
forced over the tube 64, the cross-sectional area of its forward
end is reduced such that it now has a diameter d.sub. 2 which is
smaller than the original diameter d.sub. 1 of tube 64. In this
process, the forward end of the tube is extruded such that its
length is increased by an amount equal to .DELTA.L1. Following the
first reduction process, therefore, the tube appears as in FIG. 3B.
The cylinders 52 and 54 are now pressurized to move the cylinder 28
and die 60 to the left as viewed in FIG. 3C. Note that the die 120
has a diameter d.sub. 3 which is smaller than the diameter d.sub. 2
produced by the die 118. Again, the length of the tube is increased
by extrusion in the amount .DELTA.L2. Finally, the single cylinder
56 is pressurized to force the die 122 over the end of the
previously extruded tube as shown in FIG. 3D whereby the end of the
point now assumes the diameter d.sub. 4 and has increased in length
in an amount equal to .DELTA.L3. At the completion of the pointing
operation, hydraulic cylinders 46 and 48 are pressurized to
withdraw all of the cylinders 26--30 and their associated dies
118--122 to the right, whereupon the jaws 66 and 68 are opened to
remove the now-pointed tube 64.
As the dies 118--122 are pushed over the end of the tube to form an
extruded point as shown in FIGS. 3A--3D, there is a tendency for
the point to become bowed or curved in the extrusion process. This
is particularly true as the diameter of the point becomes
increasingly smaller; and even through the point must be pulled
back through the dies at the completion of a pointing operation,
this bowed or curved condition may still persist.
Apparatus for eliminating the curved condition of the point is
shown, in one embodiment, in FIGS. 4 and 5. It again includes side
members or channels 130 and 132 which support, at one end, a
clamping mechanism 134 similar to the clamping mechanism already
described in connection with FIGS. 1 and 2. The clamping mechanism
134 again includes a stationary clamping member 136, a movable
clamping member 138, an actuating cylinder 140 and a linkage
mechanism 142 interconnecting the cylinder and the movable clamping
member 138 whereby the member 138 may be moved toward or away from
a tube positioned between the two die members 136 and 138. In this
respect, the clamping mechanism is the same as that shown in FIGS.
1 and 2.
At the other end of the channels 130 and 132 is a mounting block
144. Between the block 144 and upright channels 146 and 148
supported on the side channels 130 and 132, respectively, are
cylindrical slides or columns 150 and 152. Slideable on the columns
150 and 152 are three crossheads 154, 156 and 158. The crossheads
154--158 are perhaps best shown in FIG. 6A and carry dies 160, 162
and 164, respectively. As will be explained hereinafter, the dies
160--164, have successively decreasing diameters as was the case
with the embodiment of the invention shown in FIGS. 3A--3D.
Referring still to FIG. 6A, the crosshead 154 is connected through
piston rods 166 to a first pair of hydraulic cylinders 168 and 170
(FIGS. 4 and 5) mounted at the top and bottom of the mounting block
144. Similarly, the crosshead 156 is connected through piston rods
172 (only one of which is shown in FIGS. 6A--6D) to a second pair
of hydraulic cylinders 174 and 176 also mounted on the mounting
block 144. Finally, crosshead 158 is connected through piston rods
178 to another pair of cylinders 180 and 182 also mounted on the
mounting block 144. Also mounted on the mounting block 144 is a
centrally located air cylinder 184 having a piston rod 186 (FIG.
6A) connected to a cup-shaped member 188 adapted to press against
the back face of the third crosshead 158.
The operation of the embodiment of FIGS. 4 and 5 can best be
understood by reference to FIGS. 6A--6D. In FIG. 6A, a tube T is
shown clamped by the clamping mechanism, schematically illustrated
at 134; while all of the crossheads 154, 156 and 158 are shown in
their retracted positions with the cup-shaped member 188 in
abutment with crosshead 158. The air cylinder 184 is usually
pressurized at all times, thereby applying a force against all of
the crossheads 154--158. However, with all of the crossheads
retracted as shown in FIG. 6A, for example, the air cylinder cannot
push them to the left, notwithstanding the fact that it is exerting
a mild force thereon. The reason for this can best be explained by
the hydraulic schematic shown in FIG. 6E. The cylinders 168 and 170
are connected to a pressure supply line 190 through a closed-center
valve 192 operated by means of solenoids 194 and 196. With a
closed-center valve of this type, and assuming that the valve is in
the neutral position shown in FIG. 6E, oil is trapped on either
side of the pistons within the cylinders 168 and 170. Hence, the
pistons are locked in place as is the crosshead 154. The cylinders
174 and 176, as well as cylinders 180 and 182, are controlled by
means of open-center valves 198 controlled by means of solenoids
200 and 202. In this case, the open-center valves 198 interconnect
the chambers on opposite sides of the pistons in cylinders 174 and
176 or cylinders 180 and 182. Hence, as long as the valves 198 are
in the neutral positions shown, the pistons and piston rods within
cylinders 174, 176, 180 and 182 can move more or less freely.
With this in mind, the operation of the system can now be described
with reference to FIGS. 6A--6D. As was mentioned above, all of the
crossheads 154, 156 and 158 are retracted at the beginning of a
pointing operation with a tube T gripped by the clamping mechanism
134 and the air cylinder 184 pressurized to exert a force on all of
the crossheads. By virtue of the fact that the cylinders 168 and
170 are controlled by the closed-center valve 192, the crosshead
154 is locked in position and restrains the crossheads 156 and
158.
A pointing operating begins by actuating valve 192 to pressurized
cylinders 168 and 170 and move the crosshead 154 to the left as
viewed in FIG. 6B, thereby forcing the die 160 over the end of the
tube. This elongates the tube slightly and decreases its diameter,
as was the case in FIGS. 3A--3D. By virtue of the fact that the
cylinder 184 is pressurized, the cup-shaped member 188 urges the
crossheads 156 and 158 to the left also and into engagement with
the end of the point being formed. That is, the die 162 on
crosshead 156 engages the end of the tube and restrains it from
moving offcenter by virtue of the more or less gentle pressure
exerted by the air cylinder 184.
After the crosshead 154 is moved to the left as viewed in FIG. 6B,
the cylinders 174 and 176 are pressurized, thereby forcing
crosshead 156 and its die 162 over the end of the tube T. At the
same time, the cup-shaped member 188 and air cylinder 184 exert
sufficient pressure on the crosshead 158 to cause its die 164 to
again engage the end of the point and restrain it from moving
offcenter. Finally, and as shown in FIG. 6D, the cylinders 180 and
182 are pressurized to force the crosshead 158 to the left whereby
its die 164 is forced over the end of the point. The cup-shaped
member 188 now receives the end of the point and, again, by virtue
of the pressure exerted by the air cylinder 184, restrains the end
of the point from moving offcenter. Following this, cylinders 168
and 170 are pressurized in the opposite direction to withdraw the
dies from the end of the formed tube. This forces crossheads 156
and 158 backwardly also with the oil returning to a reservoir
through open-center valves 198; while at the same time the
cup-shaped member 188 and piston within air cylinder 184 are forced
backwardly by virtue of the higher pressure exerted by the
hydraulic cylinders. When the crossheads are all back in their
retracted positions shown in FIG. 6A, the crosshead 154 locks them
in position, even though pressure is exerted by the air cylinder
184, by virtue of the closed-center valve 192 as explained above.
In the embodiment of FIGS. 4, 5 and 6A--6E, therefore, the end of
the point is at all times restrained in order that it cannot curve
or bow during the extrusion process.
In FIGS. 7, 8 and 9, another embodiment of the invention is shown
which does not employ multiple, concentric dies, but does employ an
air cylinder for the purpose of preventing bowing in the extruded
point. It again includes side members or channels 204 and 206 which
support, at one end, a clamping mechanism 208 and at the other end
a mounting block 210. Secured to the side members 204 and 206 are
upright angles 212; and extending between the angles 212 and the
mounting block 210 are columns or cylindrical guide rods 214 and
216 which carry, for reciprocating movement, a crosshead 218. The
crosshead 218, in turn, is connected through piston rods 220 and
222 to a pair of hydraulic cylinders 224 and 226, respectively.
Intermediate the cylinders 224 and 226 is an air cylinder 228
connected through piston rod 230 to a cup-shaped member 232,
similar to the cup-shaped member 188 in the embodiment of FIGS. 4,
5 and 6A--6E.
Mounted on the crosshead 218 is a rotary head or die holder 234.
The die holder 234 rotates about a central pin 236 which is
threaded into the crosshead 218. Circumferentially spaced around
the die holder 234 are slots 238, each slot 238 having a
semicircular seat 240 to receive a die 244. The dies 244, in turn,
are held within the slots 238 by means of springloaded balls 242
which permit the circular dies to pass into their slots but keep
them from falling out under the force of gravity. The rotary die
holder 234 may be provided with a handle 245 adapted to slidably
fit into bores 246 spaced around the periphery of the die holder
234.
With the arrangement of FIGS. 7 and 8, the centerline of a tube
being pointed is concentric with the uppermost die shown in FIG. 8.
That is, it lies in the same horizontal plane with the axes of the
columns 216. The operation of the pointer is similar to that
described in connection with FIGS. 6A--6E in that the cup-shaped
member 232, under the force of air cylinder 228, prevents the end
of the point from curving offcenter. However, the embodiment of the
invention shown in FIGS. 7 and 8 does not employ concentric dies.
Rather, a die is rotated into the uppermost position on the rotary
head 234; that die is forced over the end of the tube; the die is
retracted; and then the rotary head is rotated to the next, smaller
die where the pointing operation can be repeated. This type of
pointer is particularly adapted for use in applications where only
small reductions in the point need be taken as, for example, points
used for a bull block operation.
To accommodate tubes of different diameters, the clamping mechanism
208 is provided with a pair of octagonal inserts 250 and 252 which
fit into stationary and reciprocable clamp holding members 254 and
256, respectively, provided with seats which receive the inserts
250 and 252 (FIG. 9). Each of the faces of the octagonal inserts
250 and 252 is provided with a semicylindrical channel 262 which,
when mated with the corresponding channel in the other insert,
forms a cavity 264 for reception of a tube to be clamped. By
removing the inserts 250 and 252 and rotating them, it will be
readily appreciated that tubes of various diameters can be
accommodated by the clamp.
Although the invention has been shown in connection with certain
specific embodiments, it will be readily apparent to those skilled
in the art that various changes in form and arrangement of parts
may be made to suit requirements without departing from the spirit
and scope of the invention.
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