CA2457893A1

CA2457893A1 - Infrared welder

Info

Publication number: CA2457893A1
Application number: CA002457893A
Authority: CA
Inventors: Roger Miller; Andrew Vanklompenberg
Original assignee: Individual
Current assignee: Extol Inc
Priority date: 2001-08-27
Filing date: 2002-08-27
Publication date: 2003-03-06
Also published as: WO2003019983A1

Abstract

An apparatus for welding thermoplastic materials utilizes an incandescent lamp (26) for generating infrared energy which is concentrated into a beam and aimed at a work area adjacent to the output end of the apparatus. Infrared energy is collected and aimed by gold-plated reflectors (24, 30), or, alternatively, optical light pipes (78).

Description

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.

[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 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;

[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 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 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 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 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 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.

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 transfer of infrared energy from the lamp 26 to the surface of the parts 12, 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.

[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 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 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 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 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 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.

Claims

What is claimed is:

1. An apparatus for welding thermoplastic parts comprising:
an energy source for generating energy in the infrared band;
and an energy directing means for directing energy from the source to a localized area on the thermoplastic parts.

2. The welding apparatus as defined in claim 1 wherein the energy source is at least one incandescent lamp producing illumination in the infrared band.

3. The welding apparatus as defined in claim 2 wherein the energy directing means comprises at least one optical reflector.

4. The welding apparatus as defined in claim 3 wherein the energy directing means comprises:
a housing;
a primary reflector mounted in the housing, surrounding the energy generating means and directing the energy in a uniform direction;
and a secondary reflector having a central aperture and focusing the energy directed from the primary reflector through the central aperture and to the localized area outside the housing.

5. The welding apparatus as defined in claim 4 wherein the primary and secondary reflectors have a reflective surface covered by a layer of gold.

6. The apparatus as defined in claim 4 wherein the secondary reflector further comprises a tubular extension with a reflective hollow cylindrical interior.

7. The apparatus as defined in claim 6 wherein the hollow cylindrical interior is covered by a layer of gold.

8. The welding apparatus as defined in claim 4 further comprising a lamp holder, wherein the lamp holder provides electrical contact between the lamp and an electrical receptacle.

9. The welding apparatus as defined in claim 8 wherein the lamp holder comprises;
a first holder part including apertures for admitting electrical leads from the lamp;
a second holder part including apertures for admitting electrical contacts from the electrical receptacle; and a circuit stamp disposed between the first holder part and second holder part, and provides electrical communication between the lamp and the electrical contacts wherein the lamp holder is sized to fit the end of the primary reflector unit.

10. The welding apparatus as defined in claim 9 further comprising an air fitting, wherein the air fitting is attached to an aperture in the housing.

11. The welding apparatus as defined in claim 10 wherein the lamp holder includes apertures for the passage of air.

12. The welding apparatus as defined in claim 11 wherein the secondary reflector includes at least one pore.

13. The welding apparatus as defined in claim 3 wherein the at least one reflector is a single reflector in a surrounding relationship to the energy source, whereby the single reflector is a surface of revolution, and is defined by a curve that focuses the energy from the energy source onto the localized area.

14. The welding apparatus as defined in claim 3 wherein the energy directing means comprises:
a primary reflector mounted in the housing, surrounding the energy generating means and directing the energy toward in a uniform direction;
a plurality of fiber optic cables for focusing the energy; and a lens for focusing the energy from the primary reflector into the fiber optic cables.

15. The welding apparatus as defined in claim 2 wherein the at least one incandescent lamp is a halogen lamp.

16. The welding apparatus as defined in claim 1, further comprising a spacer for providing the correct spacing of the apparatus from the focal point.

17. The welding apparatus as defined in claim 16 wherein the spacer is a rod with calibrations along the length of the rod.

18. The welding apparatus as defined in claim 1 further comprising means for pressing thermoplastic parts together.

19. A welding apparatus for welding thermoplastic parts comprising:
a housing having a longitudinal axis;
at least one incandescent lamp mounted in the housing for generating energy in the infrared band, wherein the at least one incandescent lamp is a halogen lamp; and at least one reflector mounted in the housing surrounding the at least one incandescent lamp for directing the infrared energy in a substantially uniform direction and focusing the infrared energy to a localized area located outside the apparatus, wherein the at least one reflector has a reflective surface covered by a layer of gold.

20. The apparatus as defined in claim 19 further including a second reflector in axially spaced relation to said one reflector for receiving energy therefrom and directing said energy to a spot external thereto.

21. The apparatus as defined in claim 20 wherein the second reflector further comprises a tubular extension with a reflective hollow cylindrical interior.

22. The apparatus as defined in claim 19 further comprising means for pressing the thermoplastic parts together.

23. A welding apparatus for welding thermoplastic parts, the apparatus comprising:
at least one incandescent lamp for generating energy in the infrared band;
a primary reflector surrounding the at least one incandescent lamp for directing the energy in a substantially uniform direction; and a secondary reflector having a central aperture and focusing the energy directed from the primary reflector through the central aperture to a focal point located outside the secondary reflector;
wherein the primary and secondary reflectors have a reflective surface covered by a layer of gold.

24. The welding apparatus as defined in claim 23 further comprising a lamp holding unit including a circuit stamp disposed within the lamp holding unit for providing electrical connection between the incandescent lamp and leads to an electrical receptacle.