U.S. patent application number 12/106912 was filed with the patent office on 2008-10-23 for method and system for manufacture of a wire cage.
Invention is credited to Claudio Subacchi.
Application Number | 20080257445 12/106912 |
Document ID | / |
Family ID | 39636897 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080257445 |
Kind Code |
A1 |
Subacchi; Claudio |
October 23, 2008 |
Method And System For Manufacture Of A Wire Cage
Abstract
A wire cage making machine includes a pair of rod supporting
wheels decoupled from one another and capable of being rotated by
respective motors at different speeds and/or directions to control
the contour of a wire cage, such as twisting the rods. The machine
includes a carriage to which the wheels are mounted, with one of
the wheels maintained at a fixed position on the carriage and the
other wheel movable along rails of the carriage. A welding head is
positioned proximate the stationary wheel and is connected to the
carriage by a pivot arm that allows the welding head to be moved
closer to or farther away from the center of the stationary wheel.
The pivot arm allows the position of the welding head to be moved
in response to changes in radial positions of longitudinal rods
carried by the wheels and to which wire is welded, to join the rods
together to form a wire cage. The rods are held by clamps mounted
to spokes of the wheels. The radial position of the clamps of the
stationary wheel can be moved in real-time to change the diameter
of the wire cage.
Inventors: |
Subacchi; Claudio;
(Piacenza, IT) |
Correspondence
Address: |
BOYLE FREDRICKSON S.C.
840 North Plankinton Avenue
MILWAUKEE
WI
53203
US
|
Family ID: |
39636897 |
Appl. No.: |
12/106912 |
Filed: |
April 21, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60913166 |
Apr 20, 2007 |
|
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Current U.S.
Class: |
140/113 |
Current CPC
Class: |
B21F 27/124
20130101 |
Class at
Publication: |
140/113 |
International
Class: |
B21F 15/02 20060101
B21F015/02 |
Claims
1. An apparatus for manufacturing a wire cage, the apparatus
comprising: a first rotating member configured to support a
plurality of cage rods; a second rotating member configured to
support the plurality of cage rods, the second rotating member
spaced from the first rotating member and the plurality of cage
rods extending between the first rotating member and the second
rotating member; and a drive assembly that independently rotates
the first rotating member and the second rotating member.
2. The apparatus of claim 1 wherein the drive assembly rotates the
first rotating member and the second rotating member at different
rotational speeds to effectuate twisting of the plurality of cage
rods extending between the first rotating member and the second
rotating member.
3. The apparatus of claim 1 wherein the drive assembly comprises a
first drive motor coupled to the first rotating member to rotate
the first rotating member and a second drive motor coupled to the
second rotating member to rotate the second rotating member.
4. The apparatus of claim 1 further comprising a track along which
the second rotating member may be translated to define the spacing
between the first rotating member and the second rotating
member.
5. The apparatus of claim 1 further comprising a wire feed that
delivers wire to weld, in a spiral pattern, around the plurality of
cage rods.
6. The apparatus of claim 5 further comprising a welding assembly
to weld the wire to the plurality of cage rods, the welding
assembly including: a welding head secured to a pivot arm; and
means for effecting selective pivoting movement of the pivot arm to
control positioning of the linear welding head.
7. The apparatus of claim 6 wherein apparatus includes a frame, and
wherein the pivot arm is pivotably mounted to the frame.
8. The apparatus of claim 6 wherein the welding assembly comprises
a transformer that allows for maximum current transfer to the
wire.
9. The apparatus of claim 6 wherein the welding assembly welds the
wire to a cage rod at approximately 1000 Hz and at approximately
400 A current.
10. The apparatus of claim 1 wherein the cage rods are composed of
high carbon steel.
11. A method of manufacturing a welded wire structure, the method
comprising: securing a plurality of longitudinal steel rods to a
first wheel and a second wheel spaced from the first wheel;
independently rotating at least one of the first wheel and the
second wheel; and welding a circumferential wire to the plurality
of steel rods as the first and second wheels are rotated and the
second wheel is moved away from the first wheel.
12. The method of claim 11 wherein the step of rotating the first
and second wheels includes rotating the first wheel at a first
speed and rotating the second wheel at a second speed, different
from the first speed.
13. The method of claim 11 wherein the step of rotating the first
and second wheels includes rotating the first wheel in a first
direction and rotating the second wheel in a second direction,
different from the first direction.
14. The method of claim 11 further comprising changing the radial
position of the longitudinal steel rods as the second wheel is
moved away from the first wheel.
15. A welding system comprising: a linear welding head having a
copper contact; and a pair of hydraulic pistons connected to the
linear welding head to control positioning of the linear welding
head relative to a longitudinal rod and spiral wire used to form a
part of a reinforcing cage for a concrete structure.
16. The welding system of claim 15 wherein the copper contact is
composed of soft copper.
17. The welding system of claim 15 further comprising a spool of
wire that is controlled to present the spiral wire to the linear
welding head.
18. The welding system of claim 15 further comprising a transformer
that is connected to the copper contact in a manner that allows for
maximum current transfer to the spiral wire and a longitudinal
rod.
19. The welding system of claim 15 configured to weld at 1000 Hz
and a 400 A current.
20. The welding system of claim 15 mounted adjacent an assembly
that presents longitudinal rods to be weld to the spiral wire, the
assembly including: a first rotating member configured to support a
plurality of cage rods; a second rotating member configured to
support the plurality of cage rods, the second rotating member
spaced from the first rotating member and the plurality of cage
rods extending between the first rotating member and the second
rotating member; and a drive assembly that independently rotates
the first rotating member and the second rotating member to
effectuate orientation changes in the plurality of spinal rods as
defined between the first rotating member and the second rotating
member.
21. An apparatus for use with a wire cage making machine and
configured to change the radial spacing of longitudinal rods that
form part of a wire cage, the apparatus comprising: a guide coupled
to a wheel that holds the longitudinal rods and is rotated to
present the rods and connecting wire to a welding unit that welds
the connecting wire to the longitudinal rods, wherein the wheel
includes a central hub, an outer rim, and spokes extending between
the central hub and the outer rim; longitudinal rod clamps mounted
to the spokes; a mounting member movable along the guide; flexible
elongated drive members coupling the clamps to the mounting member;
and an actuator that moves the mounting member along the guide,
wherein movement of the mounting member changes the radial position
of the clamps relative to the central hub of the wheel.
22. The apparatus of claim 21 wherein the actuator includes a
cylinder coupled to the central hub and rotatable with the wheel
and a ram rotatable with the wheel and connected to the cylinder
and the chain mount.
23. The apparatus of claim 21 further comprising a post that
supports the guide and a bearing interconnected between the post
and the guide that allows the guide to rotate relative to the post
in response to rotation of the wheel.
24. The apparatus of claim 21 further comprising a sensor that
detects a position of the mounting member along the guide and
provides feedback to a controller that determines the radial
position of the clamps from the hub.
25. A wire cage making machine comprising: a carriage; a stationary
wheel mounted to the carriage; a movable wheel mounted to and
movable along the carriage; a welding unit for welding wire to
longitudinal rods carried by the stationary wheel and the movable
wheel, the welding unit having a welding head mounted to an arm;
and a bracket coupling the arm to the carriage, wherein the bracket
allows the arm to pivot so as to move the welding head in response
to changes in radial position of the longitudinal rods.
26. The wire cage making machine of claim 25 wherein a linear
welding head has a copper contact and a pair of hydraulic pistons
connected to the arm to control positioning of the linear welding
head relative to a longitudinal rod and wire.
27. The wire cage making machine of claim 25 wherein the welding
unit includes a pair of rollers and brushes to conduct welding
current from a power source to a longitudinal rod and the wire.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of U.S. Ser. No.
60/913,166, filed Apr. 20, 2007, the disclosure of which is
incorporated herein by reference.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] Wire cages are commonly used as the reinforcing structure
for concrete pipes and other cast concrete products. Typically, the
wire cages consist of a series of longitudinal steel rods
interconnected by a circumferential spiral wire that is welded to
the longitudinal rods. Wire cages are made using a machine composed
of a pair of wheels; one of which is stationary and the other of
which is movable. The wheels carry clamps that hold the rods as the
spiral wire is welded to the rods. The wheels are mechanically
coupled to one another by a drive shaft that is rotated by an
electric motor to synchronize rotation of the wheels to
incrementally present the steel rods and spiral wire to a welding
unit. More particularly, the electric motor spins the drive shaft,
which then through gears and a chain mounted on the outer edge of
both wheels, causes the wheels to rotate. These mechanical
connections can deteriorate over time, thereby causing
inconsistencies in the rotational velocity of the wheels and
ultimately defects in the finished wire cage.
[0003] Thus, in one aspect, the present invention is directed to a
wire cage forming machine in which the two wheels are not
mechanically coupled to one another by a drive shaft. Each wheel is
rotated by a separate drive motor, and feedback from the drive
motors is used to control the rotational speed of the wheels. For
instance, the motors may be controlled by a programmable logic
controller (PLC) and arranged in a master-slave arrangement. The
rotational speed of the movable wheel may thus be controlled to
match the rotational speed of the stationary wheel.
[0004] With a conventional wire cage making machine, the wheels are
rotated at substantially same speed by the drive shaft. As such,
the longitudinal rods are uniformly aligned along the length of the
wire cage. That is, the rods are not only parallel with one another
along the length of the wire cage, but the angular position of the
rods relative to the center axis of the wire cage is constant along
the entire length of the rods. This can be problematic for wire
cages used in the concrete pipe industry, as the concrete pipe
manufacturing machinery can twist the wire cage while the concrete
is being formed around the wire cage. This twisting may cause
torsional stress in the wire cage, and once the concrete pipe is
released from its mold the wire cage has a tendency to straighten
from the twisted state back to its original configuration. This can
cause cracks to form in the concrete pipe. Thus, it may be
desirable to intentionally twist the rods of the wire cage during
the cage making process, so as to counteract the rotational forces
applied to the wire cage by the pipe-making equipment during
production of the concrete pipe.
[0005] Twisting the rods using a conventional cage making machine
is generally not possible given the mechanical coupling of the
wheels. The present invention, however discloses decoupled wheels
that are separately driven by respective electric motors. The
electric motors can thus be controlled to rotate the wheels at
different speeds or in opposite directions to twist the rods during
production of the wire cage.
[0006] In accordance with another aspect, the invention discloses a
friction wheel drive for rotating the wheels. The friction wheel
drive reduces vibrations in the cage making machine and therefore
provides for smoother operation at higher rotational speeds. In
addition, it is believed that the friction drive is more reliable
and less prone to premature mechanical failure.
[0007] The wheels of a conventional wire cage making machine
include central hubs and spokes extending from the hubs to outer
annular rims. Each spoke carriers a rod clamp capable of holding a
longitudinal rod at two different radial positions. Thus, the wire
cage making machine can make a wire cage having one of two
diameters. A single wire cage having certain lengths at one
diameter and other lengths at a different diameter may be made by
manually changing the position in the clamp where the rods are
held, but this is a labor intensive process and, as such, can be
costly.
[0008] In accordance with another aspect, the present invention
discloses an apparatus capable of adjusting the radial spacing of
the longitudinal rods without requiring manual repositioning of the
rods in their spoke-mounted clamps. Moreover, the apparatus allows
the radial spacing to be changed in real-time. In general, the
apparatus includes a chain mount slidable along a guide tube. An
actuator pushes or pulls the chain mount toward or away from the
hub of the stationary wheel. As the chain mount is translated along
the guide tube, the radial position of the rod clamps, which are
connected to the chain mount by chains, is varied. The radial
position of the clamps can be changed independent of the rotation
of the stationary wheel. Accordingly, the apparatus of the present
invention may be used to produce a wire cage having any desired
diameter. In addition, the diameter of the wire cage can be varied
as the cage is being produced, the provide a cage having any
desired profile.
[0009] Various other features, objects and advantages of the
invention will be made apparent from the following description
taken together with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The drawings illustrate the best mode presently contemplated
of carrying out the invention.
[0011] In the drawings:
[0012] FIG. 1 is an isometric view of a wire cage making machine
having a stationary wheel and a movable wheel which are separately
and independently driven by respective drive motors, which allows
the wheels to be rotated at different speeds and/or different
directions, according to one aspect of the invention;
[0013] FIG. 2 is a top plan view of the wire cage making machine of
FIG. 1;
[0014] FIG. 3 is a front end elevation view of the stationary wheel
incorporated in the wire cage making machine of FIG. 1;
[0015] FIG. 4 is a front end view of the movable wheel incorporated
in the wire cage making machine of FIG. 1;
[0016] FIG. 5 is a front isometric view of the stationary wheel end
of the wire cage making machine of FIG. 1, showing a welding head
mounted to a pivot arm proximate the stationary wheel, according to
one aspect of the invention;
[0017] FIG. 6 is a schematic of a welding unit incorporated in the
wire cage making machine of FIG. 1, according to one aspect of the
invention;
[0018] FIG. 7A is a simplified section view of a cage diameter
control system incorporated in the wire cage making machine of FIG.
1, coupled to the stationary wheel and having a chain mount
positioned at a first linear position along a guide tube to
position rod clamps mounted to spokes of the stationary wheel at a
first radial position;
[0019] FIG. 7B is a simplified section view of the cage diameter
control system similar to FIG. 7B, with the chain mount at a second
linear position along the guide tub to position the rod clamps at a
second radial position along the spokes of the stationary
wheel;
[0020] FIG. 8 is a schematic diagram of a wire cage produced using
the wire cage making machine of FIG. 1, with uniformly aligned
longitudinal rods;
[0021] FIG. 9 is a schematic diagram of a another wire cage
produced using the wire cage making machine of FIG. 1, with twisted
longitudinal rods; and
[0022] FIG. 10 is a schematic diagram of a wire cage produced using
the wire cage making machine of FIG. 1, with twisted longitudinal
rods and variations in cage diameter along the length of the wire
cage.
DETAILED DESCRIPTION OF THE INVENTION
[0023] This invention relates to a system and method for making
wire cages that may be particularly useful for reinforcing concrete
pipe or other tubular concrete structures. A wire cage generally
consists of a series of longitudinal rods interconnected by a
circumferential or spiral rod or wire that is welded to the
longitudinal rods at each point at which the circumferential rod or
wire intersects the longitudinal rods. A wire cage making machine
10 is shown in FIG. 1 and is composed of four general components or
systems: a rod support frame or carriage 12, a cage diameter
control system 14, a welding unit 16, and a control station 18.
Each of these systems will be described in greater detail below,
but generally these systems provide increased flexibility in
defining the contour of a wire cage. It is noted that a wire cage
making machine may have additional components or systems not
specifically described herein.
Rod Support Carriage
[0024] Referring to FIGS. 1, 2 and 4, the rod support carriage 12
includes a stationary wheel 20 and a movable wheel 22 supported by
a frame 24. The frame 24 includes a pair of rails 26, 28 that
support the movable wheel 22 and house a pair of racks 30, 32,
respectively, along which the movable wheel 22 may be translated to
pull longitudinal rods through the stationary wheel 20, as will be
explained further below. The frame further includes a base 34 that
supports the stationary wheel 20. The movable wheel 22 is
translated along the racks 30, 32 by a drive motor 36 that drives a
pair of pinions 38, 40 through a drive shaft 41, along the pair of
racks 30, 32. In operation, longitudinal rods are fed through the
stationary wheel 20 and fastened to the movable wheel 22. During
the cage making process, the movable wheel 22 is moved away from
the stationary wheel 20 by operation of the drive motor 36 rotating
the pinions 38, 40 to move along the racks 30, 32, until a desired
cage length is reached. It should be noted that the carriage 12 may
support more than the one movable wheel shown in the figures.
[0025] The movable wheel 22 is comprised of an annular rim 42, a
hub 44, and a series of radially spaced spokes 46 connected between
the rim 42 and the hub 44. A cover 48 generally encloses a bottom
half of the annular rim 42 to prevent unintended contact with the
movable wheel 22. Each spoke 46 carries a rod clamp 50, each of
which holds the end of a respective longitudinal rod during the
cage making process. The rod clamps 50 also hold their respective
rods as the wheel is rotated about a central axis 52 extending
through the hub 44.
[0026] The movable wheel 22 is supported on a carriage 53, to which
drive motor 36 is mounted. The movable wheel 22 is supported for
rotation on carriage 53 by a central axle oriented along axis 52,
which is rotatably mounted within a suitable bearing 55 that is
secured to carriage 53.
[0027] The movable wheel 22 may be rotated in either a clockwise or
counterclockwise direction by a drive motor 54, which drives a
roller 56. The drive roller 56 frictionally engages and drives the
annular rim 42 in a controlled manner, so as to impart rotation to
wheel 22 in response to operation of drive motor 54. It is
understood that any other satisfactory type of driving engagement
between drive motor 54 and rim 42 may be employed, such as a gear
or chain drive.
[0028] With additional reference to FIG. 3, the stationary wheel 20
is similar in construction to the movable wheel 22. The stationary
wheel 20 includes an annular rim 58, a center hub 60 aligned with
axis 52, and a series of spokes 62 that extend between, and are
connected to, the hub 60 and the rim 58. Each spoke 62 also carries
a rod clamp 64 that retains a respective longitudinal rod but does
so in a manner that allows the rods to be pulled through the wheel
20 as the movable wheel 22 is moved.
[0029] The stationary wheel 20 is also rotatable about the central
axis 52 by a drive motor 65, which rotates a drive roller 66. An
annular ring 59 is mounted to the annular rim 58, and the drive
roller is engaged with ring 59 to frictionally drive or rotate the
annular rim 58. Alternatively, it is understood that any other
satisfactory type of driving engagement between drive motor 65 and
ring 59 or rim 58 may be employed, such as a gear or chain drive.
The stationary wheel 20 is partially encased by a generally
arch-shaped bulkhead 68. Rollers 70, 72, and 74 are mounted to an
inside surface of the bulkhead 68 and ride along ring 59. Rollers
70, 72, and 74 function to stabilize and guide movement of the
wheel 20 as it is rotated.
[0030] In one representative embodiment, the stationary wheel 20
and the movable wheel 22 are each frictionally driven by their
respective drive motors and rollers. This is in contrast to gear
and chain drive systems that are typically employed to rotationally
drive the wheels. Frictionally driving the wheels 20, 22 reduces
vibrations thereby providing smoother operation at higher
rotational speeds. The drive motors are controlled by a
programmable logic controller (PLC), with drive motor 54 used as a
slave motor and drive motor 65 used as a master motor. In this
configuration, the stationary wheel 20 will act as the master and
the rotational velocity of wheel 20 will be calculated by the PLC.
The velocity of the movable wheel 22 is then calculated and through
a feedback system the rotational velocity of movable wheel 22 is
correlated to the rotational velocity of the stationary wheel 20.
In an application in which a cage having straight longitudinal
rods, the rotational velocity of movable wheel 22 is made to match
that of stationary wheel 20. This feedback system also allows the
slave motor 54 to rotate the wheel 22 at an advanced or retarded
pace relative to the stationary wheel 20, to provide the
longitudinal rods with a spiral or zig-zag configuration, when
desired. This provides considerable benefits and flexibility in the
manufacture of wire cages for various applications.
[0031] In the illustrated embodiment, a drive shaft does not extend
between the wheels (in contrast to known prior art). However, it is
understood that the wheels could be connected to a common drive
shaft that is rotated by a single drive motor, e.g., drive motor 65
when it is desired that the wheels be rotated in unison. For such
an embodiment, a clutch or similar device could be used to
disconnect the wheels from the drive shaft when it is desired to
separately rotate the wheels.
Welding Unit
[0032] As shown in FIGS. 1, 3, and 5, the welding unit 16 is
positioned proximate the stationary wheel 20 and generally includes
a power unit 76 and a welding head 78. The welding head 78 is
mounted to an arm 80 that is pivotably attached to the frame or
carriage 12, such as rail 28. More particularly, the arm 80 is
pivotably supported by a pivot pin that is engaged with a bracket
82 attached to the rail 28. The bracket 82 allows the arm 80 to
pivot about the pivot pin to accommodate for variations in the
diameter of the cage, as will be explained further below.
[0033] The power unit 76 is supported by a stanchion 84 to which a
pair of cylinders 86, 88 are mounted. The cylinders 86, 88 include
rams 90, 92, respectively, that are coupled to the arm 80. When the
rams 90, 92 are extended, the arm 80, and thus the welding head 78,
is pivoted about bracket 82 to move welding head 78 inwardly.
Likewise, when the rams 90, 92 are retracted, the arm 80, and thus
the welding head 78, is pivoted about bracket 82 to move welding
head 78 outwardly. In one embodiment, the cylinders are hydraulic
cylinders, but other types of cylinders or actuators may be used,
such as pneumatic cylinders, or similar mechanized devices, such as
screw drives or other linear actuators.
[0034] The welding head 78 is designed to spot weld wire
circumferentially around the longitudinal rods extending between
the wheels 20, 22 that form the body of the wire cage. The welded
circumferential wire effectively joins the longitudinal rods
together to form the cage. In this regard, the circumferential wire
is fed from a wire supply 94, FIG. 1, to the welding head 78. The
circumferential wire is guided by an arcuate guide channel 96
supported by table 98, which may be integrally formed with the
frame or carriage 12. The circumferential wire is fed through a eye
99, and is held against the guide wall by rollers 100 that are
supported by the table 98. The wire is then threaded through
rollers 102 and a pinch 104. From the pinch 104, the wire is passed
under rollers 106, 108 that are mounted to arm 80, and is then fed
to the welding head 78 for welding to the longitudinal rods.
[0035] During the cage making process, the circumferential wire is
presented to the welding head 78, which spot welds the
circumferential wire to the longitudinal rods extending through the
stationary wheel 20 and held by the movable wheel 22 as the
longitudinal rods are rotated by the wheels 20, 22 and moved
axially away from the stationary wheel 22 by movement of movable
wheel 20. The spot welding operation is carried out as the
stationary and movable wheels 20, 22 are rotated so that the
longitudinal rods are successively presented to the welding head 78
along with the circumferential rod. The constant rotation of the
stationary wheel 20 ensures that the circumferential wire is
maintained taut against the longitudinal rods, so that a good weld
can be made. The welding head 78 may then weld the wire to the next
longitudinal rod. The movement of movable wheel 22 along the rails
26, 28 as the welding operation is taking place provides the
circumferential wire with a spiral configuration a around the
longitudinal rods.
[0036] In one embodiment, the welding unit 16 welds wire to the
steel rods at 1000 Hz with a 400 A current. In this regard, the
welding unit 16 offers a number of advantages over the welding
machines conventionally used in cage manufacturing. Specifically,
the welding unit creates less slag and spark while welding, along
with creating a stronger weld that is less tempered than the weld
produced by conventional welding units. Additionally, weld time is
less with welding unit 16 compared to conventional welding units,
which yields reduced cage production time that can be realized in
increased productivity for the manufacturer. The welding unit 16
also provides less tempering of the steel rods. This allows steel
to be used which contains more carbon than can be used with
traditional welding units. Moreover, high carbon steel wire is
generally less expensive than low carbon steel wire thereby
providing a decrease in manufacturing costs.
TABLE-US-00001 Weld Welding Unit Wire Size Time Ramp Time Welding
Current Proposed 8 mm wire 30 ms 10 ms 10 kA 1000 Hz Conventional 8
mm wire 60 ms -- 15 kA 50 or 60 Hz
[0037] As shown in the table above, the weld time of welding unit
16 may be half the time of a conventional welding unit. This
provides extra time for the welding unit 16 to create a ramp effect
using pulse width modulation in order to allow the steel to cool
relatively slowly over an additional 10 ms period of time. During
this cooling process the carbon contained in the steel is kept
misaligned, which permits the steel to retain its malleable
properties. This is in contrast to conventional manufacturing
techniques which utilize multiple heating and cooling cycles for a
single weld, which may result in steel that is tempered, where the
carbon molecules in the steel align with one another and create
very hard and brittle portions near the weld area thereby reducing
the strength of the overall wire cage.
[0038] In one embodiment, the welding operation carried out by the
welding head 78 uses a pair of rollers and brushes to transfer
electrical current to the wire and longitudinal rods, such as
illustrated in FIGS. 3 and 5. However, in another embodiment, which
is schematically illustrated in FIG. 6, the welding head 78 has a
copper welding contact 110 that forms the welding arc with the
steel rods 112 during welding of wire 114 to the longitudinal steel
rods 112 without the aforementioned rollers and brushes, which tend
to create relatively large resistance that must be overcome. The
welding head 78 utilizes two hydraulic cylinders 116, 118 to
maintain proper position of the copper contact 110. Copper contact
110, in one embodiment, is much smaller than that used in
conventional welding heads, which greatly reduces the weight and
cost of the head. In addition, the welding unit 78 uses a linear
welding head which increases the flow of current to the copper
contact and steel rods resulting in a stronger weld.
[0039] The hydraulic cylinders 116, 118 may be controlled to
minimize the wear of the copper contact as it contacts the wire and
steel rods. The use of a hydraulic system instead of a pneumatic
system allows for less expensive "soft copper" to be used as the
contact for the welding head rather than "hard copper". "Soft
copper" is less expensive than the "hard" copper alloy which is
typically used to make the contacts.
[0040] As noted above, a linear welding head may be used rather
than rotating copper wheels and brushes. This may provide greater
efficiency in the welding circuit as a result in the decrease in
the resistance between the connection of the copper contact 110 and
the transmission wires 120, which are used to transmit the current
from the welding transformer 122 to the contact 110. When
transmitting 15 kilo-amperes of current, for example, a change of
resistance of even one ohm can make a very large difference in
efficiency. With a linear welding head the connection between the
welding transformer 122 and the copper contact 110 is a constant
contact and has a very low resistance compared to copper brushes
contacting the spinning copper wheels.
Rod Radial Spacing Control
[0041] Referring again to FIGS. 1 and 2, and with further reference
to FIGS. 7A and 7B, the rod radial spacing control system 14
includes a guide tube 124 connected at one end to the hub 60 of the
stationary wheel 20 and connected at an opposite end to a post 126.
The guide tube 124 is designed to rotate with rotation of the
stationary wheel 20. In this regard, the guide tube 124 is fixed to
the hub 60 of the stationary wheel 20 and is coupled to the post
126 through a bearing 128.
[0042] A chain mount 130 is mounted to the guide tube 124 and
rotates with the guide tube 124. A series of chain guides 136 are
mounted to a forward face of the chain mount 130. The number of
chain guides 136 is equal to the number of rod clamps 64 carried by
the spokes 62 of the wheel 20. Chain guides 138, 140, which are in
the form of sprockets, are secured to a rear surface of a hub mount
143 that is coupled to the hub 60 of the wheel 20. Chain guides 138
are spaced inwardly of chain guides 140. An additional set of chain
guides 142, which are also in the form of sprockets, are mounted to
the spokes 62 of the wheel. More particularly, a flange 144 is
mounted to each of the spokes 62 and the chain guides 142 are
coupled to the flanges 144.
[0043] Two respective chains 146, 148 are associated with each
spoke 62 of the stationary wheel 20. Chain 146 has a first end 150
coupled to a bracket 152 to which clamp 64 is connected and a
second end 154 connected to a carrier bracket 156. A cylinder 132
is housed within the guide tube 124 and includes a ram 134 that is
coupled to the carrier bracket 156 through a slide block 157. The
ram 134 is preferably fixed to the slide block 157 so as to rotate
with the slide block 157. However, the cylinder 132 is arranged
within the interior of guide tube 124 so as not to rotate along
with guide tube 124. To this end, suitable bearings may be
positioned between the cylinder 132 and the inner wall of guide
tube 124, so that cylinder 132 does not rotate.
[0044] When the ram 134 is retracted, the carrier bracket 156 is
moved along the guide tube 124 and away from the wheel 20.
Similarly, when the ram 134 is extended the carrier bracket 156
moves toward the wheel 20.
[0045] Chain 148 has a first end 158 that is coupled to the clamp
bracket 152 and a second end 160 that is coupled to the carrier
bracket 156. When the ram 134 is extended, the carrier bracket 156
is pushed toward wheel 20 which results in the chains 146, 148
moving in a clockwise direction (in the illustrated figure). As the
clamp 64 is coupled to chains 146, 148, the clamp 64 will move in
response to movement of the carrier bracket 156. Thus, when the ram
134 is extended, the clamps 64 are pushed away from the hub 60 by
their respective chains 146, 148. Each clamp 64 carries a rod guide
tube 162 through which the longitudinal rods extend. As such, the
rods are pushed away from the hub 60 as the ram 134 is
extended.
[0046] Conversely, when the ram 134 is retracted the ram 134 forces
the carrier bracket 156 away from the hub 60. As a result, chains
146, 148 are pulled in a counterclockwise direction. Each clamp 64
is thus moved toward the hub 60 to decrease the distance of each
rod from the hub 60 decreasing the diameter of the wire cage. This
is particularly evident by comparing FIGS. 7A and 7B. FIG. 7A shows
the clamps 64 at a decreased radial distance resulting from
retraction of the ram 134, and FIG. 7B shows the clamps at an
increased radial distance resulting from extension of the ram
134.
[0047] A linear position sensor is used to detect the linear
position of the ram 134 and provide a corresponding signal to the
control station 18, which may include a computer or similar
processor for determining the radial position of the clamps 64 from
the position of the ram and move the welding head described above
accordingly. Representatively, the linear position sensor may be a
magnetoresistive transducer-type position sensor such as is
available from Gefran under its model number IK1A, although it is
understood that any other satisfactory type of position sensor may
be employed.
Control Station
[0048] The control station 18 can be of conventional design and, as
such, includes various operator input controls and system
monitoring devices including dials, meters, and other displays. The
control station 18 includes a computer (not shown) or other
processor to effectuate operator control of the cage making process
including, but not limited to automated control of the various
components of the cage making machine 10 such as those described
herein. In one embodiment, the control station 18 includes controls
that allow an operator to interface with the rod spacing control
components to change the diameter of a wire cage, or portions
thereof, in real-time. The welding unit 16 can also be controlled,
either manually or in an automated fashion, to respond to changes
in the spacing of the longitudinal rods so that welding head is
suitably pivoted toward or away from the longitudinal rods.
Additionally, the control station allows an operator to
interactively control the rotational speed of each wheel 20, 22 or
execute a stored program that independently controls the rotational
speed of each wheel 20, 22 which may include driving the wheels 20,
22 to rotate at different speeds or in different directions.
Exemplary Wire Cage Contours
[0049] As illustrated in FIGS. 8-10, the present invention allows
flexibility in the contour of a wire cage. FIG. 8 shows a schematic
for a wire cage 164 made with wheel 20 and 22 being rotated at the
same velocity. The wire cage 164 is generally cylindrical in shape
and is defined by a number of longitudinal steel rods 166 joined
together by a circumferential wire 168. The circumferential wire
168 has a generally spiral or helical shape which occurs by moving
the movable wheel 22 away from wheel 20 as the wheels 20, 22 are
rotated. FIG. 9 shows a wire cage 164(a) in which the longitudinal
steel rods 166(a) are angled from end-to-end. The diameter of the
wire cage 164(a) is uniform along the length of the wire cage
164(a). The angling of the rods 166(a) is created by rotating the
wheels 20, 22 at different speeds. The wire cage 164(a) is
advantageous in countering the torsional stresses placed on the
wire cage during concrete pipe formation. More particularly, the
twist in the longitudinal rods may be made to oppose the twist
generated by the concrete pipe manufacturing process.
[0050] FIG. 10 shows a wire cage 164(b) in which the longitudinal
rods 166(b) are angled and the radial spacing of the rods is not
uniform along the length of the cage 164(b). As noted above, the
rods can be twisted by rotating the wheels 20, 22 at different
speeds and/or directions. A radial distance of the rods 166(b) from
the center axis of the cage 164(b) can be achieved by extending and
retracting the ram 134 so that the position of the rods along their
respective spokes varies during the cage making process. It is
appreciated that contours and shapes other than those shown in
FIGS. 8-10 may be achieved through control of wheel rotational
speed, wheel translation speed, and translation of the rod
clamps.
[0051] Various alternatives and embodiments are contemplated as
being within the scope of the following claims particularly
pointing out and distinctly claiming the subject matter regarded as
the invention.
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