Note: Descriptions are shown in the official language in which they were submitted.
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
1
INFRARED WELDER
BACKGROUND OF THE INVENTION
[0001] This invention relates to devices for welding thermoplastic parts
by generating and aiming infrared energy.
[0002] Heat welding can be used to join two or more laminar plastic
parts together at discrete points. The discrete points can be at points
between layered parts, or at points along edges of the parts, or where the
two parts abut one another. This process is often used to join overlying parts
of automotive door panels.
[0003] Known methods include the use of lasers and ultrasonics.
Lasers provide a focused beam of light, but are expensive, and there are
dangers associated with laser radiation. Personnel working with lasers
usually require a laser radiation shield which adds further expense to the
operation of a laser system. Lasers also generate a substantial amount of
heat at the laser diode. This heat must be removed, and is therefore not
available at the point of welding.
[0004] Welding thermoplastic parts and plunge sealing film and fabric
materials by ultrasonic energy is well known. Generally, the workpiece is
supported on an anvil. An electroacoustic transducer coupled to a horn
dimensioned to be resonant for high frequency vibrations of predetermined
frequency is brought into forced engagement with the workpiece for a fixed
time interval or an interval which may be determined by process variables
such as,energy transfer or horn travel distance. When the horn is rendered
resonant, ultrasonic energy is transmitted to the workpiece to soften the
thermoplastic material of the workpiece. Upon cessation of the flow of
ultrasonic energy, the softened and flowed material rigidifies, thereby
establishing a bond or a weld. As used in this disclosure, the term
"ultrasonic" refers to vibrations having a frequency ranging generally
between about 10 KHz to about 100 KHz.
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
2
[0005] Generally, it is recognized that the ultrasonic power transmitted
to the thermoplastic parts is dependent on four parameters: namely, the
frequency of the electroacoustic transducer, the force or clamping pressures
applied to the thermoplastic parts by the horn, the motional amplitude of the
horn as it transmits the energy to the thermoplastic parts and the duration of
the energy transfer. It will be appreciated that there are other parameters
which can affect an ultrasonic weld as well. For example, the trigger force,
i.e., the force between the horn and the thermoplastic part below which no
ultrasonic energy is initially applied, the feed or down speed of the horn,
and
the time during which power is increased or decreased may all affect the
weld. In addition, ultrasonic methods heat up larger areas, and require more
intimate contact between parts to be joined.
[0006] It is therefore desirable to provide a welding device for
thermoplastics that is energy efficient and that is simple and compact in
construction, and which overcomes the problems associated with prior
devices.
SUMMARY OF THE INVENTION
[0007] The present invention provides a welding apparatus for joining
thermoplastic parts. The invention includes an energy source for generating
infrared energy, and an energy directing means for collecting and aiming or
directing the infrared energy to a spot on an adjacent thermoplastic part or
combination of parts. The apparatus forms a small spot on the exposed and
underlying parts to soften and fuse them together in a localized fashion.
[0008] A preferred embodiment utilizes at least one broadband
incandescent lamp as the infrared energy source. This lamp is preferably a
halogen lamp. The energy directing function can be performed by one or
more reflectors which are preferably gold plated to provide a preferentially
high reflectivity of the infrared radiation, thus increasing the percentage of
total energy produced reaching the spot to be welded.
[0009] The illustrative embodiments hereinafter described are
packaged in generally cylindrical form with a cylindrical body which houses
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
3
one or more lamps and one or more reflectors which direct infrared energy
out through an aperture. The aperture may be formed in an endcap which is
brought into proximity with the workpieces when welding is to be performed.
The apparatus may also include a spacer that provides for placing the welder
the correct distance from,the surface or surfaces to be welded.
[0010] In an alternative embodiment, the apparatus includes two
reflectors. The first reflector is disposed in surrounding relationship to the
incandescent lamp, and directs the energy to a second reflector. The
second reflector then redirects the infrared energy through the
aforementioned aperture. The two reflector design provides for easier
access to the incandescent lamps or lamps in the body of the device.
(0011] In a still further alternative embodiment, the apparatus includes
a light pipe which acts as an extension of the end cap to provide greater
control in directing the radiant energy. The extension also allows for the
concentration of energy in areas, such as depressions, which are difficult to
reach.
[0012] In a still further alternate embodiment, the apparatus includes
fiber optic cables for directing and focusing the infrared energy. The fiber
optic cables are arrayed to direct all energy exiting the cables to a single
spot.
[0013] Other objects, advantages and applications of the present
invention are described in the following specification which is to be read in
conjunction with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0014] The description herein makes reference to the accompanying
drawing wherein like reference numerals refer to like parts throughout the
several views, and wherein:
[0015] Figure 1 is a side elevation view of an infrared welder according
to a first embodiment of the invention;
[0016] Figure 2 is a cross-sectional view taken along line 2-2 of Figure
1;
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
4
[0017] Figure 3 is a side elevation view of a secondary reflector in the
infrared welder of Figures 1 and 2;
[0018] Figure 4 is an exploded view of the infrared welder of Figures 1
and 2;
[0019] Figure 5 is a view of the body assembly portion of the infrared .
welder of Figures 1 and 2;
[0020] Figure 6 is a side view of a second embodiment of the infrared
welder according to the present invention;
[0021 ] Figure 7 is a side view of an alternate embodiment of the
infrared welder according to the present invention;
Figure 8 is a schematic view of an infrared welder of the
present invention with an ellipsoidal primary reflector and a light pipe;
[0022] Figure 9 is a partial side view of an infrared welder according to
another embodiment of the invention;
[0023] Figure 10 is a cross-sectional view taken along line 10-10 of
Figure 9;
[0024] Figure 11 is a schematic view of an infrared welder using fiber
optic cables to focus the infrared energy;
[0025] Figure 12 is a schematic view of an infrared welder with an
internal press attached; and
[0026] Figure 13 is a schematic view of an infrared welder with an
external press attached.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] Referring to Figure 1, an infrared welder 10 generates energy
and focuses infrared energy onto two overlying thermoplastic parts 12, 14 to
join the two parts 12, 14 together in a localized area or spot. The energy
softens the plastic parts 12, 14 in a localized region where the parts 12, 14
overlie one another. The softened regions of the parts 12, 14 fuse when the
plastic resolidifies and creates a bond to secure the first and second plastic
parts 12, 14 together. A hole 16 is preformed in part 14 to allow energy to
reach the underlying part 12. This is typically needed only where the
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
material of the upper layer (part 14) is relatively opaque due to thickness
and/or color.
[0028] The infrared welding apparatus 10 includes a hollow cylindrical
body 20 and a reflector assembly 22. The assembly 22 includes a primary
reflector 24 with a central aperture. The central aperture receives an
incandescent lamp 26 which acts as an energy source. A 100 watt halogen
lamp is preferred for typical applications, such as the spot welding of
automotive door panels. As shown in Figure 2, the assembly 22 has a
circular configuration, wherein the lamp 26 is positioned in the center of the
assembly 22. A parabolic primary reflector 24 surrounds the lamp 26 and
directs radiant energy emitted by the lamp 26 in a generally axial direction.
An end cap 28 is attached to the body 20 so as to be axially contiguous to
the primary reflector 24 and defines a secondary reflector 30 with a central
aperture 32 to serve as an axial outlet for the infrared energy. The
secondary reflector 30 captures the radiant energy from the primary reflector
24 and, because of its shallow angles, redirects the radiant energy through
the aperture 32 to a point outside the apparatus 10. The net effect is one of
concentrating and aiming the energy to the spot where welding is to be done.
[0029] As shown in Figure 3, the lower end of the end cap 28 forms
the secondary reflector 30 and has an axis of symmetry 34 with the central
aperture 32 formed at the vertex of the end cap 28. A collar 36 extends
upwardly from the secondary reflector 30 and has an annular shoulder 38
immediately adjacent to the secondary reflector 30. The collar 36 fits over
the lower portion of the body 20, and is sized to fit snugly onto the body 20
for holding the reflector assembly 22 in position in the body 20. The primary
reflector 24 of the reflector assembly 22 rests on the shoulder 38 of the end
cap 28 when the apparatus 10 is assembled.
(0030] The secondary reflector 30 is a surface of rotation with a
curved shape designed to collect the radiation from the incandescent lamp
26 and the collimated radiation from the primary reflector 24 and direct the
radiation through the aperture 32 and to a point outside the apparatus. In a
preferred embodiment, the shape of the secondary reflector 30 is an off-axis
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
6
parabola of revolution. The shape is also known as a Wnston cone, or
compound parabolic concentrator (CPC), and is designed to maximize
collection of incoming radiation within some field of view. This is a non-
imaging light concentrator designed to funnel all wavelengths directed from
the primary reflector 24 and the lamp 26 through the aperture 32. The
design maximizes the collection of incoming radiation by allowing off axis
rays of light to make at least one bounce off the secondary reflector 30
before passing out the aperture 32.
[0031 ] As a design variation on the CPC, the secondary reflector 30
can also be formed as a frustum. The frustum being a truncated cone has a
larger end sized to fit over the end of the primary reflector 24. The smaller
end of the frustum provides the aperture 32 through which the radiant energy
is directed.
[0032] The welding apparatus 10 is shown in an exploded view in
Figure 4. The apparatus 10 is comprised of three sub-units; the body 20, the
reflector assembly 22, and the end cap 28. The reflector assembly 22
includes the primary reflector 24, the incandescent lamp 26, the lamp holder
40, and lamp holder electrical contacts.
[0033] In the apparatus 10 it was found that a part was needed for
firmly holding the lamp 26, and to provide for positioning and orientation of
the lamp 26. As such, the lamp holder 40 was developed for the apparatus
10. In addition, the lamp holder 40 provides for good electrical connection
between the leads from the lamp 26 to the electrical connectors 42.
[0034] The lamp holder 40 includes a circuit stamp 44 positioned
between a first lamp holder part 46 and second lamp holder part 48. The
lamp holder parts 46, 48 are fabricated from a high temperature plastic
formed with apertures for admitting electrical leads for contact with the
circuit
stamp 44. The lamp holder 40 is made from three separate pieces, but in
the alternative can be formed as a unitary piece.
[0035] The leads from the lamp 26 are inserted into apertures in the
lamp holder 40 and are held firmly. The lamp holder 40 is positioned on the
end of the reflector assembly 22 away from the primary reflector 24. The
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
7
lamp holder 40 holds the lamp 26 such that the lamp filament is positioned
substantially at a focal point of the primary reflector 24. Electrical
connectors
42 are inserted into the lamp holder 40 on the side opposite from the lamp
26. The reflector assembly 22 when assembled with the lamp 26 and lamp
holder 40 is shown in Figure 5. .
[0036] The body 20 when assembled provides for the necessary
electrical connection to the lamp 26. The body 20, as shown in Figure 4, is a
generally cylindrical unit with a hollow bore through the length of the body
20
having a first and second end. The body includes a cylindrical bore having a
receptacle region 50 at the first end sized to receive the reflector assembly
22. The body 20 includes a detent pin 52 for mating with a detent 54 in the
reflector assembly 22. The detent pin 52 limits the depth the reflector
assembly 22 is inserted into the body 20, and orients the reflector assembly
22 to a desired position within the body 20. The detent pin 52 is inserted
through a hole that extends through the wall of the body 20 to the interior
bore.
[0037] The body 20 includes an aperture for affixing an air fitting 56 to
the body 20. The air fitting 56 provides for attachment to an air source. The
air provided via the air fitting 56 is used for cooling the lamp 26 and for
providing cooling of the welded plastic following heating by the infrared
welder. The air flows through the bore in the body 20, through air apertures
in the lamp holder 40, and around the lamp 26. The air enters the chamber
ericompassed by the primary 24 and secondary 30 reflectors and exits pores
58 through the secondary reflectors 30 in the end cap 28. The pores 58 are
added to the end cap 28 to permit the egress of the air when the aperture 32
is blocked by the object being welded. The body 20 includes a cover 60 for
sealing the second end of the body 20. The cover 60 prevents air from
exiting the second end of the body 20. Optionally, a pneumatic cylinder (not
shown) may be attached for the purpose of driving a press 80 used for
forcing plastic pieces together.
[0038] The body 20 has a circumferential detent wherein an O-ring 62
is positioned. The O-ring 62 mates with a complementary detent situated in
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
8
the collar 36 of the end cap 28. The O-ring provides for a secure fit of the
end cap 25 over the end, of the body 20. The body 20 includes a pin 64 on
the exterior of the body 20 for aligning the end cap 28 and securely holding
the end cap 28 to the body 20.
[0039] The infrared welder 10 is assembled by inserting the reflector
assembly 22 into the receptacle region 50 of the body 20. The reflector
assembly 22 is positioned by aligning the detent 54 with the detent pin 52.
The end cap 28 is fitted over the first end of the body 20 such that the outer
rim of the primary reflector 24 is seated on the shoulder 58 of the secondary
reflector 30. The end cap 28 and body 20 fit together wherein an O-ring 62
is positioned in a circumferential detent in the body 20 and a complementary
detent in the end cap 28. The position of the end cap 28 is oriented by a pin
64 situated in the side of the body 20. The use of the pin 64 permits an end
cap 28 having an asymmetrical shape when required by design criteria.
[0040] A variation in the design for fitting the end cap 28 on the body
20, the body 20 may have threads on the exterior of the first end, and the
end cap 28 may have complementary threading in the interior of the end cap
rim 36.
[0041] In operation, a welding cycle begins when the parts 12, 14 are
in an overlaying position and the infrared welding apparatus 10 is positioned
over the area of the parts 12, 14 to be joined. The lamp 26 is energized and
the radiation emitted thereby is directed by the primary reflector 24 toward
the secondary reflector 30. The secondary reflector 30 directs the energy
through an aperture 32 in the secondary reflector 30 to the parts 12, 14 to be
joined. The lamp 26 is energized for a sufficient time to heat a localized
area
of the parts 12, 14 to a temperature at which the parts 12, 14 are plastically
deformable. The required heating time depends upon the power output of
the lamp 26 and the type and color of the plastic being heated. Using a 100
watt lamp 26 and white ABS plastic, for example, it has been found that it
takes approximately 7 seconds to the heat the plastic parts 12, 14 to 350-
400°F., the temperature at which it may easily be formed. Typically,
there is
an opening 16 in the plastic part 14 overlaying the second plastic part 12.
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
9
This permits the infrared energy to be focused at an area where the plastic
parts 12, 14 are to be joined. If there is no opening 16, the overlaying
plastic
part 14 has some transparency for the infrared radiation in order to allow the
infrared radiation to heat the overlaid plastic part 12. In a preferred
embodiment, the energy source is a 100 watt halogen lamp. The halogen
lamp 26 produces energy across a broad band including the infrared, and
rapidly heats the plastic to the desired temperature. As an option, after
heating areas of the plastic parts 12, 14 to a temperature sufficient to
plastically deform the areas, a press 80 is used to press and hold the plastic
parts 12, 14 together until the plastic parts 12, 14 fuse and resolidify. In
addition to welding, continuous welding is performed by moving the infrared
welder 10 at a controlled fixed rate.
[0042] An alternative use includes butt-welding or seam welding of
plastic parts,.wherein the welding is performed along edges of plastic parts
abutting one another.
[0043] The inner surfaces of the primary reflector 24 and the
secondary reflector 30 are highly reflective of the wavelengths of infrared
radiation emitted by the lamp 26. It has been found that a polished
aluminum or stainless steel surface has desirable reflective properties. The
end cap 28 may be machined from a billet of aluminum or stainless steel,
with the complex shape of the inner surface of the secondary reflector 30
being formed by a computer controlled milling machine. Preferably, a layer
of gold is deposited on the surfaces of the primary reflector 24 and the
secondary reflector 30. The gold is deposited by dip-plating, electro-plating,
or by any means that deposits a thin layer of gold on the surfaces of the
reflectors 24, 30. Preferably, the gold is deposited only on the surfaces of
the reflectors 24, 30, but in an alternative, as an example, the entire end
cap
28 may be dipped. Considerations for choosing the method of coating the
reflectors 24, 30 include balancing the cost of the method of coating the
reflectors 24, 30 with gold against the amount of gold used in the process of
coating. Gold has the desirable property of reflecting virtually all of the
energy in the infrared band thereby providing a very high efficiency for the
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
transfer of infrared energy from the lamp 26 to the surface of the parts 12,
14
to be joined.
(0044] In an alternative embodiment, the reflector assembly 22 and
the body 20 are an integrated unit, as shown in Figure 6. The primary
reflector 24 includes an aperture in the center of the reflector 24 for
insertion
of the lamp 26. The secondary reflector 30 is mounted in an end cap 28.
The end cap 28 is removably attached to the body 20 for easy access to the
lamp 26.
(0045] In an alternative embodiment, the infrared welding apparatus
10 includes a single reflector 66 having a convergent design. As shown in
Figure 7, the apparatus 10 includes a body 20, and a reflector assembly 22.
The reflector assembly 22 fits securely in the body, and an end cap is not
required. The single reflector 66 has a convergent design, and collects the
radiation from the lamp 26 and focuses the radiation to a point outside the
apparatus 10. The reflector assembly 22 includes a single reflector 66
having a first aperture 68, and a second aperture 70. The first aperture 68 is
an aperture through which the energy from the lamp 26 is focused, and the
second aperture 70 is for insertion of a lamp 26 into the reflector assembly
22. In one assembly variation, the first aperture 68 is of sufficient size for
the
passage of the lamp 26 through the aperture 68 for insertion into the second
aperture 70 with electrical connectors 42 extending beyond the end of the
assembly 22. If the aperture 68 is too small to admit lamp 26, the lamp 26
may be inserted into the second aperture 70 before the assembly 22 is
inserted into the body 20 of the apparatus 10, and having electrical
connectors 72 on the lamp extending beyond the assembly. The assembly
22 is inserted into a receptacle region 50 of the body 20 until contact is
made
between the electrical connectors 42 of the assembly 22 and electrical
connectors 46 in the body 20. The assembly 22 and body portion 20 may be
secured together by a friction fit with a detent at the fully seated position,
or
the assembly may have male threads formed on the exterior of the assembly
which mate with female threads formed in the receptacle region 50 in the
lower end of the body 20.
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
11
[0046] An alternative embodiment of the apparatus 10', as shown in
Figure 8, the primary reflector 24' has an ellipsoidal shape. The apparatus
10' has a central axis coincident with the major axis of the ellipse. The
primary reflector 24' is a surface of rotation of a segment of the ellipse
about
the central axis. The ellipsoidal shape directs the energy from a first focal
74
point to a second focal point 76. The incandescent lamp 26 is positioned
such that the filament in the lamp 26 is located substantially at the first
focal
point 74, with the primary reflector 24' in a surrounding configuration. The
primary reflector 24' is designed such that the position of the second focal
point 76 is substantially located at the center of the aperture 32 of the
secondary reflector 30'.
[0047] The apparatus 10', as shown in Figure 8, further includes a
light pipe 78. The light pipe 78 is, in this case, essentially integral with
the
end cap 28', but may be manufactured as a separate piece which is affixed
to the end cap 28' at the aperture 32 of the secondary reflector 30'. The
light pipe 78 is a rigid hollow cylindrical tube for directing the radiant
energy
converging on the second focal point 76 to the area being welded.
Preferably, the light pipe 78 includes a hollow insert 82 designed to fit
snugly
within the tube. The insert 82 is preferably coated with a layer of gold. Use
of the insert 82 allows a dip process for gold plating and requires less
material than would be the case if the entire end cap 28' were dip-plated.
[0048] The light pipe 78 may be up to one foot (30 cm) in length, with
a preferable length from about one inch (2.5 cm) to about four inches (10
cm). The light pipe 78 can be flexible to permit bending of the light pipe 78
in
order to direct the radiant energy. The material selected for the light pipe
78
is rigid enough to maintain the hollow tubular shape and allows for limited
bending of the light pipe 78. The light pipe 78 may be bent in an arc having
a radius of curvature of at least one meter.
[0049] Preferably the light pipe 78 is fabricated from a nickel shell or
copper tubing, but materials of fabrication include any material capable of
rigid, but flexible construction. The material must be capable of being coated
with a thin layer of gold, or of holding an insert 82 capable of being coated
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
12
with a thin layer of gold. The preferred materials of construction for the
insert
82 are nickel or copper tubing. The use of the insert 82 reduces the amount
of gold needed for coating the inner surface.
[0050] As shown in Figures 7, 9 and 11, an optional feature includes a
spacer 84. The spacer 84 is adjustably attached to the body 20 of the
apparatus 10. The spacer 84 provides for setting and maintaining the
appropriate distance from the apparatus 10 to the parts 12, 14 being joined.
The appropriate distance is the distance from the apparatus 10 to a plane
perpendicular to the axis of symmetry 34, and at the focal point for the
radiation emitted and focused from the apparatus 10. The spacer 84 may
optionally be marked with gradation lines forming a linear scale on the
spacer 84. The spacer 84 provides for a rapid and easy method of setting
the apparatus 10 the appropriate distance from the parts 12, 14 for welding,
and for a quick adjustment once calibration of the apparatus has been
performed. The spacer 84 may be a rod, or the spacer may have a plurality
of legs attached to the body 20 of the apparatus. In addition, the spacer may
include a loop attached to the end of the spacer 84 and oriented
perpendicular to the spacer 84, such that the loop is used to outline the
target region on the parts 12, 14 to be joined to facilitate rapid positioning
of
the infrared welder over the target region.
[0051] In another embodiment of the apparatus 10 as shown in
Figures 9 and 10; an infrared welder includes two primary reflectors 124 and
two lamps 126. The lamps 126 are disposed in a side-by-side relationship
around an axis of symmetry 134 and above a secondary reflector 130
generally similar to that described in Figures 1-3. The secondary reflector
130 is removable for access to the lamps 126 and replacement thereof.
Wth this embodiment, any number of lamps 126 may be disposed around
the axis 134, space permitting. A preferred lamp 126 is a halogen lamp. As
an alternative, halogen lamps are commercially available with the primary
reflector 124 in the lamp unit. The use of a commercially available lamp and
reflector unit provides for an energy source properly positioned within the
reflector. This also provides for convenient replacement of the lamps 126
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
13
and reflectors 124. An optional construction of this embodiment provides for
the secondary reflector 130 to be segmented such that each segment
substantially focuses radiation from an individual lamp 126. This multiple
lamp 126 and reflector 124 configuration may be desirable in order to
construct an infrared welding apparatus 10 having higher heat requirements.
(0052] In another alternate embodiment of the invention, as shown in
Figure 11, the apparatus 10 uses fiber optic cables 90. In this embodiment,
the lamp 26 is mounted in the reflector assembly 22. The reflector 24 directs
the energy from the lamp 26 to a convergent lens 92. The convergent lens
92 focuses the energy into a fiber optic cable 90. The fiber optic cable 90
extends from the convergent lens 92 and splits into a plurality of sub-cables
94 which have distal ends 96. The distal ends 96 are arrayed around and
directed at a localized area on the parts 12, 14 to be joined. Preferably, the
distal ends 96 are arrayed evenly around the area on the parts 12, 14 to be
joined. The energy travels along the cable 90, is split among the sub-cables
94, and exits the distal ends 96. Fiber optic cables are thin glass or plastic
filaments which conduct light by internal refraction, and are well known in
the
art.
[0053] The use of a heat lamp in an infrared welding device according
to the present invention provides a heat source with nearly instant on/off
control, thereby providing precise temperature control. The radiant heat
source heats only the area desired, thus achieving an overall efficiency of
approximately 80%. Commercially available infrared lamps are relatively
inexpensive and have lives on the order of 2000 hours, contributing further to
the economic advantage of the invention over the prior art. The use of
commercially available 100 watt lamps provide sufficient energy for most
plastics, but when greater energy is needed larger wattage lamps can be
used.
[0054] An optional feature of this invention is a press 80 attached to
the infrared welder 10. The press 80 is used to apply temporary pressure to
press the plastic parts 12, 14 together until the plastic resolidifies. As
shown
in Figure 12, the press 80 is in the interior of the apparatus 10. The press
80
CA 02457893 2004-02-11
WO 03/019983 PCT/US02/27377
14
is connected to two retractable arms 108 that straddle the lamp 26., The
arms 108 are connected to a plate 110, wherein the plate 110 is operatively
connected to an air cylinder 112. The arms 108 slide within arm-guides in
the reflector assembly 22 for moving the press 80 toward and away from the
workpieces 12, 14. The press 80 is actuated and presses against the plastic
'parts 12, 14 until the parts 12, 14 fuse. In an alternative, the press 80' is
disposed on an armature 102 pivotingly mounted on the outside of the
infrared welder 10, as shown in Figure 13. An air cylinder 104 is connected
to the apparatus 10 and has a vertically oriented drive piston 106 which is
connected to the armature 102. During the heating cycle of the infrared
welding operation, the infrared welder is lowered to an appropriate distance
from the workpieces 12, 14, and the press 80' is in a raised position wherein
it is pivoted outwardly and upward. After the workpieces 12, 14 have been
heated for a sufficient length of time to soften the area to be joined, the
air
cylinder 104 is operated to extend the piston 106 and the press 80' is
pivoted into position. The apparatus 10 is pressed against the workpieces
12, 14 to maintain the contact between the workpieces 12, 14, and held in
that position for a sufficient time the softened area to resolidify.
[0055] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be limited to
the disclosed embodiments but, on the contrary, is intended to cover various
modifications and equivalent arrangements included within the spirit and
scope of the appended claims, which scope is to be accorded the broadest
interpretation so as to encompass all such modifications and equivalent
structures as is permitted under the law.
